Patent Publication Number: US-6990589-B1

Title: Recording and/or playback apparatus and method

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to recording and/or playback apparatuses and methods suitable for a music server in which numerous music data are stored in a hard disk drive thereof and, more particularly, relates to a recording and/or playback apparatus and a method in which the stored data are protected even when the hard disk drive is changed. 
   2. Description of the Related Art 
   Music servers in which numerous music data are stored in a hard disk drive thereof have been proposed. Because of the fast access speed and large storage capacity of the hard disk drive, the numerous music data can be efficiently managed therein. A user selects desired music data from among those stored in the music server, and then the music server sends the selected desired music data to a portable recording/playback apparatus, whereby the selected desired music data can be easily played back at a place remote from the music server. 
   When the music data is stored on the hard disk drive, there is a possibility that the copyright of the music data may be violated due to illegal duplication of the music data. In order to prevent copyright violation due to illegal duplication, for example, the SCMS (Serial Copy Management System) may be adopted. SCMS prevents digital duplication beyond one generation when data is duplicated from one digital apparatus to another digital apparatus. 
   Input/output interfaces for hard disk drives are standardized, and the formats of file systems are generally standardized as well. Therefore, even though SCMS is adopted, when the hard disk drive is changed, the music data can be illegally duplicated. 
   As input/output interfaces of the hard disk drives used in digital apparatuses, IDE (Integrated Device Electronics) and SCSI (Small Computer System Interface) are standards and are widely used. The formats of file systems such as the DOS (Disk Operating System) file system and the UNIX file systems are generally standardized. Therefore, a hard disk drive which is connected to one digital apparatus and which has data stored therein using the digital apparatus can be removed from the digital apparatus, and then the hard disk drive can be connected to another digital apparatus, whereby the data can be exchanged between these two digital apparatus. 
   As long as music data is output via a regular digital audio output, SCMS prevents duplication of the data from being performed beyond one generation. However, when music data is output without using such a regular digital audio output, that is, when, as described above, the hard disk drive in one digital apparatus is changed to be connected to another digital apparatus, and the music data in the hard disk drive are duplicated to a storage media connected to the other digital device, SCMS cannot prevent this duplication. Accordingly, to deal with the above case, devices such as one disabling data to be read by digital apparatuses other than the original digital apparatus or one enabling data to become meaningless to the other digital apparatuses must be considered. 
   Recently, advanced cryptographic algorithms have been designed, and so-called cipher LSIs (large-scale integrated circuit) performing encryption or decryption on a signal have been developed. However, mounting of such a cipher LSI leads to high cost and is often inappropriate for civilian use. Protection of the copyright is desired without using so-called a cipher LSI and by applying a method which is as simple as possible. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is an object of the present invention to provide a recording and/or playback apparatus and a method which protect copyrighted data such as music data stored on a hard disk drive even when the hard disk drive is changed. 
   To this end, according to a first aspect of the invention, there is provided a recording and/or playback apparatus comprising a first storage medium having a management region and a data region, an initializing device for initializing the first storage medium so that the first storage medium comprises the management region and the data region, a generating device for generating a predetermined value when the initialization is performed, a second storage medium storing the predetermined value therein, a transforming device for applying a transformation to the predetermined value so as to be a different value, and a control device for controlling the output of the transforming device so as to store the output in the management region. 
   The recording and/or playback apparatus may further comprise a first reading device for reading the output of the transforming device stored in the management region at a time when the power is supplied and when the first storage medium is accessed, an inverse-transforming device for applying an inverse-transformation to the output of the transforming device, the second reading device for reading the predetermined value stored in the second storage medium, a comparing device for comparing the output of the inverse-transforming device and the predetermined value read by the second reading device, and an authenticating device for performing authentication based on the output of the comparing device. 
   According to a second aspect of the invention, a recording and/or playback apparatus comprises a first storage medium including a management region and a data region, a searching device for searching for an unused region of the first storage medium based on information of the management region, a logical-link forming device for forming logical links in turn based on an entry cluster number corresponding to the unused region, a transforming device for applying a transformation to the entry cluster number, and a control device for controlling the output of the transforming device and the logical links so as to store the output of the transforming device and the logical links in the management region. 
   The recording and/or playback apparatus according to the present invention may further comprise a first reading device for reading the output of the transforming device and the logical links from the management region, an inverse-transforming device for applying an inverse-transformation to the output of the transforming device read by the first reading device, and a second reading device for reading data in accordance with the logical links by setting the cluster number corresponding to the output of the inverse-transforming device as the entry cluster number. 
   According to a third aspect of the invention, a recording and/or playback apparatus comprises a first storage medium including a management region and a data region, a receiving device for receiving data from an external source, a generating device for generating a predetermined value, a transforming device for applying a transformation to the predetermined value so as to be a different value, a second storage medium for storing the output of the transforming device therein, and a first control device for controlling data to be sorted in a manner corresponding to the predetermined value, received in units of blocks by the receiving device, transferred to the first storage medium, and stored therein. 
   The recording and/or playback apparatus may further comprise a sending device for sending data, a first reading device for reading the output of the transforming device stored in the second storage medium, an inverse-transforming device for applying an inverse-transformation to the output of the transforming device, and a second control device for controlling the data to be sorted in a manner corresponding to the output of the inverse-transforming device, the data being stored in units of blocks in the first storage medium, so as to be read and so as to be sent by the sending device. 
   According to a fourth aspect of the invention, a recording and/or playback apparatus comprises a receiving device for receiving data from an external source, a generating device for generating a predetermined value, a transforming device for applying a transformation to the predetermined value so as to be a different value, a storage medium for storing the output of the transforming device therein, and a first control device for controlling a block of the data to be sorted in a manner corresponding to the predetermined value, received in process units by the receiving device, transferred to the storage medium, and stored therein. 
   The recording and/or playback apparatus may further comprise a sending device for sending data, a first reading device for reading the output of the transforming device stored in the storage medium, an inverse-transforming device for applying an inverse-transformation to the output of the transforming device, and a second control device for controlling the block of the data to be sorted in a manner corresponding to the output of the inverse-transforming device, the block of data being stored in processing units in the storage medium, so as to be read and so as to be sent by the sending device. 
   According to a fifth aspect of the invention, a recording and/or playback method comprises the steps of initializing a first storage medium so as to have a management region and a data region, generating a predetermined value when the initialization is performed, storing the predetermined value in a second storage medium and transforming the predetermined