Apparatus and method for preventing unauthorized use of information recorded on an information recording medium

An information recording medium includes a lead-in area and a data recording area. Key information is recorded in the lead-in area. Scrambled data is recorded in the data recording area. The scrambled data is descrambled based on the key information.

TECHNICAL FIELD
 The present invention relates to an information recording medium for
 recording information signal containing program data, audio information
 and video information, an information reproducing device for reproducing
 the information recorded in the information recording medium and a method
 for reproducing the information.
 BACKGROUND ART
 A floppy disk and a CD-ROM (Compact Disk-Read Only Memory) are
 conventionally known as an information recording medium for program data,
 audio information and video information. In particular, the CD-ROM is
 widely used for the distribution of various softwares because of its large
 capacity of more than 600 MB and low production cost.
 On the other hand, the promotion of high speed of a personal computer in
 recent years has increased the demand for outputting video and audio data
 (hereinafter, referred to as AV data) on the personal computer. For
 example, a digital data file where data is compressed by video image
 compression system called MPEG 1 (Moving Picture Experts Group) is
 recorded on CD-ROM, and an application for distributing such a CD-ROM has
 been increasingly available. However, since the MPEG 1 system generally
 compresses video data which requires a large capacity at a high
 compression ratio, quality of video images is significantly degraded.
 Therefore, the MPEG 1 is unsuitable for use where high quality in video
 images is required, such as movies or the like.
 In recent years, development for recording high quality video data on an
 optical disk having a large capacity close to 5 GB, using a higher
 performance video image compression system called MPEG 2 system has been
 pursued. Capitalizing on the large capacity, the optical disk called DVD
 (Digital Video Disk) can record high quality digital AV data for two hours
 or more, and thus greatly expected as an AV data recording medium of the
 next generation. On the other hand, the DVD is expected to allow for
 reproduction of high quality AV data on a personal computer by a DVD drive
 for reproducing DVD in connection to the personal computer. In addition,
 the DVD is expected to substitute for the CD-ROM as a medium for
 distributing calculator software.
 However, when the DVD drive as a peripheral device for the personal
 computer, commercially available, digital data recorded in the DVD may be
 output to the personal computer, and may easily be copied on a rewriting
 type medium, such as a hard disk nor an MO (Magneto-Optical Disk). Easy
 copying of the digital AV data causes problems such as illegal copying of
 the AV data recorded in the DVD without the permission of the copyright
 holder and distribution of altered AV data. This makes it extremely
 difficult to protect the copyright. This brings about a disadvantage not
 only to the copyright holder of the data, but also possibly to users in
 the case where the copyright holder sets the price in view of unauthorized
 copies being made, or does not produce disks for fear of alteration of the
 data. Hereinafter, the problem described above is referred to as a first
 problem.
 On the other hand, as uses for the information recording medium where the
 AV data is recorded, a variety of uses are considered. In some uses among
 these uses, the fact that the information recording medium can be
 reproduced in any reproducing device causes a problem. In such a use, it
 is preferable to differentiate a reproducing device capable of reproducing
 and a reproducing device incapable of reproducing. For example, for disks
 generally called "karaoke" disks where video data including words
 corresponding to reproduced music is recorded, there exist two types of
 disks: disks privately used in households (hereinafter, referred to as
 consumer disks) and disks used in a facility such as where customers enjoy
 karaoke for a predetermined charge (hereinafter, referred to as industrial
 disks). Since the industrial disks are produced under the premise that
 they are supplied in a large quantity to limited users, they are supplied
 at a low price. On the other hand, consumer disks are sold at a high price
 due to individual sale.
 However, in the case where the industrial disks and the consumer disks have
 entirely the same format, there is a possibility of selling the industrial
 disks as the consumer disks at low price in the consumer market. This
 prevents the consumer disks from being distributed in a proper price in
 the market, thus resulting in a disadvantage for disk manufacturers and
 users who purchase the consumer disks through the normal route. Therefore,
 it is desirable to differentiate the reproducing device capable of
 reproducing the consumer disks from that capable of reproducing industrial
 disks in such a use. For another example, a disk having the content which
 causes an ethical problem may be reproduced. The criterion which
 determines whether or not the disk is ethical is varied from country to
 country. Therefore, a disk to be reproduced in a certain country may not
 be desired to be reproduced in another country. Therefore, a mechanism is
 required which allows a disk which causes an ethical problem to be
 reproduced only in a specific country where the sale thereof is permitted.
 As described above, there has been a problem that the reproducing device
 capable of reproduction and the reproducing device incapable of
 reproduction cannot be differentiated depending on the use. Hereinafter,
 this problem is referred to as a second problem.
 As one means for solving the two aforementioned problems, there is a method
 of scrambling (encrypting) data to be recorded in the information
 recording disk for recording. More specifically, regarding the first
 problem, at the time of a copying operation in the personal computer, data
 scrambled based on a key is transmitted back, and a key for descrambling
 is not transmitted back, thus preventing the copying operation (the
 copying operation is performed, but since the descrambling is not
 effected, the copying operation makes no sense).
 Furthermore, regarding the second problem, it is possible to classify a
 device capable of descrambling and a device incapable of descrambling by
 producing disks which are differently scrambled depending on the contents
 of the disks. Thus, the scrambling (encrypting) of the recorded data is
 effective on the two aforementioned problems. However, another problem is
 a method for descrambling data or how to specify a key for descrambling
 data.
 As a first conventional example for encrypting in a data field, a system of
 recording an encrypting key in a main data field of a sector different
 from an encrypted data sector was proposed in a CD-ROM in FIG. 3 of
 Japanese Laid-Open Patent Publication No. 7-249264. In this conventional
 example, data reproduction is realized by recording encrypted data and an
 encrypting key thereof in the CD-ROM at the time of recording, and
 decrypting the encrypted data after executing a reading command of the
 encrypting key from a personal computer to a reproducing device at the
 time of reproducing. This method has an advantage in that the encrypting
 key can be easily changed.
 Furthermore, as a second conventional example, as shown in FIG. 3 of
 Japanese Laid-Open Patent Publication No. 7-85574, a system of recording
 an encrypting key in an area in a disk which the optical head of the
 reproducing device does not scan was proposed. In this conventional
 example, since the encrypting key is prevented from being read from a
 general personal computer, the encrypting key is not copied in a copying
 operation, and thus an illegal copying operation makes no sense.
 However, since the encrypting key of the first conventional example is
 recorded in the main data field of the sector, it is possible to easily
 read the encrypting key used at the time of recording the disk from a
 general personal computer. Therefore, since users can read the encrypting
 key and the encrypted data, it is highly possible to decrypt the
 encrypting.
 Furthermore, in the second conventional example, the encrypting key is
 recorded in the area which the optical head of the reproducing device does
 not scan. In order to read the encrypting key, therefore, reading means
 dedicated to reading the encrypting key is required, in addition to
 reading means for reading data from the data recorded area, thus causing a
 problem.
 In both of the first and second conventional examples, data is encrypted
 with a single encryption key, thereby failing to ensure a sufficient
 security level in the case where the encryption key is read out by a third
 party.
 The present invention has an objective of providing an information
 recording medium having a data structure which ensures the prevention of
 the content recorded in the information recording medium from being
 illegally copied so as to realize secured copyright protection, an
 information reproducing device capable of reproducing data from the
 information recording medium without providing a special data reading
 means, and solving the first and second problems, and a method for
 reproducing information.
 DISCLOSURE OF THE INVENTION
 An information recording medium according to the present invention includes
 a lead-in area and a data recording area. Key information is recorded in
 the lead-in area. Scrambled data is recorded in the data recording area.
 The scrambled data is descrambled based on the key information.
 According to another aspect of the invention, an information recording
 medium includes a lead-in area and a data recording area. First key
 information is recorded in the lead-in area. Second key information and
 scrambled data are recorded in the data recording area. The scrambled data
 is descrambled based on information obtained by converting the second key
 information based on the first key information.
 In one embodiment of the invention, the data recording area is divided into
 a plurality of sectors. Each of the plurality of sectors includes a sector
 header field where information for identifying the sector is recorded and
 a main data field where the scrambled data is recorded. The second key
 information is recorded in the sector header field.
 In another embodiment of the invention, the second key information is
 encrypted by the first key information, and the information is obtained by
 decrypting the encrypted second key information.
 In still another embodiment of the invention, the first key information is
 encrypted by master key information.
 In yet another embodiment of the invention, a plurality of first key
 information is recorded in the lead-in area, and the plurality of first
 key information are encrypted by a plurality of different master key
 information.
 In another embodiment of the invention, a scramble flag for indicating
 whether or not data recorded in the data recording area is scrambled is
 further recorded in the information recording medium.
 In still another embodiment of the invention, the data recording area is
 divided into a plurality of sectors. Each of the plurality of sectors
 includes a sector header field where information for identifying the
 sector is recorded and a main data field where the scrambled data is
 recorded. The scramble flag is recorded in the sector header field.
 In yet another embodiment of the invention, the data recording area
 includes an area where a plurality of files are recorded and a file
 management area where information for managing the plurality of files is
 recorded, and the scramble flag is recorded in the file management area.
 In another embodiment of the invention, mutual authentication key
 information for performing mutual authentication between a reading device
 for reading the scrambled data and a decoding device including a
 descramble circuit for descrambling the scrambled data is further recorded
 in the lead-in area.
 In still another embodiment of the invention, the information is an initial
 value for generating a random number sequence, and the scrambled data is
 descrambled by performing a logical operation to the random number
 sequence.
 In yet another embodiment of the invention, the data recording area is
 divided into a plurality of sectors. Each of the plurality of sectors
 includes a sector header field where information for identifying the
 sector is recorded and a main data field where the scrambled data is
 recorded. Information for identifying use of the information recording
 medium is recorded in the sector header field.
 According to another aspect of the invention, an information reproducing
 device includes a reading circuit for reading scrambled data and key
 information to be used for descrambling the scrambled data from an
 information recording medium; and an authentication circuit for
 authenticating to transmit information corresponding to the key
 information to the decoding device before transmitting the scrambled data
 to the decoding device including a descramble circuit for descrambling the
 scrambled data.
 In one embodiment of the invention, the information recording medium
 includes a lead-in area and a data recording area. Key information
 includes first key information recorded in the lead-in area and second key
 information recorded in the data recording area.
 According to another aspect of the invention, an information reproducing
 device includes an authentication circuit for authenticating key
 information from a reading device before receiving scrambled data from the
 reading device for reading the scrambled data and the key information to
 be used for descrambling the scrambled data from an information recording
 medium; and a descramble circuit for descrambling the scrambled data
 received from the reading device.
 In one embodiment of the invention, the information recording medium
 includes a lead-in area and a data recording area. The key information
 includes first key information recorded in the lead-in area and second key
 information recorded in the data recording area.
 In another embodiment of the invention, the descramble circuit descrambles
 the scrambled data based on information obtained by converting the second
 key information based on the first key information.
 According to another aspect of the invention, an information reproducing
 device includes a reading circuit for reading scrambled data and key
 information to be used for descrambling the scrambled data from an
 information recording medium; a decoding section including a descramble
 circuit for descrambling the scrambled data; and an authentication circuit
 for authenticating to transmit information corresponding to the key
 information to the decoding section before transmitting the scrambled data
 to the decoding section.
 In one embodiment of the invention, the information recording medium
 includes a lead-in area and a data recording area. The key information
 includes first key information recorded in the lead-in area and second key
 information recorded in the data recording area.
 In another embodiment of the invention, the descramble circuit descrambles
 the scrambled data based on information obtained by converting the second
 key information based on the first key information.
 In still another embodiment of the invention, a scramble flag for
 indicating whether or not data recorded in the data recording area is
 scrambled is further recorded in the information recording medium. The
 information reproducing device further includes a control circuit for
 controlling whether or not the authentication circuit is to be activated
 depending on the scramble flag.
 In yet another embodiment of the invention, authentication by the
 authentication circuit is performed by using a predetermined function.
 In another embodiment of the invention, authentication by the
 authentication circuit is performed by using information changing over
 time.
 In still another embodiment of the invention, the authentication circuit
 generates bus key information in the case where authentication processing
 is normally ended, and encrypts the first key information and the second
 key information using the bus key information.
 In yet another embodiment of the invention, the authentication circuit
 decrypts the encrypted first key information and the encrypted second key
 information encrypted using the bus key information.
 According to another aspect of the invention, an information reproduction
 method for reproducing scrambled data using a reading device for reading
 scrambled data and the key information to be used for descrambling the
 scrambled data from an information recording medium and a decoding device
 including a descramble circuit for descrambling the scrambled data
 includes the steps of performing mutual authentication processing between
 the reading device and the decoding device; generating bus key information
 common to the reading device and the decoding device in the case where the
 mutual authentication processing is normally ended between the reading
 device and the decoding device; encrypting the key information in
 accordance with the bus key information; and transmitting the encrypted
 key information from the reading device to the decoding device.

BEST MODE FOR CARRYING OUT THE INVENTION
 Hereinafter, the present invention will be described by way of embodiments
 with reference to the accompanying drawings.
 (First Embodiment)
 FIG. 1 shows a data structure of an information recording medium according
 to the present invention. Hereinafter, a disk will be described as an
 example of the information recording medium. However, the information
 recording medium of the present invention is not limited to the disk, but
 any information recording mediums.
 Generally, information recording areas where some information is recorded
 on a disk are roughly classified into a lead-in area where control
 information is mainly recorded and a data recording area where user data
 is recorded. In addition, the data recording area is generally partitioned
 into a unit referred to as a sector. Herein, a disk reproducing device can
 directly access the lead-in area, but devices other than the disk
 reproducing device (e.g., a personal computer) cannot access the lead-in
 area.
 Each sector includes a sector header field where a sector ID (Identifier)
 for identifying the sector or the like is recorded, a user data field
 where user data is recorded, and an ECC (Error Correction Code) field
 where a code for correcting readout errors at the time of reproduction is
 recorded. A "sector header field" is a field where control information
 used by a reproduction apparatus is recorded, and it is difficult to
 directly read the field by an external unit, such as, a PC. In this
 embodiment, the user data recorded in the user data field in the sector is
 subjected to scramble-processing. Therefore, it is necessary to identify
 the scramble-processing method which is performed with respect to the user
 data in order for the information reproducing device to correctly
 reproduce the user data from the disk shown in FIG. 1.
 In a predetermined location in the lead-in area of the disk in FIG. 1,
 information which determines a scramble-processing method which is
 performed with respect to the user data (hereinafter, referred to as
 "scramble information" in this specification) is recorded. The information
 reproducing device reads the area where the scramble information is
 recorded, interprets the scramble information and performs
 descramble-processing in accordance with the scramble information with
 respect to the user data. Thus, it is possible to correctly reproduce the
 user data.
 Hereinafter, an example of a scramble-processing method which is generally
 known will be described with reference to FIG. 9.
 Portion (a) of FIG. 9 shows that one sector consists of a sector header
 field (where a sector ID for identifying the sector is included), a user
 data field of 2048 bytes and an ECC field. A data byte sequence D.sub.0,
 D.sub.1, . . . and D.sub.2047 is recorded in the user data field. The data
 byte sequence D.sub.0, D.sub.1, . . . and D.sub.2047 is obtained by a
 logical operation of a data byte sequence D'.sub.0, D'.sub.1, . . . and
 D'.sub.2047 to be recorded (before scramble-processing) and a random
 number sequence S.sub.0, S.sub.1, . . . and S.sub.2047. For example, the
 logical operation can be an exclusive logical sum. The random number
 sequence S.sub.0, S.sub.1, . . . and S.sub.2047 is uniquely determined by
 a supplied initial value.
 It will be understood that throughout this disclosure, the term "random
 number sequence" is known in the art as a "pseudo-random number sequence".
 In order to obtain the random number sequence S.sub.0, S.sub.1, . . . and
 S.sub.2047, based on a predetermined bit string in the sector (e.g., three
 bits in the predetermined location in the sector ID), a table as shown in
 portion (b) of FIG. 9 is referred to. For example, in the case where the
 three bits in the predetermined location in the sector ID are (0, 0, 1),
 100Fh is obtained as the initial value according to the table, and the
 random number sequence B.sub.0, B.sub.1, . . . and B.sub.2047
 (corresponding to S.sub.0, S.sub.1, . . . and S.sub.2047) is uniquely
 determined.
 As a method for generating the random number sequence S.sub.0, S.sub.1, . .
 . and S.sub.2047 from the supplied initial value, for example, a method of
 employing a shift register as shown in portion (c) of FIG. 9 is known.
 As a scramble-processing method, it is possible to employ other methods
 such as a method of replacing a predetermined bit in the byte sequence in
 the user data. The following description is made by taking the
 scramble-processing method described with reference to FIG. 9 as an
 example.
 FIG. 2 shows a structure of a scramble information recorded in a
 predetermined location in the lead-in area in the disk shown in FIG. 1.
 As shown in portion (a) of FIG. 2, in this example, the scramble
 information is an identifier for designating a table for providing an
 initial value for a random number sequence to be used in
 scramble-processing. It is assumed that information for specifying the
 scramble-processing method other than the table is previously defined.
 For example, the content of the scramble information of (1, 0) indicates
 that, among four tables previously defined as shown in portion (b) of FIG.
 2, table 2 is used for the scramble-processing. The information
 reproducing device has a memory storing the four tables shown in portion
 (b) of FIG. 2, and switches the table to be used for descramble-processing
 in accordance with the scramble information. Thus, it is possible to
 correctly execute the descramble-processing with respect to the user data.
 FIG. 3 shows another data structure of the disk according to the present
 invention. An initial value table is directly recorded in the lead-in area
 in the disk shown in FIG. 3. The user data which is subjected to
 scramble-processing with the random number sequence generated by using the
 initial value table is recorded in the data recording area in the disk.
 Herein, it is assumed that other parameters which the scramble-processing
 method shown in FIG. 3 has are uniquely determined in advance.
 The information reproducing device reads the initial value table recorded
 in the lead-in area in the disk, and interprets the initial value table.
 Thereafter, the information reproducing device sets a
 descramble-processing procedure in accordance with the initial value
 table, and descrambles the user data in accordance with the
 descramble-processing procedure. Thus, it is possible to correctly
 reproduce the scrambled user data.
 Furthermore, the disk can be reproduced by an information reproducing
 device which only has a specific descramble-processing procedure, only in
 the case where the initial value table of the disk is matched with that of
 the information reproducing device. It is impossible to correctly
 reproduce in other cases than that.
 The embodiment described above has demonstrated a method of changing the
 initial value table of the random number sequence in the
 scramble-processing method shown in FIG. 9. However, the
 scramble-processing method shown in FIG. 9 is not necessarily used, and a
 totally different scramble-processing method can be used. Furthermore, in
 the scramble-processing method shown in FIG. 9, a variety of parameters
 which can be changed exist, other than the initial value table (e.g., how
 to select a bit string for reference to the initial value table and a
 structure of a shift register for generating random numbers or the like).
 Thus, it is possible to supply an identifier to each of the changeable
 parameters and a combination thereof.
 As described above, according to the information recording medium of the
 present invention, it is possible to change the scramble-processing method
 depending on the use and whether or not copying is permitted. As a result,
 illegal reproduction (e.g., reproduction of an industrial disk by a
 consumer disk reproducing device) and illegal copying can be prevented.
 (Second Embodiment)
 FIG. 4 shows a structure of an information reproducing device according to
 the present invention. The information reproducing device includes a host
 computer 1 and a disk reproducing device 2 for reproducing data recorded
 in a disk 3.
 The host computer 1 includes an interface section (I/F section) 4, an AV
 decoder 6 for decoding video information so as to have a form in which the
 video information can be displayed, a video board 8 for supplying the
 video information to a display device 7, a CPU 10 and an internal memory
 11 such as a DRAM (Dynamic Random Access Memory). The video board 8, the
 CPU 10 and the internal memory 11 are interconnected via a data bus 9. The
 output of the video board 8 is connected to the display device (output
 device) 7. A hard disk drive 12 is connected to the interface section 4.
 A disk reproducing device 2 includes an interface section 5; a data
 reproduction section 13 including a mechanism for reading data from a disk
 3, a signal processing circuit, a controller and the like; and a
 microprocessor 14 for controlling the disk reproducing device 2.
 The host computer 1 and the disk reproducing device 2 are connected via the
 interface sections 4 and 5. For example, the interface sections 4 and 5
 can be connected by an existing interface such as an SCSI (Small Computer
 System Interface), an ATAPI (At Attachment Packet Interface) or the like,
 or a specially defined interface for its own.
 The disk reproducing device 2 reads scramble information recorded in the
 lead-in area in the disk 3 at the time of reset of the disk reproducing
 device 2 and at the time of replacement of the disk 3, interprets the
 scramble information and sets a descramble-processing procedure in
 accordance with the scramble information in the data reproduction section
 13.
 In order to display the user data recorded in the data recording area in
 the disk 3 in the output device 7, the host computer 1 issues a
 reproduction only command (hereinafter, referred to as a PLAY AV command)
 to the disk reproducing device 2 via interface sections 4 and 5. In
 response to the PLAY AV command, the disk reproducing device 2 transmits
 the user data which is subjected to the descramble-processing in
 accordance with the scramble information to the host computer 1.
 The interface section 4 of the host computer 1 does not transmit the user
 data received from the disk reproducing device 2 by using the PLAY AV
 command to the data bus 9, but only transmits to the AV decoder 6.
 Therefore, it is impossible to record the user data obtained by using the
 PLAY AV command in a rewritable medium such as the hard disk drive 12
 connected to the host computer 1.
 The host computer 1 issues a data readout command (hereinafter, referred to
 as READ command) in the case where it is necessary to record the user data
 recorded in the data recording area in the disk 3 to the hard disk drive
 12 and the internal memory 11. In response to the READ command, the disk
 reproducing device 2 determines whether or not copying of the disk 3 is
 permitted, based on previously retained scramble information. The disk
 reproducing device 2 behaves differently depending on whether or not the
 scramble system specified by the scramble information is a type whose
 copying is permitted.
 In the case where the disk reproducing device 2 determines that copying of
 the disk 3 is permitted, correct user data which has been subjected to the
 descramble-processing in accordance with the scramble information read
 from the lead-in area in the disk 3, at the time of the start-up operation
 of the disk reproducing device 2, is transmitted to the host computer 1.
 On the other hand, in the case where the disk reproducing device 2
 determines that the copying of the disk 3 is prohibited, erroneous user
 data which has been subjected to descramble-processing inconsistent with
 the scramble information is transmitted to the host computer 1.
 Alternatively, it is possible to prevent the disk reproducing device 2
 from transmitting back correct data to the host computer 1 by conducting
 an error processing or the like. Thus, illegal copying can be prevented.
 There are a variety of methods for obtaining information whether or not
 copying of the disk 3 is permitted (hereinafter, referred to as copy
 permission information). For example, in the case where the copy
 permission information is recorded in a predetermined area in the disk 3,
 the disk reproducing device 2 can read the copy permission information
 from the predetermined area in the disk 3. Alternatively, in the case
 where the scramble-processing system is limited, depending on the copy
 permission information, the copy permission information can be specified
 by the read scramble information.
 Alternatively, the copy permission information can be represented by a part
 of the scramble information. For example, in the case where the scramble
 information consists of a plurality of bits, it is possible to allow one
 bit of the plurality of bits to represent the copy permission information.
 Thus, the scramble information can be used in order to definitively
 differentiate the scramble system for data which is permitted to be copied
 from the scramble system for data which is prohibited from being copied.
 Therefore, by reading the scramble information from the disk 3, it is
 possible to determine whether or not copying is permitted. In the
 following description, copy permission information is represented by a
 part of the scramble information.
 FIG. 5 shows another structure of an information reproducing device
 according to the present invention. In the information reproducing device
 in FIG. 5, the AV decoder 6 and the interface section 4 which are
 independent from each other in the host computer 1 in FIG. 4 are
 integrated. The structure of other components is the same as that of the
 information reproducing device in FIG. 4.
 When a PLAY AV command is issued from the host computer 1, the user data
 having been subjected to the descramble-processing in accordance with the
 scramble information is transmitted from the disk reproducing device 2 to
 the host computer 1. The user data is AV-decoded by the AV decoder 6, and
 then directly input to the video board 8. Other operations are the same as
 those in the information reproducing device in the embodiment described
 with reference to FIG. 4.
 FIG. 6 shows another structure of the information reproducing device
 according to the present invention The information reproducing device in
 FIG. 6 includes an interface section 4b integrated with an AV decoder 6
 and an interface section 4a which is independent of the interface section
 4b. The structure of other components is the same as that of the
 information reproducing device in FIG. 5.
 A PLAY AV command is only issued from the interface section 4b in the AV
 decoder 6. On the other hand, a READ command is issued from the interface
 section 4a independent of the interface section 4b. Since the other
 operations are the same as those in the information reproducing device in
 the embodiment described with reference to FIG. 4, the explanation will be
 omitted.
 FIG. 7 shows another structure of the information reproducing device
 according to the present invention. In the information reproducing device
 in FIG. 7, an AV decoder 6 for converting the form of data to a form in
 which the data can be displayed is incorporated into the disk reproducing
 device 2. Therefore, it is not necessary to connect the disk reproducing
 device 2 to the host computer 1.
 Hereinafter, the operation of the information reproducing device of this
 structure will be described. In the disk reproducing device 2 in FIG. 7, a
 microprocessor 14 reads scramble information from the disk shown in FIG.
 1, interprets the scramble information and performs descramble-processing
 to the user data in accordance with the scramble information. The user
 data having been subjected the descramble-processing is supplied to the AV
 decoder 6. The user data is AV-decoded by the AV decoder 6, and outputs to
 the output device 7. Thus, it is possible to reproduce the user data
 recorded in the disk 3.
 However, in the case where scramble information, which is not preferable to
 be reproduced by the disk reproducing device 2, is recorded on the disk 3,
 it is possible for the disk reproducing device 2 not to perform correct
 reproduction. For example, it is assumed that the disk 3 is an industrial
 disk for use in Karaoke. In this case, in the case where the disk 3 is
 mounted on a consumer disk reproducing device, it is possible to prevent
 the consumer disk reproducing device from performing reproduction of the
 data recorded in the disk 3. This is because the consumer disk reproducing
 device can determine from the scramble information recorded in the disk 3
 whether or not the scramble-processing method is used for the consumer
 disk. Thus, by restricting the scramble-processing method which can be
 used, depending on the use of the disk 3, it is possible for the disk
 reproducing device 2 to determine whether or not the data recorded in the
 disk 3 should be reproduced, based on the scramble information.
 Furthermore, for a disk reproducing device which can perform only a
 specific descramble-processing, by producing a disk where data is
 scrambled by a scramble method not corresponding to the
 descramble-processing is recorded, it is possible to prevent the disk
 reproducing device from reproducing data recorded in the disk.
 FIG. 8 shows a structure of an information reproducing device according to
 the present invention. The information reproducing device includes a host
 computer 1 and a disk reproducing device 11. The host computer 1 is not
 shown in FIG. 8. The structure of the host computer 1 is the same as those
 of the host computers 1 in FIGS. 4 to 6.
 The disk reproducing device 11 includes an interface section (IF section)
 5, a data reproduction section 13 for reading data recorded in the disk 3,
 a microprocessor 14 for controlling the disk reproducing device 11, a
 descramble circuit section 15, a demodulation and error correction section
 16, a ROM (Read Only Memory) 17 for storing a program which is to be
 executed by the microprocessor 14 or the like, and a data processing RAM
 (Random Access Memory) 20. The interface section 5, the data reproduction
 section 13, the microprocessor 14, the descramble circuit section 15, the
 demodulation and error correction section 16 and the data processing RAM
 20 are interconnected via an internal data bus 19. The descramble circuit
 section 15 includes an initial value table storing memory 18.
 The microprocessor 14 reads the scramble information from the disk 3 at the
 time of introduction of the power or the replacement of the disk 3, and
 interprets the scramble information.
 In the case where the disk 3 has the data structure shown in FIG. 2, the
 microprocessor 14 selects one initial value table from a plurality of
 initial value tables previously stored in the ROM 17 in accordance with
 the content of the scramble information. The microprocessor 14 allows a
 selected initial value table to be stored in the initial value table
 storing memory 18 in the descramble circuit section 15. The initial value
 table storing memory 18 can be, for example, a RAM. Alternatively, in the
 case where the initial value table storing memory 18 is a ROM, a plurality
 of initial value tables can be previously stored in the ROM.
 When the host computer 1 issues a PLAY AV command, the PLAY AV command is
 input to the microprocessor 14 via the interface section 5 in the disk
 reproducing device 2. In response to the PLAY AV command, the
 microprocessor 14 instructs the descramble circuit section 15 so as to
 perform descramble-processing with respect to the scrambled user data. The
 descramble circuit section 15 performs the descramble-processing in
 accordance with the initial value table stored in the initial value table
 storing memory 18. The data having been subjected to the
 descramble-processing is transmitted to the host computer 1 via the
 interface section 5. Thus, the data recorded in the disk 3 can be
 reproduced.
 On the other hand, when the host computer 1 issues a READ command, the READ
 command is input to the microprocessor 14 via the interface section 5 in
 the disk reproducing device 11. At this time, the microprocessor 14
 determines from the scramble information previously read from the disk 3
 whether or not copying is permitted in the scramble system. In the case
 where the microprocessor determines that copying is prohibited, an initial
 value table different from the initial value table corresponding to the
 scramble information is set in the descramble circuit section 15.
 Alternatively, the microprocessor 14 can transmit back an error to the
 host computer 1 without setting the initial value table in the descramble
 circuit section 15. Thus, it is possible to prevent data recorded in the
 disk 3 from being reproduced.
 Furthermore, in the case where the microprocessor 14 determines from the
 scramble information that copying is permitted and in the case where the
 disk 3 has the data structure shown in FIG. 3, the microprocessor 14 reads
 an initial value table from the lead-in area in the disk 3, and allows the
 initial value table to be stored in the initial value table storing memory
 18 in the descramble circuit section 15. The initial value table storing
 memory 18 is rewritable memory (e.g., an RAM). The description of other
 processings is omitted because they are the same as those in the case
 where the disk 3 has the data structure shown in FIG. 2.
 As described above, according to the information reproducing device of the
 present invention, it is possible to change the descramble-processing
 method depending on the scramble information recorded in the information
 recording medium. Thus, it is possible to correctly reproduce data
 scrambled by a plurality of kinds of different scramble-processing
 methods.
 Furthermore, according to the information reproducing device of the present
 invention, it is possible to determine whether or not to reproduce the
 data recorded in the information recording medium depending on the
 scramble information recorded in the information recording medium. As a
 result, illegal copying can be prevented, and thus the copyright of the
 data recorded in the information recording medium can be protected.
 (Third Embodiment)
 Portion (a) of FIG. 10 shows a data structure of an information recording
 medium according to the present invention. The information recording area
 where some data is recorded on the information recording medium includes a
 lead-in area, a data recording area and a lead-out area. In the lead-in
 area, information necessary for the information reproducing device to
 reproduce the information recording medium is recorded. In the data
 recording area, primarily, data such as program data useful for the user
 and AV data is recorded.
 Portion (b) of FIG. 10 shows a data structure of a control data area
 recorded in the lead-in area. The control data area includes a physical
 information sector and a scramble information sector. In the physical
 information sector, physical data of the disk such as a disk diameter, a
 disk structure, a recording density or the like are recorded. In the
 scramble information sector, information on a scramble system which has
 been used on the data recorded in the data recording area of the
 information recording medium or the like is recorded. The scramble
 information sector is referred to in order for the information reproducing
 device to perform descramble-processing. The scramble information sector
 will be described in detail with reference to the accompanying drawings
 later.
 Portion (c) of FIG. 10 shows a data structure of a volume-file management
 area. In this embodiment, the data structure of the volume-file management
 area is compliant with International Standard Organization (ISO) 9660. The
 ISO 9660 is adopted in CD-ROM (Compact Disk-Read Only memory).
 The volume-file management area includes a volume descriptor, a path table
 and a directory record.
 In the volume descriptor, the size of the volume space and information on
 recording location of the path table, information on recording location of
 the directory record, information on disk production date or the like are
 recorded. In the path table, a table which allows paths of all directories
 existing on the information recording medium to correspond to the
 recording location information is recorded. In the directory record,
 information on an identifier of each director or file (generally a
 directory title or a file title), information on recording location of
 data, the size of the file, properties or the like are recorded.
 Portion (d) of FIG. 10 shows a further detailed data structure of the
 directory record. In a directory record for a root directory, a property
 and an identifier of the root directory, a production date or the like are
 recorded. Furthermore, in the directory record for the root directory
 (first sector), information on recording location of the directory is
 recorded. In the directory record for the root directory (second sector),
 similar information is recorded. In addition, in a directory record for
 file A, information on recording location of data of file A, a data
 length, information on the identifier for the file, a copyright managing
 identifier or the like are recorded. Thus, the plurality of directories
 form a hierarchy. The root directory is a directory located on the top of
 the hierarchy. This will be described in detail with reference to the
 accompanying drawings later.
 In the data recording area, a file which is scrambled and a file which is
 not scrambled are recorded. For example, scrambled files A and C are
 scrambled files, and non-scrambled file B is a file which is not
 scrambled. It is preferable that a file storing AV data whose copyright
 should be protected is a scrambled file.
 Portion (e) of FIG. 10 shows a data structure of the scrambled file A. The
 file A is partitioned into a plurality of continuous sectors starting from
 a sector n. Data stored in each of the plurality of sectors is subjected
 to scramble-processing. Hereinafter, in this specification, the sector
 storing data having been subjected to the scramble-processing is referred
 to as "a scrambled sector".
 Portion (f) of FIG. 10 shows a data structure of the non-scrambled file B.
 The file B is partitioned into a plurality of continuous sectors starting
 from a sector m. Data stored in each of the plurality of sectors is not
 subjected to the scramble-processing. Hereinafter, in this specification,
 the sector storing data not subjected to the scramble-processing is
 referred to as "a non-scrambled sector".
 Portions (a) to (c) of FIG. 11 show a data structure of the directory
 record in the volume-file management area. The directory record includes a
 directory record length, file recording location information, a file data
 length, a file identifier and copyright managing information.
 The directory record length is information showing the size of the
 directory record of the file (or directory). The file recording location
 information is information showing a location from which the sector having
 data of the file recorded (hereinafter, referred to as an extent) starts.
 The file data length is information showing the number of sectors
 constituting the file. The file identifier is identification information
 for identifying the file (file title). The copyright managing information
 is information regarding the copyright management of the file.
 The copyright managing information includes a scramble flag field and a
 scramble system field. In the scramble flag field is recorded a flag for
 indicating whether or not data in the file has been subjected to the
 scramble-processing. In the case where data in the file has been subjected
 to the scramble-processing, a flag having value 1 is recorded in the
 scramble flag field. In the case where data in the file has not been
 subjected to the scramble-processing, a flag having value 0 is recorded in
 the scramble flag field. Therefore, by referring to the scramble flag
 field, it can be determined whether or not the data in the file has been
 subjected to the scramble-processing. In the scramble system field is
 recorded an identifier for indicating a system of the scramble-processing
 which has been performed to the data in the file. Therefore, by referring
 to the scramble system field, the scramble-processing which has been
 performed to the data can be determined in a unit of file.
 Hereinafter, referring to portions (d) to (f) of FIG. 11, an exemplary
 scramble system will be described. A scramble system identifier
 corresponding to this scramble system is set as 1.
 Portion (d) of FIG. 11 shows a data structure of a scramble information
 sector recorded in a control data area in a lead-in area. The scramble
 information sector includes a sector header field and a main data field. A
 "sector header field" is a field where control information used by a
 reproduction apparatus is recorded, and it is difficult to directly read
 the field by an external unit, such as a PC.
 The sector header field of the scramble information sector includes an
 address field where an identifier for the information reproducing device
 to identify the sector is recorded, a scramble system field where
 information for specifying the scramble system performed to the
 information recording area (as described above, the scramble system of
 this example is set as 1) is recorded, and a mutual authentication key
 field where a mutual authentication key for use in authentication
 processing for determining whether or not the information reproducing
 device should supply data subjected to copyright protection to an
 apparatus requiring transfer of reproduction data (hereinafter, referred
 to as mutual authentication processing). The mutual authentication
 processing will be described in detail later.
 In the main data field of the scramble information sector is recorded a
 table for determining a random number sequence to be used at the time of
 scramble-processing from a key for scrambling. Therefore, it is not until
 the information reproducing device uses the table recorded in the scramble
 information sector and the key for the scrambling that
 descramble-processing can be performed. Hereinafter, the initial value for
 determining the random number sequence is referred to as preset data.
 Portion (e) of FIG. 11 shows a data structure of a scrambled sector in the
 data recording area. The sector header field in the scrambled sector
 includes an address field, a scramble flag field where a flag for
 identifying whether or not the scramble-processing has been performed to
 the main data field in the sector, a seed key field where the key used at
 the time of scrambling (hereinafter, referred to as a seed key) is
 recorded, and a use identifying information field where information for
 identifying use of the file is recorded. In the scramble flag field is
 recorded value 1 indicating that scramble-processing has been performed.
 In the seed key field is recorded a key to be used for
 descramble-processing for the main data field. Furthermore, in the use
 identifying information field is recorded information on the use of the
 recorded data such as industrial use or consumer use, and is recorded
 information indicating a reproduction restriction in the case where the
 use of the information reproducing device is different from the use
 identifying information. Furthermore, in the main data field is recorded
 data having been subjected to the scramble-processing determined by a
 scramble system specified by the scramble information sector in the
 lead-in area and the seed key in the sector header field in the scrambled
 sector. More specifically, a preset data is determined based on the value
 recorded in the seed key field and referring to the table in the scramble
 information sector. Then, by using the random number sequence determined
 by the preset data, scrambled/descramble-processing is possible. In the
 following description, the seed key is the same for every file.
 On the other hand, the sector header in the non-scrambled sector includes
 an address field and a scramble flag field. In the scramble flag field is
 recorded a value 0 indicating that the scramble-processing has not been
 performed to the main data field in the sector. Therefore, the information
 reproducing device can easily recognize that it is unnecessary to perform
 descramble-processing by detecting the value 0 in the scramble flag field.
 Next, referring to FIG. 12, an exemplary scramble system will be described.
 Portion (a) of FIG. 12 shows that, by performing a logical operation of
 data sequence D.sub.j (j is an integer from 0 to 2047) of 8 bits and a
 random number sequence S.sub.j of 8 bits generated based on a certain
 initial value, scrambled data SD.sub.j is obtained. More specifically, a
 preset data of 15 bits determined by the scramble information sector
 recorded in the lead-in area and the seed key in the sector header field
 in each sector is set in a shift register 301, and an exclusive OR of the
 most significant bits r.sub.14 and r.sub.10 is put to the bit 0 while
 shifting to the direction of most significant bits. Thus, the random
 number sequence S.sub.j is generated. Herein, the bit in the bit location
 r.sub.0 is input to a logical operation block 302 for every one bit shift,
 and a value of 8 bits input to the logical operation block 302 for eight
 shifts is set as S.sub.j. By the logical operation (e.g., exclusive OR or
 the like) of S.sub.j obtained in this manner and recorded data of 8 bits,
 data SD.sub.j after scrambling is obtained. When the size of the main data
 in one sector is 2048 bytes, scramble-processing in one sector can be
 performed by repeating the aforementioned procedure 2048 times from
 SD.sub.0 to SD.sub.2047.
 Furthermore, portions (b) and (c) of FIG. 12 show conversion from the
 scramble information sector to a table for determining preset data. In the
 scramble information sector shown in portion (b) of FIG. 12, four entries
 of the table are recorded, and each entry consists of a set of a seed key
 and preset data. These sets are tabled to obtain the table shown in
 portion (c) of FIG. 12. For example, when the seed key recorded in the
 sector header is 01b (b means binary number), 0077h (h means hexadecimal
 number) as preset data is set in the shift register 301 in portion (a) of
 FIG. 12 as the initial value, and the aforementioned shift operation and
 the logical operation are performed. Thus, scramble/descramble-processing
 becomes possible.
 As described above, the information recording medium in this embodiment
 enables scrambling in a file unit. The information recording medium in
 this embodiment has information whether or not scrambling has been
 performed as copyright managing information in the file management area
 and in the scramble flag field in the sector header in a unit of sector.
 This enables a device such as a personal computer which only recognizes
 main data to recognize whether or not scramble-processing has been
 performed, and enables a device such as an optical disk drive which cannot
 recognize main data to recognize whether or not scramble-processing has
 been performed. Therefore, in the case where data is to be reproduced by
 the optical disk drive connected to the personal computer, it is possible
 for both of the former and the latter to determine whether or not the
 copyright of the data should be protected.
 Furthermore, since in the information recording medium of this embodiment,
 different scramble-processing for every file can be performed by changing
 the seed key, even if a scramble method for one scrambled file is
 decrypted by an illegal act, another scrambled file can be prevented from
 being descrambled by the decrypted scramble system. Thus, it is possible
 to enhance security in processing for copyright protection.
 Furthermore, in the case where the information recording medium of this
 embodiment is used for the purpose of copyright protection, the scramble
 information sector where scramble information indispensable to
 descrambling is recorded exists in the lead-in area which cannot be read
 by an apparatus such as a personal computer. For this reason, the act of
 illegally reading the scramble information can advantageously be
 prevented. Furthermore, since the lead-in area is reproducible by the same
 reproducing means as the data recording area, there is no need for
 providing a special reproducing means.
 Furthermore, since information recorded in a sector such as seed key,
 scramble flag, use identifying information or the like are recorded in the
 sector header field and cannot be read by an apparatus such as a personal
 computer, (as in the case of recording the scramble information in the
 lead-in area described above), the act of illegally reading the
 information can advantageously be prevented.
 Furthermore, since the use identifying information is recorded in the
 sector header field, it is possible to determine depending on the content
 of the recorded data whether the reproducing device should perform
 reproduction or prohibit reproduction. Therefore, for example, by
 recording different identifiers between an industrial disk and a consumer
 disk in this area, the industrial disk can be prevented from being
 reproduced by a consumer reproducing device.
 Furthermore, by recording a mutual authentication key for use in mutual
 authentication processing, the reproducing device can change data received
 and transmitted at the mutual authentication operation for every mutual
 authentication key. Thus, the processing method for the mutual
 authentication processing can be advantageously prevented from being
 illegally decrypted. Therefore, it is possible to prevent the act of
 illegally copying to a magnetic disk drive or the like.
 In this embodiment, the volume-file structure is based on ISO9660, which is
 the international standard, but it is not limited thereto, and another
 volume-file structure can be used, as long as the volume-file structure
 has the information described above.
 In this embodiment, the scramble system uses the logical operation of
 random numbers and data, but it is not limited thereto, and another
 scramble system can be used, as long as the scramble system has a table
 and a seed key for referring to the table.
 In this embodiment, a table for determining preset data is recorded in the
 lead-in area, but it is not limited thereto, and another parameter can be
 used, as long as the parameter can determine the table. An identifier for
 specifying one table among a plurality of previously known tables can be
 recorded.
 In this embodiment, an information recording area for identifying the use
 as the use identifying information field is provided in the sector header
 field in the scrambled sector. However, it is not necessary that the field
 is definitely isolated, but the use can be classified by a value of the
 seed key.
 In this embodiment, in the scrambled sector, all 2048 bytes in the main
 data field are subjected to the scramble-processing. However, the
 scramble-processing is not necessarily performed to the entire main data
 field, but can be performed to a predetermined part of the field.
 (Fourth Embodiment)
 Next, another data structure of the information recording medium according
 to the present invention will be described. The data structure of the
 information recording medium is the same as the information recording
 medium shown in FIG. 10. Hereinafter, only the different points from the
 data structure shown in FIG. 10 will be described.
 Portions (a) to (c) of FIG. 13 show a data structure of a directory record
 recorded in the volume-file management area. In the scramble system field
 in the copyright managing information of the directory record is recorded
 a value 2 indicating a scramble system which will be described in this
 embodiment.
 Portion (e) of FIG. 13 shows a data structure of the scrambled sector. The
 sector header field in the scrambled sector includes an address field, a
 scramble flag field, a media CGMS (Copy Generation Management System) data
 field, an encrypted original CGMS data field, an encrypted title key field
 and an encrypted use identifying information field.
 In the scramble flag field is recorded a value 1 indicating that the
 scramble-processing has been performed.
 In the media CGMS data field is recorded copy permission information of the
 information recording medium. In the encrypting original CGMS data field
 is recorded copy permission information of most original data, in the case
 where data of this sector is copied from another medium. Herein, the media
 CGMS data represents copy permission information of the data of the
 information recording medium. The media CGMS data is updated at the time
 of a copy operation. The original CGMS data represents copy permission
 information at the time of disk production. Since the original CGMS data
 is encrypted, it is copied as it is at the time of a copy operation. Table
 1 shows the definition of the media CGMS data and the original CGMS data.
 TABLE 1
 Media CGMS data/
 Original CGMS data Content
 00b Copying permitted
 01b Unused
 10b One copying permitted
 11b Copying prohibited
 Referring to Table 1, for example, when the media CGMS data is 11b and the
 original CGMS data is 10b, it should be determined that the data in the
 sector is originally in the state where only one copy is permitted (media
 CGMS data and original CGMS data are both 01b), and the media CGMS data is
 changed to 11b which means copying prohibition by having already conducted
 one copy operation. Hereinafter, the media CGMS data and the original CGMS
 data in combination are referred to as CGMS control information.
 In the encrypted title key field is recorded a key for descrambling the
 scramble-processing performed to the main data field.
 In the encrypted use identifying information field is recorded
 identification information for specifying the use. The encrypted original
 CGMS data field, the encrypted title key field and the encrypted uses
 identification information field are all subjected to encrypting
 processing, and information cannot be read simply by reading the sector
 header field. The encrypted data has been encrypted using an encrypted
 disk key recorded in the sector header field in the lead-in area of the
 information recording medium. Therefore, in order to decrypt the encrypted
 information in the scramble information sector header field, the encrypted
 disk key is required.
 Portion (d) of FIG. 13 shows a data structure of the scramble information
 sector. In the following description, in order to definitely differentiate
 encrypted data and data whose code is decrypted, the encrypted data is
 denominated with "encrypted", and the data whose code is decrypted is
 denominated with "decrypted". For example, data obtained by encrypting the
 title key is referred to as an "encrypted title key", and data obtained by
 decrypting the encrypted title key is referred to as a "decrypted title
 key".
 The scramble information sector is recorded in the control data area in the
 lead-in area.
 In the sector header field in the scramble information sector is recorded a
 value 2 indicating that the scramble system is this type of scramble
 system. Furthermore, in the mutual authentication key field is recorded an
 mutual authentication key for use in mutual authentication processing for
 determining whether or not data after descrambling is to be supplied. This
 mutual authentication key will be described in detail later in an
 embodiment of an information reproducing device.
 In the main data field in the scramble information sector is recorded an
 encrypted original CGMS data, an encrypted title key, and an encrypted
 disk key for decrypting an encrypted use identifying information of the
 scrambled sector. The encrypted disk key is further encrypted, and the key
 for decrypting the encrypted disk key (hereinafter, referred to as a
 master key) is provided by the information reproducing device.
 In the main data field in the scramble information sector is recorded a
 plurality of encrypted disk keys such as encrypted disk key 1, encrypted
 disk key 2, etc. The encrypted disk key is encrypted by a corresponding
 master key in such a manner that the encrypted disk key 1, the encrypted
 disk key 2, etc. are encrypted by the master key 1, the master key 2, etc.
 respectively. Herein, the encrypted disk key 1, the encrypted disk key 2,
 etc. are obtained by encrypting the same disk key information by different
 master keys. Therefore, in the case where an information reproducing
 device A internally includes the master key 1 and another information
 reproducing device B internally includes the master key 2, the information
 reproducing device A decrypts the encrypted disk key 1 and the information
 reproducing device B decrypts the encrypted disk key 2, thus obtaining a
 decrypted disk key having the same content.
 Portion (f) of FIG. 13 shows a data structure of the non-scrambled sector.
 In the scrambled sector flag field is recorded a value 0. The data
 recorded in the main data field is not subjected to scramble-processing.
 This indicates that the same data access as a conventional information
 recording disk is possible.
 As described above, in the information recording medium in this embodiment,
 data reproduction is possible by exactly the same access as the
 conventional device for reproduction of the non-scrambled sector. On the
 other hand, in order to perform reproduction of the scrambled sector, the
 information reproducing device having the master key reads the scramble
 information sector in the lead-in area and decrypts the encrypted disk key
 by the master key, and further decrypts the encrypted title key of the
 sector header in the scrambled sector using the decrypted disk key, and
 performs descramble-processing of the scrambled data using the decrypted
 title key. Thus, data can be reproduced.
 Hereinafter, the case where the scramble system described in the third
 embodiment is used as an example of the scramble system will be described.
 In the third embodiment, preset data is generated by using a conversion
 table. In the information recording medium in this embodiment, when an
 initial value for random number generation is encrypted and recorded in
 the encrypted title key field, scramble-processing of data can be easily
 performed by using the shift register 301 and the logical operation block
 302 in portion (a) of FIG. 12. More specifically, the decrypted title key
 is used as an initial value of the shift register 302, and the shift is
 repeated so that a random number sequence S.sub.j is generated. Then, the
 logical operation of the random number sequence S.sub.j and the data
 sequence D.sub.j is performed, so that scramble-processing can be
 performed. Furthermore, descrambling of data can also be performed by
 using the shift register 301 in portion (a) of FIG. 12.
 As described above, the information recording medium in this embodiment
 enables scrambling in a file unit. In addition, the information recording
 medium in this embodiment has information whether or not scrambling is
 performed as copyright managing information in the file management area
 and in the scramble flag field in the sector header in a unit of sector.
 This enables a device such as a personal computer which only recognizes
 main data to recognize whether or not scramble-processing is performed,
 and enables a device such as an optical disk drive which cannot recognize
 main data to recognize whether or not scramble-processing is performed.
 Therefore, in the case where data is to be reproduced by the optical disk
 drive connected to the personal computer, both of the former and the
 latter can determine whether or not the copyright of the data should be
 protected.
 Furthermore, since in the information recording medium of this embodiment,
 different scramble-processing for every file can be performed by changing
 the title key, even if a scramble method for one scrambled file is
 decrypted by an illegal act, another scrambled file can be prevented from
 being descrambled by the decrypted scramble system. Thus, it is possible
 to enhance security in processing for copyright protection.
 Furthermore, in the case where the information recording medium of this
 embodiment is used for the purpose of copyright protection, the scramble
 information sector where scramble information indispensable to
 descrambling is recorded exists in the lead-in area which cannot be read
 by an apparatus such as a personal computer. For this reason, the act of
 illegally reading the scramble information can advantageously be
 prevented. Furthermore, since the lead-in area is reproducible by the same
 reproducing means as the data recording area, there is no need for
 providing a special reproducing means.
 Furthermore, since the scramble flag, the CGMS control information, the
 encrypted title key and the encrypted use identifying information, which
 are recorded in a unit of sector, are recorded in the sector header field
 which cannot be read by an apparatus such as a personal computer, as in
 the case of recording the scramble information in the lead-in area
 described above, the act of illegally reading the information can
 advantageously be prevented.
 Furthermore, since the use identifying information is recorded in the
 sector header field, it is possible to determine depending on the content
 of the recorded data whether the reproducing device should perform
 reproduction or prohibit reproduction. Therefore, for example, by
 recording different identifiers between an industrial disk and a consumer
 disk in this area, the industrial disk can be prevented from being
 reproduced by a consumer reproducing device.
 Furthermore, by recording a mutual authentication key for use in mutual
 authentication processing, the reproducing device can change data received
 and transmitted at the mutual authentication operation for every mutual
 authentication key. Thus, the processing method for the mutual
 authentication processing can be advantageously prevented from being
 illegally decrypted. Therefore, it is possible to prevent the act of
 illegally copying to a magnetic disk drive or the like.
 Furthermore, in the information recording medium in this embodiment, a
 hierarchical encrypting/scramble-processing is performed in such a manner
 that the main data in the scrambled sector is encrypted by the title key,
 the title key is encrypted by the disk key, and the disk key is encrypted
 by the master key. For this reason, even if the main data in the scrambled
 sector is illegally copied, descrambling can be prevented, so that the
 illegal copying makes no sense.
 Furthermore, since the CGMS control information is recorded, even if a file
 is copied from the information recording medium in this embodiment to
 another rewritable medium, it is possible to determine whether copying was
 illegal or legal.
 In this embodiment, the scramble-processing is performed by the logical
 operation of data and the random number obtained by using the title key as
 the initial value. However, the scramble system is not limited thereto,
 but another scramble system can be used, as long as the system scrambles
 data in accordance with a specified key.
 In this embodiment, the volume-file structure is based on ISO9660, which is
 the international standard, but it is not limited thereto, and another
 volume-file structure can be used, as long as the copyright managing
 information equivalent to the content described in this embodiment can be
 recorded in the volume-file structure.
 In this embodiment, in the scrambled sector, all data in the sector is
 scrambled. However, the entire main data in the sector is not necessarily
 scrambled, but a part of the main data can be scrambled.
 In this embodiment, in the scrambled file, all sectors constituting the
 file are subjected to the scramble-processing. However, a part of sector
 in the scrambled file can be subjected to the scramble-processing.
 In this embodiment, the CGMS control information uses three types, i.e.,
 one copying permitted, copying prohibition, and copying permitted, but
 information on two copies permitted, three copies permitted or the like
 can be recorded by extending allocated bits.
 The scramble method of the main data described in this embodiment is only
 an example, and the scramble method is not limited thereto. Another method
 can be used, as long as scramble-processing is performed based on certain
 key information (title key in this embodiment).
 (Fifth Embodiment)
 Hereinafter, an information reproducing device for reproducing the
 information recording medium according to the present invention will be
 described with reference to the accompanying drawings. The information
 reproducing device is a device which can commonly reproduce the third and
 fourth embodiments of the information recording mediums, unless mentioned
 otherwise. Therefore, although an operation for reproducing the fourth
 embodiment of the information recording medium will be described below as
 an example, the third embodiment of the information recording medium can
 be processed in the same manner by substituting the seed key field for the
 encrypted title disk key, and substituting the preset data conversion
 table for the encrypted disk key of the scramble information sector.
 FIG. 14 is a block diagram showing an information reproducing device 500
 according to the present invention. The information reproducing device 500
 includes a main processor 501, a bus interface circuit 503, a main memory
 504, a SCSI (Small Computer System Interface) control card 506 for
 controlling a protocol determined by an SCSI, an AV decoder card 507 for
 extending compressed digital AV data to convert into an analog AV data and
 output the analog AV data, an optical disk drive 509 for reproducing the
 information recording medium of the present invention, and a hard disk
 drive 510.
 The main processor 501, the bus interface circuit 503 and the main memory
 504 are interconnected via the processor bus 502. The bus interface
 circuit 503, the SCSI control card 506 and the AV decoder card 507 are
 interconnected via a system bus 505. The SCSI control card 506, the
 optical disk drive 509 and the hard disk drive 510 are interconnected via
 a SCSI bus.
 Next, a reproduction operation of an AV file by the information reproducing
 device 500 will be described.
 When an optical disk is mounted on the optical disk drive 509, the main
 processor 501 reads a volume-file management area in the optical disk via
 the SCSI control card 506, and the main memory 504 stores the volume-file
 management area (hereinafter, data in the stored volume-file management
 area is referred to as file managing information).
 The main processor 501 performs processing where the AV decoder card 507
 and the optical disk drive 509 determine therebetween whether or not the
 other component has a copyright protection function (hereinafter, referred
 to as mutual authentication processing). During this processing, in the
 case where either one of the two components detects an error, the mutual
 authentication processing is regarded as having failed, and subsequent
 procedure is cancelled. On the other hand, in the case where the mutual
 authentication processing is normally ended, the optical disk drive 509
 transmits the encrypted disk key of the mounted disk to the AV decoder
 card 507. At this time, the optical disk drive 509 further supplies an
 encrypted disk key obtained by encrypting based on a key generated during
 the mutual authentication processing (hereinafter, referred to as a bus
 key) at the time of outputting the encrypted disk key. The AV decoder card
 507 internally retains the received encrypted disk key after decrypting it
 with the bus key.
 Thereafter, in the case where a file recorded in the optical disk is to be
 reproduced, the main processor 501 refers to a scramble flag of copyright
 managing information in the file managing information previously stored in
 the main memory 504, and determines whether or not the file to be
 reproduced is a scrambled file. As a result of the determination, when it
 is determined that the file to be reproduced is an unscrambled file, the
 optical disk drive 509 receives a reproduction instruction from the main
 processor 501 via the SCSI control card 506, and transfers non-scrambled
 data. On the other hand, if the main processor 501 determines based on the
 scramble flag of the file managing information that the file to be
 reproduced is a scrambled file, the mutual authentication processing
 between the optical disk drive 509 and the AV decoder card 507 is
 executed.
 When the main processor 501 detects an error during the mutual
 authentication processing, the processing is cancelled without performing
 reproduction processing. On the other hand, in the case where the mutual
 authentication processing is normally ended, the optical disk drive 509
 transmits back the encrypted title key, prior to reproduction of data, and
 the encrypted title key is transferred to the AV decoder card 507 by the
 main processor 501. At this time, the optical disk drive 509 transfers the
 encrypted title key which is encrypted by the bus key previously retained.
 Furthermore, the AV decoder card 507 internally stores the received
 encrypted title key after decrypting it by the bus key.
 Thereafter, the optical disk drive 509 supplies scrambled data read from
 the mounted disk, and the microprocessor 501 transfers the scrambled data
 to the AV decoder card 507. The AV decoder card 507 descrambles the
 scrambled data using the title key already stored therein, and converts it
 to analog AV data to output an analog signal from a video output and an
 audio output. As described above, the information reproducing device 500
 can reproduce the information recording medium of the present invention.
 As for a copy operation of a scrambled file from the optical disk drive 509
 to the hard disk drive 510, since the hard disk drive 510 cannot execute
 the mutual authentication processing, the mutual authentication is put to
 an error end. Therefore, the processing is cancelled before the optical
 disk drive 509 supplies data to the SCSI bus, and thus the copy operation
 is not executed.
 Furthermore, if a program for illegally copying a scrambled file read by
 the optical disk drive 509 to the hard disk drive 510 is loaded to the
 main memory 504, the mutual authentication processing is normally ended in
 a certain form, and then the transferred scrambled data is copied in the
 hard disk drive 510, the scrambled data is copied in the hard disk drive
 510. However, the mutual authentication processing between the hard disk
 drive 510 and the AV decoder card 507 is required once again, in order to
 reproduce data copied in the hard disk drive 510. In this case, since the
 hard disk drive 510 does not have means for generating a bus key, it is
 impossible that the scrambled file on the hard disk drive 510 is
 reproduced by the AV decoder card 507.
 Therefore, even if illegal copying is made, the copy operation can make no
 sense. As a result, a copyright protection mechanism can be realized.
 Hereinafter, further detailed structures and operations of the optical disk
 drive 509 and the AV decoder card 507, which are components of the
 information reproducing device 500, will be described with reference to
 FIGS. 15 and 16, respectively.
 FIG. 15 is a block diagram showing the structure of the optical disk drive
 509. The structure thereof will be described below. Reference numeral 600
 denotes an SCSI control circuit. Reference numeral 601 denotes a decoder
 authentication circuit for performing a mutual authentication processing
 with an AV decoder. Reference numeral 602 denotes a microcontroller for
 controlling the entire optical disk drive. Reference numeral 603 denotes a
 program ROM storing an operation program of the microcontroller. Reference
 numeral 604 denotes a control bus for transmitting control data. Reference
 numeral 605 denotes an ECC (Error Correction Code) processing memory used
 at the time of error correction processing for correction a readout error
 at the time of reproducing data. Reference numeral 606 denotes a data
 reproducing circuit for reading data from the optical disk 607,
 digitalizing, demodulation, error correction processing or the like.
 Reference numeral 607 denotes an information recording medium of the
 present invention and an optical disk having the data structure shown in
 the third embodiment and the fourth embodiment.
 Next, the operation of the optical disk drive 509 at the time of mutual
 authentication processing and at the time of reproducing data will be
 described.
 The optical disk drive 509 which received a mutual authentication request
 by the SCSI control circuit 600 controls the decoder authentication
 circuit 601 so as to execute a predetermined mutual authentication
 processing. Since the protocol will be described in detail later, it is
 omitted here. In the protocol for the mutual authentication processing, in
 the case where the microcontroller 602 detects some error, the SCSI
 control circuit 600 reports an error and the mutual authentication
 processing and a subsequent key information transfer operation are
 cancelled. In the case the mutual authentication processing is normally
 ended, a bus key which is determined at the mutual authentication
 processing is stored in the decoder authentication circuit 601.
 In the mutual authentication processing at the time of disk replacement and
 reset, following the mutual authentication processing, a read request of
 an encrypted disk key is issued to the optical disk drive 509. At this
 time, the optical disk drive 509 controls the data reproducing circuit
 606, so as to read an encrypted disk key information from the optical disk
 607, and further supplies an encrypted disk key encrypted using the bus
 key already retained in the decoder authentication circuit 601 out from
 the SCSI control circuit 600. On the other hand, in the case of the mutual
 authentication processing at the time of reproducing a scrambled file,
 following a normal end of the mutual processing, the optical disk drive
 509 receives a readout information of an encrypted title key. At this
 time, the optical disk drive 509 controls the data reproducing circuit 606
 so as to read an encrypted title key information from the optical disk
 607, and data having been encrypted using the bus key already retained in
 the decoder authentication circuit 601 is supplied out from the SCSI
 control circuit 600.
 In response to a reproduction request of a file data issued thereafter, the
 optical disk drive 509 supplies out scrambled data read from the optical
 disk 607 from the SCSI control circuit 600. This is the end of the
 description of the optical disk drive 509.
 Although the optical disk drive 509 in this embodiment receives a transfer
 request of an encrypted disk key, and then reproduces an encrypted disk
 key field of the optical disk 607, the optical disk drive 509 can read it
 at the time of mounting the optical disk 607, and internally retains it.
 Next, the structure and the operation of the AV decoder card will be
 described with reference to FIG. 16.
 FIG. 16 is a block diagram showing the structure of the AV decoder card
 507. The components thereof will be described below. Reference numeral 700
 denotes a system interface circuit for controlling reception and
 transmission of information with a system bus. Reference numeral 701
 denotes a drive authentication circuit for performing mutual
 authentication processing with the optical disk drive 509. Reference
 numeral 702 denotes a microcontroller for controlling the entire AV
 decoder card 507. Reference numeral 703 denotes a program ROM where an
 operation program of the microcontroller 702 is stored. Reference numeral
 704 denotes a control bus for transmitting control information. Reference
 numeral 705 denotes a descramble circuit for descrambling scrambled data.
 Reference numeral 706 denotes an audio/video decoder circuit for extending
 compressed AV digital data and converting it to an analog AV data.
 Reference numeral 707 denotes an audio/video decoding memory, an operating
 memory, which the audio/video decoder circuit 706 uses for data
 conversion.
 Next, the operation of the AV decoder card 507 at the time of mutual
 authentication processing and scrambled file reproduction will be
 described.
 First, at the time of mutual authentication processing at the time of reset
 and media replacement, the microcontroller 702 controls the drive
 authentication circuit 701 so as to execute mutual authentication
 processing with the optical disk drive 509 in accordance with a
 predetermined protocol. In the case where the drive authentication circuit
 701 detects an error at the time of mutual authentication processing, the
 error is reported via the system interface circuit 700, and the processing
 is cancelled. On the other hand, in the case where the mutual
 authentication processing is normally ended, the drive authentication
 circuit 701 internally retains a bus key determined in the mutual
 authentication processing.
 Furthermore, the AV decoder card 507 receives an encrypted disk key from
 the system interface circuit 700. Since the received encrypted disk key
 has been encrypted with the bus key in the optical disk drive 509, the AV
 decoder card 507 decrypts the encrypted disk key with the bus key already
 retained in the drive authentication circuit 701, and then transfers it to
 the descramble circuit 705. The descramble circuit 705 internally stores
 the received encrypted disk key.
 On the other hand, at the time of reproducing a scrambled file, prior to
 the reproduction of the file, the mutual authentication processing with
 the optical disk drive 509 is executed once again. Here, again, in the
 case where an error occurs in the mutual authentication processing, the
 mutual authentication processing and the subsequent file reproduction
 operation are cancelled. In the case where the mutual authentication
 processing is normally ended without any error, the AV decoder card 507
 receives an encrypted title key via the system interface circuit 700.
 Since the encrypted title key has been further encrypted with the bus key
 in the optical disk drive 509, the encrypted title key is decrypted with
 the bus key retained in the drive authentication circuit 701, and
 transfers the result to the descramble circuit 705. The descramble circuit
 705 internally stores the received encrypted title key.
 Thereafter, scrambled data of the scrambled file received from the system
 interface circuit 700 is transferred to the descramble circuit 705 as it
 is, and is subjected to descramble-processing based on the title key
 already retained and transferred to the audio/video decoder circuit 706 so
 as to be converted to an analog AV signal and output.
 As described above, according to the information reproducing device 500 of
 this embodiment, the optical disk drive 509 includes the decoder
 authentication circuit 601, and the AV decoder card 507 includes the drive
 authentication circuit 701. For this reason, key information is not
 supplied to an apparatus which has an objective of illegally copying a
 file. Thus, even if data of a scrambled file is illegally copied, copied
 data makes no sense by not supplying the key information for executing
 descrambling. Therefore, an effect of protecting copyright of the file is
 provided.
 According to the information reproducing device of this embodiment, since
 the AV decoder card 507 internally has the descramble circuit 705 for
 performing descramble-processing depending on the key information, it is
 possible to descramble the scrambled data for reproduction.
 In this embodiment, an SCSI bus is used for the bus connected to the
 optical disk drive 509. However, the bus is not limited thereto, and a bus
 compliant with ATAPI (AT Attachment Packet Interface) or IEEE 1394
 (Institute of Electrical and Electronics Engineers 1394) can be used, as
 long as reproduction data can be transferred in accordance with a
 predetermined protocol.
 In this embodiment, the function of the decoder authentication circuit 601
 and the function of the drive authentication circuit 701 can be realized
 by a software executed by the microcontrollers 602 and 702.
 (Sixth Embodiment)
 Next, an information reproducing device 800 according to the present
 invention will be described.
 FIG. 17 is a block diagram showing the structure of the information
 reproducing device 800 according to the present invention. The structure
 of the information reproducing device 800 is the same as that of the
 information reproducing device 500 shown in FIG. 14, except that an SCSI
 control circuit for performing communication compliant with the SCSI
 system is incorporated into an AV decoder card 801. Therefore, the same
 components bears the same reference numerals, and the description thereof
 is omitted.
 Next, the operation of the information reproducing device 800 will be
 described.
 Since the SCSI control circuit incorporated AV decoder card 801 internally
 includes the SCSI control circuit, when a scrambled file reproduction
 request of the optical disk drive 509 is issued from the main processor
 501, the mutual authentication processing between the SCSI control circuit
 incorporated AV decoder card 801 and the optical disk drive 509 is
 directly executed. More specifically, the SCSI control circuit
 incorporated AV decoder card 801 issues a command sequence for mutual
 authentication to the optical disk drive 509, the optical disk drive 509
 responds to the command. In this manner, the mutual authentication
 processing is performed.
 Furthermore, likewise in an operation of reproducing data, it is the SCSI
 control circuit incorporated AV decoder card 801 that makes a reproduction
 request to the optical disk drive 509, not the main processor 501.
 Therefore, data read by the optical disk drive 509 is directly input to
 the SCSI control circuit incorporated AV decoder card 801 and converted to
 an analog AV signal and output.
 FIG. 18 is a block diagram showing the structure the SCSI control circuit
 incorporated AV decoder card 801. Hereinafter, only different points from
 the structure of the AV decoder card 507 shown in FIG. 16 will be
 described.
 Reference numeral 900 denotes a SCSI control circuit for controlling
 reception and transmission of data with SCSI bus 508. Reference numeral
 901 denotes a program ROM where a program to be executed by the
 microcontroller is stored.
 When a reproduction request for a scrambled file is input to the system
 interface circuit 700, the microcontroller 702 controls the drive
 authentication circuit 701 and the SCSI control circuit 900 so as to
 execute the mutual authentication processing with the optical disk drive
 509. At this time, in a mutual authentication protocol, a command is
 directly issued from the SCSI control circuit 900 to the optical disk
 drive 509. Furthermore, the microcontroller 702 controls the drive
 authentication circuit 701 in accordance with the mutual authentication
 protocol so as to perform mutual authentication processing. In the case
 where the mutual authentication processing is ended by an error, the
 microcontroller 702 controls the system interface circuit 700 to report
 the error to the main processor 501 so that the processing is ended. On
 the other hand, in the case where the mutual authentication processing is
 normally ended, data of a scrambled file is directly received by the SCSI
 control circuit 900 from the optical disk drive 509, and data descrambled
 by the descramble circuit 705 is converted to an analog AV signal by the
 audio/video decoder circuit 706 and output. Connected to decoder circuit
 706 is audio/video decoding memory 707. By the procedure described above,
 as in the case of the information reproducing device of the fifth
 embodiment, AV data can be reproduced while preventing the copy operation
 which infringes copyright of data recorded in the information recording
 medium of the present invention.
 As described above, according to the information reproducing device 800 of
 this embodiment, in addition to the feature of the information reproducing
 device of the fifth embodiment, since the optical disk drive 509 and the
 SCSI control circuit incorporated AV decoder card 801 directly receive and
 transmit commands and data, security against illegal decrypting a mutual
 authentication system and key information, and the execution of an unjust
 copy operation can be enhanced.
 Although the information recording medium to be reproduced has been
 described using the fourth embodiment of the information recording medium
 according to the present invention, the same processing is possible for
 the third embodiment of the information recording medium according to the
 present invention , as long as the encrypted title key is replaced by the
 seed key, and the encrypted disk key is replaced by conversion table
 information of the scramble information sector.
 In this embodiment, an SCSI bus is used for the bus connected to the
 optical disk drive 509. However, the bus is not limited thereto, and an
 interface such as an ATAPI or an IEEE 1394 can be used, as long as
 reproduction data can be transferred in accordance with a predetermined
 protocol.
 (Seventh Embodiment)
 Next, an information reproducing device 1000 according to the present
 invention will be described.
 FIG. 19 is a block diagram showing the structure of the information
 reproducing device 1000 according to the present invention. The
 information reproducing device 1000 is an optical disk player. The
 components of the information reproducing device 1000 are the same as
 those of the information reproducing device shown in FIG. 14 or the
 information reproducing device shown in FIG. 17, except for a program ROM
 1001. Therefore, the same components bear the same reference numerals, and
 the description thereof is omitted. The description herein is based on the
 fourth embodiment of the information recording medium.
 At the time of the reset or disk insertion in the optical disk player 1000,
 the microcontroller 702 controls the data reproduction circuit 606 by way
 of control bus 1002 and reads a scramble information sector of a lead-in
 area of the optical disk. An encrypted disk key information read from the
 scramble information sector is transferred to the descramble circuit 705
 and internally retained.
 On the other hand, in reproducing a scrambled file recorded in the optical
 disk 607, the microcontroller 702 controls the data reproduction circuit
 606, reads an encrypted title key from a sector header field of the
 scrambled file to be reproduced, and transfers it to the descramble
 circuit 705. The descramble circuit 705 stores the received title key and
 judges use identifying information. As a result of the determination, in
 the case reproduction is prohibited, the descramble circuit 705 reports an
 error to the microcontroller 702. On the other hand, in the case where the
 descramble circuit 705 determines that reproduction is permitted, the data
 reproduction circuit 606 reads data of the scrambled file, and transfers
 the read scrambled data to the descramble circuit 705. The descramble
 circuit 705 descrambles the scrambled data using a disk key and a title
 key previously stored, and transfers the result to the audio/video decoder
 circuit 706. The audio/video decoder circuit 706 converts the received
 data to an analog AV signal and performs audio/video outputs.
 In this manner, the optical disk player 1000 can descramble the scrambled
 data for reproduction. However, the optical disk player 1000 is different
 from the fifth and the sixth embodiments of the information reproducing
 device of the present invention in that it performs video reproduction
 without executing the mutual authentication processing. This is because,
 since reproduced data is directly input to the audio/video decoder circuit
 706 in this embodiment, a copy operation to other rewritable media such as
 a hard disk drive cannot be performed in the middle of the procedure, and
 thus the mutual authentication processing is not required. Therefore, in
 the structure of this embodiment, without the component which executes the
 mutual authentication processing, the copyright protection is possible.
 Furthermore, since the optical disk player 1000 judges use identifying
 information at the time of reproduction, data whose reproduction is
 prohibited for its use can be prevented from being reproduced.
 Hereinafter, the further detailed structures and operations of a decoder
 authentication circuit 601, a drive authentication circuit 701 and a
 descramble circuit 705, which are used in the fifth and the sixth
 embodiments of the information reproducing device of the present
 invention, will be described. The structure described below is a structure
 common to the fifth embodiment, sixth embodiment and seventh embodiment.
 First, the structure and the operation of the descramble circuit 705 with
 be described with reference to the accompanying drawing. The descramble
 circuit 705 highly depends on a scramble system, so that the structure in
 the case of reproducing the third embodiment of the information recording
 medium of the present invention is different from that in the case of
 reproducing the fourth embodiments of the information recording medium.
 Therefore, in the following description, the descramble circuit for
 reproducing the third embodiment of the information recording medium of
 the present invention will be described with reference to FIGS. 20 and 21.
 The descramble circuit for reproducing the fourth embodiment of the
 information recording medium of the present invention will be described
 with reference to FIGS. 22 and 23.
 FIG. 20 is a block diagram showing the structure of the descramble circuit
 1106 for reproducing the third embodiment of the information recording
 medium of the present invention. Hereinafter, each component will be
 described. Reference numeral 1100 denotes an I/O control circuit for
 performing communication with the control bus 704. Reference numeral 1101
 denotes a selector for switching a block to which an output is directed
 (hereinafter, referred to as a targeted block for output), depending on
 the content of the input data. Reference numeral 1102 denotes a use
 identifying circuit for determining whether or not reproduction is
 permitted, referring to the use identifying information of a reproduction
 file. Reference numeral 1103 denotes a conversion table memory circuit for
 storing a conversion table to generate preset data for a random number
 generating circuit 1104 from the seed key. Reference numeral 1104 denotes
 the random number generating circuit for generating a random number based
 on preset data output from the conversion table memory circuit 1103.
 Reference numeral 1105 denotes a main data descramble circuit for
 performing descramble-processing by performing a logical operation between
 the random number generated by the random number generating circuit 1104
 and scrambled data input from the selector 1101.
 Next, the operation of the descramble circuit 1106 will be described.
 First, in the case where a scramble information sector recorded in the
 lead-in area is to be read after the mutual authentication processing is
 normally ended, a scramble information sector readout is set to the
 selector 1101 via the I/O control circuit 1100, and the selector 1101 sets
 a targeted block for output to the conversion table memory circuit 1103.
 Read data which is input is supplied to the conversion table memory
 circuit 1103 via the selector 1101, and stored as a conversion table for
 determining preset data which is to be used as an initial value for the
 random number generation.
 On the other hand, at the time of reproducing a scrambled file, mutual
 authentication processing is performed prior to reproduction of data, and
 use identifying information in the sector header field received after
 normal end of the mutual authentication processing is input to the use
 identifying circuit 1102, and the seed key is input to the conversion
 table memory circuit 1103. The use identifying circuit 1102 internally has
 information regarding the use identifying information which is permitted
 to be reproduced, identifies whether or not the reproduction is permitted
 by comparing it with the input use identification information, and reports
 the I/O control circuit 1100 and the main data descramble circuit 1105. On
 the other hand, the conversion table memory circuit 1103 which receives
 the seed key outputs a preset data corresponding to the seed key based on
 the received seed key to the random number generating circuit 1104. The
 random number generating circuit 1104 generates a random number sequence
 based on the received preset data and outputs it to the main data
 descramble circuit 1105. Following the sector header field, when the main
 data of the scrambled sector is to be input, a targeted block for output
 of the selector 1101 is switched to the main data descramble circuit 1105.
 Thereafter, the main data descramble circuit 1105 executes
 descramble-processing by performing a logical operation between the main
 data input from the selector 1101 and the random number sequence input
 from the random number generating circuit 1104, and outputs descrambled
 data to the audio/video decoder circuit 706.
 The operation described above will be explained in greater detail with
 reference to FIG. 21 below.
 FIG. 21 is a flow chart explaining the content of the descramble-processing
 in the descramble circuit 1106, in the case where the third embodiment of
 the information recording medium of the present invention is reproduced.
 Each step will be described below.
 (S1200): A targeted block for output of the selector 1101 is switched to
 the conversion table memory circuit 1103, and a conversion table read from
 the scramble information sector of the lead-in area of the information
 recording medium is stored in the conversion table memory 1103.
 (S1201): A targeted block for output of the selector 1101 is switched to
 the I/O control circuit 1100, and a scramble flag in the sector header
 received prior to reproduction of the scrambled file is transmitted back
 to the microcontroller 702. The microcontroller 702 determines whether or
 not the scramble flag is 1, and transmits back the determined result to
 the I/O control circuit 1100. When it is determined that the scramble flag
 is 1, the procedure goes to step (S1202). When it is determined that the
 scramble flag is 0, the procedure goes to step (S1206) with the function
 of the main data descramble circuit 1105 stopped.
 (S1202): A targeted block for output of the selector 1101 is switched to
 the use identifying circuit 1102, and use identifying information in the
 sector header received prior to reproduction of the scrambled file is
 transferred. The use identifying circuit 1102 determines whether or not
 reproduction of the file is permitted, by comparing the received use
 identifying information with reproduction permission information
 internally retained. When it is determined that reproduction is
 prohibited, the procedure goes to step (S1203). When it is determined that
 reproduction is permitted, the procedure goes to step (S1204).
 (S1203): In the case where it is determined at the above processing step
 (S1202) that reproduction of the file is prohibited, an error is reported
 to the microcontroller 702 via the I/O control circuit 1100 in this step,
 and the processing is ended.
 (S1204): A seed key read from the sector header of the scrambled file to be
 reproduced is input to the conversion table memory circuit 1103, and
 preset data is generated from the seed key and the conversion table and
 output to the random number generating circuit 1104.
 (S1205): A targeted block for output of the selector 1101 is switched to
 the main data descramble circuit 1105, and main data of an input scrambled
 file is transferred to the main data descramble circuit 1105. On the other
 hand, the random number generating circuit 1104 generates a random number
 sequence based on preset data input from the conversion table memory
 circuit 1103 and outputs it to the main data descramble circuit 1105. The
 main data descramble circuit 1105 executes descramble-processing by
 performing a logical operation between the input main data and the random
 number sequence.
 (S1206): The main data descramble circuit 1105 outputs descrambled data at
 the time of executing the descrambling, and outputs data input from the
 selector 1101 as it as when the descramble function is stopped, to the
 audio/video decoder circuit 706.
 As described above, the descramble circuit 1106 includes the use
 identifying circuit, so that it is possible to selectively reproduce a
 file having the use identifying information for which reproduction is
 prohibited and a file having the use identifying information for which
 reproduction is permitted.
 Furthermore, the descramble circuit 1106 internally includes the selector
 for separating a scramble identification flag, so that it is possible to
 separate only a scramble flag so as to determine whether or not to perform
 descrambling.
 Furthermore, since a conversion table for converting to preset data can be
 determined in a unit of disk, and a seed key can be determined in a unit
 of file, it is possible reproduce the information recording medium having
 a scramble system with security so high that reproduction cannot be made
 without both of the two data.
 FIG. 22 is a block diagram showing the structure of the descramble circuit
 1308 for reproducing the fourth embodiment of the information recording
 medium of the present invention. Hereinafter, each component will be
 described. Reference numeral 1300 denotes an I/O control circuit for
 performing communication with the control bus 704. Reference numeral 1301
 denotes a selector for switching a targeted block for output, depending on
 the content of the input data. Reference numeral 1302 denotes a disk key
 decrypting circuit for decrypting an encrypted disk key in the case where
 the encrypted disk key is input. Reference numeral 1303 denotes a master
 key storage section for storing a master key to be used for decrypting the
 encrypted disk key in a hardware manner. Reference numeral 1304 denotes a
 sector header decrypting circuit for receiving a disk key decrypted by the
 disk key decrypting circuit 1302, and decrypting the encrypted section in
 the sector header. Reference numeral 1305 denotes a CGMS checking circuit
 for confirming conformity between an original CGMS data decrypted by the
 sector header decrypting circuit 1304 and media CGMS data input from the
 selector. Reference numeral 1306 denotes a use identifying circuit for
 receiving use identifying information decrypted by the sector header
 decrypting circuit 1304 and determining whether or not reproduction is
 permitted. Reference numeral 1307 denotes a main data scramble circuit for
 descrambling main data input from the selector 1301 based on the title key
 input from the sector header decrypting circuit 1304.
 Hereinafter, the descramble circuit 1308 will be described.
 First, in the case where a scramble information sector recorded in the
 lead-in area is read after the mutual authentication processing is
 normally ended, a targeted block for output of the selector 1301 is set to
 the disk key decrypting circuit 1302 via the I/O control circuit 1300, and
 input read data is input to the disk key decrypting circuit 1302 via the
 selector 1301. The disk key decrypting circuit 1302 decrypts a disk key
 based on the master key input from the master key storage section 1303,
 and the disk key is stored in the disk key decrypting circuit 1302.
 On the other hand, at the time of reproducing a scrambled file, the mutual
 authentication processing is performed prior to reproduction of data. When
 the mutual authentication processing is normally ended, the sector header
 of the scrambled file to be reproduced is input to the selector 1301. The
 selector 1301 selects a targeted block for output thereof for every
 content of the sector header, and outputs a scramble flag to the
 microcontroller 702 via the I/O control circuit 1300, outputs media CGMS
 data to the CGMS checking circuit 1305, and outputs encrypted original
 CGMS data and encrypted use identifying information and encrypted title
 key (hereinafter, referred to as an encrypted sector header in
 combination) to the sector header decrypting circuit 1304. The sector
 header decrypting circuit 1304 receives disk key from the disk key
 decrypting circuit 1302, decrypts the encrypted sector header based on the
 disk key, and outputs the original CGMS data to the CGMS checking circuit
 1305, outputs use identifying information to the use identifying circuit
 1306, and outputs the title key to the main data descramble circuit 1307.
 The CGMS checking circuit 1305 receives media CGMS data input from the
 selector 1301 and the original CGMS input from the sector header
 decrypting circuit 1304, and determines whether or not the value indicates
 that reproduction is permitted. At this time, criteria of the
 determination of the CGMS checking circuit 1305 are shown in (Table 2).
 (The meanings represented by the media CGMS data and the original CGMS
 data are consistent with the explanation of the fourth embodiment of the
 information recording medium of the present invention.)
 TABLE 2
 Medium
 identifica- CGMS deter-
 tion infor- Media CGMS Original mination
 mation data CGMS data information
 1 00 00 1
 (Reproduc- 01/10/11 0
 tion only 01 00/01/10/11 0
 medium) 10 00/01/11 0
 10 1
 11 00/01/10 0
 11 1
 0 00 00 1
 (Rewritable 00/10/11 0
 medium) 01/10 00/01/10/11 0
 11 10 1
 00/01/11 0
 In Table 2, in the case where the CGMS determination information represents
 1, the CGMS checking circuit reports to the main data descramble circuit
 1307 and the microcontroller 702 that reproduction is possible. On the
 other hand, in the case where the CGMS determination information
 represents 0, which is an inappropriate value indicating that illegal
 copying or the like is possibly made, the CGMS checking circuit reports an
 error to the main data descramble circuit 1307 and the microcontroller
 702. For example, in Table 2, in the case where the medium identification
 information is 0 indicating a rewritable medium, the media CGMS data is 11
 showing copy prohibited, and the original CGMS data is 10 showing one
 copying permitted, it is believed that a file which is permitted to be
 copied only once has been already copied once to a rewritable medium, so
 that only the media CGMS data becomes 11, and the file is changed to be
 prohibited from being copied. Therefore, the output is 1 meaning that
 reproduction is permitted. On the other hand, if the file which is
 permitted to be copied once is illegally copied, both of the media CGMS
 data and the original CGMS data become 10 meaning that only one copying is
 permitted. Therefore, the CGMS determination information is 0 meaning that
 reproduction is prohibited. On the other hand, the use identifying circuit
 1306 internally includes use identifying information for which
 reproduction is permitted, and determines whether or not the scrambled
 file is to be used for something whose reproduction is permitted, by
 comparing the information with the use identifying information input from
 the sector header decrypting circuit 1304. In the case of the use
 identifying information for which reproduction is not permitted, an error
 is reported to the microcontroller 702 and the main data descramble
 circuit 1307. In the case where the data of the scrambled file is to be
 reproduced, a targeted block for output of the selector 1301 is switched
 to the main data descramble circuit 1307, and read data which is input is
 transferred to the main data descramble circuit 1307. The main data
 descramble circuit 1307 receives the title key from the sector header
 decrypting circuit 1304 and performs descramble-processing of the
 scrambled data based on the received title key to output to the
 audio/video decoder circuit 706.
 As described above, the descramble circuit 1308 decrypts the encrypted disk
 key and the encrypted title key, performs descramble-processing for the
 main data when the title key indicates that reproduction is permitted, and
 outputs scrambled digital AV data to the audio/video decoder circuit 706.
 Next, the operation of reproduction processing of the scrambled file in the
 descramble circuit 1308 will be described with reference to the flow chart
 shown in FIG. 23. Processing content at each step is shown below.
 (S1400): In the case where the encrypted disk key information in the
 lead-in area is input to the read data, a targeted block for output of the
 selector 1301 is set to the disk key decrypting circuit 1302, and the
 encrypted disk key is transferred to the disk key decrypting circuit 1302.
 The disk key decrypting circuit 1302 receives a master key from the master
 key storage section 1303, and decrypts the encrypted disk key and outputs
 the decrypted disk key to the sector header decrypting circuit 1304.
 (S1401): The selector 1301 separates a scramble flag from the sector header
 of the scrambled file read prior to reproduction, and transfers it to the
 microcontroller 702 via the I/O control circuit 1300. The microcontroller
 702 determines whether or not the scramble flag is 1. When the determined
 result is 1, the procedure goes to step (S1402). When the determined
 result is not 1, the procedure goes to step (S1407).
 (S1402): The selector 1301 separates an encrypted sector header from the
 sector header of the scrambled file read prior to reproduction, and
 transfers it to the sector header decrypting circuit 1304. The sector
 header decrypting circuit 1304 decrypts the received encrypted sector
 header based on a disk key previously received from the disk key
 decrypting circuit 1302, separates it by its content, and outputs original
 CGMS data to the CGMS checking circuit 1305, outputs the use identifying
 information to the use identifying circuit 1306, and outputs the title key
 to the main data descramble circuit 1307.
 (S1403): The CGMS checking circuit 1305 outputs CGMS determination
 information in accordance with Table 2 from medium identifying information
 received from the microcontroller 702, media CMGS data received from the
 selector 1301 and original CGMS data received from the sector header
 decrypting circuit 1304. In Table 2, in the case where CGMS determination
 information is 1, the CGMS checking circuit reports to the I/O control
 circuit 1300 and the main data descramble circuit 1307 that it is a normal
 CGMS control information.
 (S1404): In the case where the CGMS determined result is 0, the CGMS
 checking circuit 1305 reports an error to the I/O control circuit 1300 and
 the main data descramble circuit 1307. In the case where the use
 identifying information indicates that reproduction is prohibited for its
 use, the use identifying circuit 1306 reports an error to the I/O control
 circuit 1300 and the main data descramble circuit 1307. Thus, the
 reproduction processing is ended.
 (S1405): The use identifying circuit 1306 determines the use identifying
 information received from the sector header decrypting circuit 1304, and
 in the case where reproduction is permitted, the use identifying circuit
 1306 reports to the I/O control circuit 1300 and the main data descramble
 circuit 1307 that the file is one whose reproduction is permitted.
 (S1406): When the selector 1301 receives the main data of a scrambled file
 as readout data, the main data descramble circuit 1307 is set as a
 targeted block for output thereof, and the main data is transferred
 thereto. The main data descramble circuit 1307 executes
 descramble-processing of the input main data, based on the title key
 received from the sector header decrypting circuit 1304.
 (S1407): In the case where the main data descramble circuit 1307 has
 executed the descramble-processing, the descrambled main data is output to
 the audio/video decoder circuit 706. In the case where the main data
 descramble circuit 1307 has not executed the descramble-processing, the
 data input from the selector 1301 is output as it is to the audio/video
 decoder circuit 706.
 As described above, the descramble circuit 1308 includes the use
 identifying circuit, so that it is possible to selectively reproduce a
 file having the use identifying information for which reproduction is
 prohibited and a file having the use identifying information for which
 reproduction is permitted.
 Furthermore, the descramble circuit 1308 internally includes the selector
 for separating a scramble identification flag, so that it is possible to
 separate only a scramble flag so as to determine whether or not to perform
 descrambling.
 Furthermore, even for a disk of high security, which is hierarchically
 encrypted/scrambled, such as the fourth embodiment of the information
 recording medium of the present invention, by allowing the disk key
 decrypting circuit, the sector header decrypting circuit, the main data
 descramble circuit to operate in association with each other, the
 procedure can be the same as that when descrambling is not performed.
 Furthermore, the descramble circuit includes the CGMS checking circuit
 1305, so that illegally copied data can be detected, thus making it
 possible to prevent the illegally copied data from being reproduced.
 Furthermore, the descramble circuit has a mechanism which protects
 copyright of the information recording medium recorded a software which
 allows for control the generation of copying, namely, how many times data
 is copied, and permits only a predetermined number of copying operations.
 FIG. 24 is a block diagram showing the detailed structure of the decoder
 authentication circuit 601 in the optical disk drive 509. Hereinafter,
 each component will be described. Reference numeral 1500 denotes an I/O
 control circuit for controlling input and output so as to perform
 communication with the microcontroller 602. Reference numeral 1501 denotes
 a random number generating circuit for generating a random number, based
 on a time variable key input from the I/O control circuit 1500. Reference
 numeral 1502 denotes a function fk(R1) generating circuit for determining
 a function fk by a first input (represented by k in FIG. 24) for
 determining the function, and calculating a function value fk(R1) from the
 second input (represented by R1 in FIG. 24), which is an argument of the
 function fk, and outputting the function value fk(R1). Similarly,
 reference numeral 1503 denotes a function gk(R2) generating and comparing
 circuit for calculating a function value gk(R2) from k and R2 and
 outputting the function value gk(R2), and comparing it with decoder
 response data input from the I/O control circuit 1500. Reference numeral
 1504 denotes a bus key generating circuit for generating a bus key, based
 on two function values output from the function gk(R2) generating and
 comparing circuit 1503 and the function fk(R1) generating circuit 1502.
 Reference numeral 1505 denotes a bus encrypting circuit for encrypting
 data output from the data reproducing circuit 606 in accordance with a bus
 key output from the bus key generating circuit 1504.
 Hereinafter, the operation of the decoder authentication circuit 601 will
 be described.
 At the time of reset and disk replacement for the optical disk drive 509,
 the microcontroller 602 previously sets a mutual authentication key k read
 from the sector header in the scramble information sector in the lead-in
 area of the disk to the function fk(R1) generating circuit 1502 and the
 function gk(R2) generating and comparing circuit 1503 via the I/O control
 circuit 1500.
 The function fk(R1) generating circuit 1502 internally retains the mutual
 authentication key k, and thereafter calculates a function fk(R1) when a
 random number value R1 is input at the time of mutual authentication
 processing, and outputs the function fk(R1) to the bus key generating
 circuit 1504 and the I/O control circuit 1500.
 The bus key generating circuit 1504 internally stores the input function
 fk(R1). Subsequently, in the case where a time variable key for generating
 a random number is input from the microcontroller 602 via the I/O control
 circuit 1500, the random number generating circuit 1501 generates a random
 number R2 based on the time variable key and transmits back it to the I/O
 control circuit 1500, and outputs it to the function gk(R2) generating and
 comparing circuit 1503.
 The function gk(R2) generating and comparing circuit 1503 which has
 received the random number R2 calculates the function value gk(R2) from
 the mutual authentication key k previously retained and the random number
 R2, and internally retains it. Furthermore, the function gk(R2) generating
 and comparing circuit 1503 receives decoder response data from the I/O
 control circuit 1500, and compares it with internally calculated function
 gk(R2). As a result of the comparison, in the case where the value of
 gk(R2) and the decoder response data are not matched, the function gk(R2)
 generating and comparing circuit 1503 reports that an error occurs in the
 mutual authentication processing to the microcontroller 602 via the I/O
 control circuit 1500. In the case where the mutual authentication
 processing fails, the processing following the mutual authentication
 processing such as transfer of the encrypted disk key and the encrypted
 title key or the like are cancelled.
 On the other hand, in the case where the two values, gk(R2) and the decoder
 response data, are matched, it is determined that the mutual
 authentication processing is normally ended, and the function value gk(R2)
 is output to the bus key generating circuit 1504. At this time, only in
 the case where the function values fk(R1) and gk(R2) are normally input,
 the bus key generating circuit 1504 generates a bus key based on the two
 function values fk(R1) and gk(R2), and outputs the bus key to the bus
 encrypting circuit 1505.
 The bus encrypting circuit 1505 receives a control signal for switching
 mode (hereinafter, referred to as a mode control signal) from the
 microcontroller 602 via the I/O control circuit 1500. When the mode is a
 disk key reproduction mode or a title key reproduction mode, the bus
 encrypting circuit 1505 performs a predetermined encrypting to an
 encrypted disk key or an encrypted title key input from the data
 reproducing circuit 606, based on a previously input bus key, and then
 outputs the result to the SCSI control circuit 600.
 On the other hand, after supplying out the encrypted title key, in the case
 where an actual file data is to be supplied out, the mode control signal
 is switched to the data reproduction mode, and the bus encrypting circuit
 1505 outputs the data output from the data reproducing circuit 606 to the
 SCSI control circuit 600 without encrypting.
 As described above, the decoder authentication circuit 601 calculates a
 function value determined by the mutual authentication key in the mutual
 authentication processing, and only in the case where the function value
 is matched with the function value supplied from the decoder, the mutual
 authentication processing is normally ended. Furthermore, in the
 reproduction operation, at the time of transfer of the encrypted disk key
 and the encrypted title key, key information which is further encrypted
 using the bus key generated in the mutual authentication processing is
 supplied out.
 Next, the structure of the operation of the drive authentication circuit
 701 on the AV decoder card 507 and the SCSI control circuit incorporated
 AV decoder card 801 will be described with reference to the accompanying
 drawings.
 FIG. 25 is a block diagram showing the structure of the drive
 authentication circuit 701. Hereinafter, each component will be described.
 Reference numeral 1600 denotes an I/O control circuit for receiving and
 transmitting a control signal from and to the microcontroller 702.
 Reference numeral 1601 denotes a random number generating circuit for
 receiving a time variable key from the I/O control circuit 1600 so as to
 generate a random number R1 and transmitting back it to the I/O control
 circuit 1600 and outputting it to a function fk(R1) generating and
 comparing circuit 1603. Reference numeral 1602 denotes a function gk(R2)
 generating circuit for calculating a function gk(R2) based on a constant k
 input from the function fk(R1) generating and comparing circuit 1603 and
 the random number R2 input from the I/O control circuit 1600. Reference
 numeral 1603 denotes a function fk(R1) generating and comparing circuit
 for calculating a function value fk(R1) with respect to k which is 1 to n,
 based on R1 input from the random number generating circuit 1601 and
 comparing it with drive response data input from the I/O control circuit
 1600. Reference numeral 1604 denotes a bus key generating circuit for
 generating a bus key from a function value output from the function gk(R2)
 generating circuit 1602 and a function value output from the function
 fk(R1) generating and comparing circuit 1603. Reference numeral 1605
 denotes a bus decrypting circuit for decrypting data by a bus key output
 from the bus key generating circuit 1604.
 Next, the operation of the drive authentication circuit 701 will be
 described.
 First, at the start of the mutual authentication processing, the drive
 authentication circuit 701 receives a time variable key for a random
 number generation from the microcontroller 702 via the I/O control circuit
 1600, and the random number is generated by the random number generating
 circuit 1601.
 The random number generating circuit 1601 outputs the generated random
 number R1 to the function fk(R1) generating and comparing circuit 1603 and
 the microcontroller 702. Thereafter, the function fk(R1) generating and
 comparing circuit 1603 receives drive response data from the
 microcontroller 702, and calculates functions f(R1), f2(R2), f3(R3) . . .
 using the random value R1 internally retained as an argument, and obtains
 k which allows the drive response data to be matched with fk(R1). At this
 time, in the case where k which allows matching with the drive response
 data is not obtained despite the calculation for all of the retained
 functions, the function fk(R1) generating and comparing circuit 1603
 transmits back an error to the microcontroller 702 via the I/O control
 circuit 1600 as an authentication result.
 On the other hand, in the case where k which allows the drive response data
 to be matched with fk(R1) is obtained, the function fk(R1) generating and
 comparing circuit 1603 transmits back a normal end to the microcontroller
 702 as an authentication result, and outputs k to the function gk(R2)
 generating circuit 1602 and outputs the function value fk(R1) to the bus
 key generating circuit 1604. In the case where the value of k is normally
 found out, the drive authentication circuit 701 subsequently receives the
 random number R2 from the microcontroller 702, and inputs it to the
 function gk(R2) generating circuit 1602. The function gk(R2) generating
 circuit 1602 calculates the function gk(R2) from the value k previously
 received from the function fk(R1) generating circuit 1603 and the input
 random number R2, and outputs the obtained function value to the
 microcontroller 702 and the bus key generating circuit 1604.
 The bus key generating circuit 1604 generates a bus key based on the
 previously received function values fk(R1) and gk(R2), and outputs the bus
 key to the bus decrypting circuit 1605. On the other hand, in the case
 where the function value gk(R2) supplied to the microcontroller 702 is
 normally authenticated by the optical disk drive 509, the microcontroller
 702 switches the mode control signal, and switches the mode of the bus
 decrypting circuit 1605 to the disk key reproduction mode or the title key
 reproduction mode, so that the bus decrypting circuit is ready to be used
 for decrypting processing.
 At this time, data (encrypted disk key or encrypted title key) input from
 the SCSI control circuit 900 or the system interface circuit 700 is
 decrypted by the bus key previously retained in the bus decrypting circuit
 1605. However, it is only the bus code that decrypted by the bus
 decrypting circuit 1605, and the encrypted disk key encrypted by the
 master key and the encrypted title key encrypted by the disk key are
 output as encrypted they are to the descramble circuit 705.
 Thereafter, when reproduction data of a scrambled file is input from the
 SCSI control circuit 900 or the system interface circuit 700, the bus
 decrypting circuit 1605 is switched to the data reproduction mode by the
 mode control signal from the microcontroller 702, and transfers data to
 the descramble circuit 705 as it is without performing decrypting
 processing with the bus key.
 As described above, the drive authentication circuit 701 calculates a
 plurality of function values from the internally generated random number,
 and authenticates the drive by the matching of the drive response data
 with either one of the plurality function values. On the contrary, by
 receiving the random number and calculating the internal function values
 to transmit back, the drive authentication circuit is authenticated by the
 optical disk drive 509. In this manner, the mutual authentication
 processing is performed.
 Furthermore, for the reproduction operation, at the time of receiving the
 encrypted disk key and the encrypted title key, decrypting processing is
 performed using the bus key generated in the mutual authentication
 processing.
 Next, the protocol of the mutual authentication processing executed in the
 fifth and the sixth embodiments of the information reproducing device of
 the present invention will be described with reference to the accompanying
 drawings.
 FIG. 26 is a flow chart for explaining the mutual authentication processing
 between the optical disk drive 509 and the AV decoder card 507 or the SCSI
 control circuit incorporated AV decoder card 801.
 The mutual authentication processing is executed as necessary, such as at
 the time of reset of the apparatus and disk replacement, and when a file
 to be read is confirmed to be a scrambled file by the file managing
 information. Each step of processing will be described below. Hereinafter,
 the AV decoder card 507 or the SCSI control circuit incorporated AV
 decoder card 801 are simply referred to as an AV decoder. Furthermore,
 hereinafter, a command on the SCSI protocol is referred to as a device
 command.
 (S1700): The AV decoder generates a random number R1 based on a time
 variable key which is variable over time generated using a timer or the
 like.
 (S1701): The optical disk drive receives the random number R1 generated by
 the AV decoder, by a device command "SEND R1". At this time, when the
 optical disk drive has not stored a mutual authentication key k of the
 mounted disk yet, readout of the mutual authentication key from the sector
 header field of the scramble information sector in the lead-in area is
 executed.
 (S1702): In the case where the optical disk drive detects an error during
 the procedure of step (S1701) and the error is reported, the procedure
 goes to step (S1713). When the step (S1701) is normally ended, the
 procedure goes to step (S1703).
 (S1703): The optical disk drive receives a device command "REPORT fk(R1)",
 calculates a function fk(R1) based on the previously received random value
 R1 and a value of the mutual authentication key k read from the disk, and
 transmits the calculated result back to the AV decoder. In the processing
 described above, in the case where an error occurs, the optical disk drive
 reports the error as a result of the command processing.
 (S1704): When an error occurs during the device command "REPORT fk(R1)"
 processing, and the command processing result is an error, the procedure
 goes to step (S1713). When the processing result is a normal end, the
 procedure goes to step (S1705).
 (S1705): The AV decoder calculates a function value fi(R1) with respect to
 i (i is a positive integer) from 1 to n (n is a positive integer), using
 the internally retained function value generating circuit, and compares
 the calculated value of fi(R1) with the value of fk(R1) transmitted from
 the optical disk drive in (S1703). When the AV decoder detects the value
 of i which allows for fi(R1)=fk(R1), the AV decoder internally retains the
 value.
 (S1706): In the processing step (S1705), in the case where the AV decoder
 cannot detect the value of i which allows for fi(R1)=fk(R1), the procedure
 goes to step (S1713). In the case where the AV decoder detects the value,
 the procedure goes to step (S1707).
 (S1707): The optical disk drive receives a device command, "REPORT R2"
 command, and generates a random number based on a time variable key which
 is variable over time in the internal random number generating mechanism
 and transfers the random number to the AV decoder. In this step, in the
 case where the optical disk drive detects an error, the error is reported.
 (S1708): In the step (S1707), in the process of executing the "REPORT R2"
 command, in the case where an error occurs, the procedure goes to step
 (S1713). In the case where the step is normally ended, the procedure goes
 to step (S1709).
 (Sl709): In the step (S1708), the AV decoder which has received the random
 R2 which the optical disk drive generates by the "REPORT R2" command
 calculates a function value gk(R2) based on a constant k (=i) already
 stored in step (S1705) and the random value R2 received from the optical
 disk drive in step (S1707).
 (S1710): The AV decoder which has calculated the function value gk(R2)
 executes a device command, "SEND gk(R2)" command, and transfers the
 function value calculated in the step (S1709) to the optical disk drive.
 The optical disk drive which has received the function value gk(R2)
 calculates gk(R2) using the mutual authentication key k and the random
 number R2 in the function calculating circuit included therein.
 Thereafter, the optical disk drive compares the function value gk(R2)
 received from the AV decoder and the gk(R2) calculated by the internal
 calculating circuit. In the case where the two values are matched, a
 normal end is reported as the processing result. On the other hand, in the
 case where an error occurs during the command processing, or in the case
 where the received function value is not matched with the internally
 calculated function value, an error is reported as the command processing
 result.
 (S1711): In the step (S1710), when the command processing result is an
 error, the procedure goes to step (S1713). When the command processing
 result is a normal end, the procedure goes to step (S1712).
 (S1712): The AV decoder generates a bus key BK using the internally
 retained bus key generating circuit, based on the two function values
 fk(R1) and gk(R2) acquired in the mutual authentication processing.
 Similarly, the optical disk drive also generates a bus key BK using the
 internally retained bus key generating circuit, based on the two function
 values acquired in the mutual authentication processing. (Herein, the bus
 keys BK generated by the optical disk drive and the AV decoder in the
 mutual authentication processing are identical.)
 (S1713): In the case where an error occurs during the execution of the
 device command, the error is reported and the mutual authentication
 processing is cancelled in this step.
 By performing the mutual authentication processing in the manner as
 described above, key information can be transferred after the optical disk
 drive confirms that the data is not to be transferred to an apparatus
 which performs illegal copying. Thus, there is an effect of concealing the
 key information for performing descrambling. Therefore, an effect of
 preventing the scramble system from being illegally decrypted can be
 provided.
 Furthermore, since it is possible to perform decrypting of key information
 and descrambling of data after confirming that the apparatus from which
 the AV decoder receives data does not transfer illegally copied data, an
 effect of preventing illegally copied data from being reproduced can be
 provided.
 Furthermore, since a different bus key for every mutual authentication
 processing is generated, effects of preventing the key information from
 being illegally read and preventing the encrypting/scrambling system from
 being illegally decrypted can be provided.
 Furthermore, since different functions are used between in the case where
 the optical disk drive authenticates the AV decoder in the mutual
 authentication and in the case where the AV decoder authenticates the
 optical disk drive, the security against the act of decrypting the mutual
 authentication operation system for the purpose of illegally executing the
 mutual authentication operation is high.
 Furthermore, in the mutual authentication processing, since time variable
 keys generated by each of the optical disk drive and the AV decoder are
 used, different random number values are generated every time the mutual
 authentication processing is executed, different function values are
 transferred, and different bus keys are generated. Therefore, the security
 against the act of decrypting the mutual authentication operation system
 for the purpose of illegally executing the mutual authentication operation
 is high.
 Furthermore, by using the mutual authentication key recorded on the
 information recording medium for the mutual authentication processing, the
 security against the act of decrypting the mutual authentication operation
 system for the purpose of illegally executing the mutual authentication
 operation is high.
 Although the fourth embodiment of the information recording medium of the
 present invention has been described above as an example, the third
 embodiment of the information recording medium of the present invention
 can be processed in the same manner.
 Industrial Applicability
 The information recording medium of the present invention includes a
 lead-in area and a data recording area. Scrambled data recorded in the
 data recording area is descrambled based on the key information recorded
 in the lead-in area. Thus, by recording the key information in the lead-in
 area, security is enhanced. This is because the drive device of the
 information recording medium can directly access the lead-in area, while
 devices other than the drive device (e.g., a personal computer) cannot
 directly access the lead-in area. Furthermore, by recording the key
 information in the lead-in area, it is unnecessary to provide readout
 means dedicated to reading the key information.
 Another information recording mediums of the present invention includes the
 lead-in area and the data recording area. Scrambled data is descrambled
 based on the first key information recorded in the lead-in area and the
 second key information recorded in the data recording area. Thus, since
 the key information for descrambling is doubled, security is enhanced.
 According to the information reproducing device of the present invention,
 the mutual authentication processing is performed before the scrambled
 data is transmitted to the decoding device. By the mutual authentication
 processing, two components mutually confirms that the other is normal.
 Thus, security is enhanced.
 According to the information reproducing device of the present invention,
 the mutual authentication processing is performed between the reading
 device and the decoding device. When the mutual authentication processing
 is normally ended, the bus key information common to the reading device
 and the decoding device is generated, and key information encrypted by the
 bus key information is transmitted from the reading device to the decoding
 device. In this manner, after the mutual authentication processing is
 performed, the common bus key is further used, so that it is mutually
 confirmed that the other is normal. Thus, security is enhanced.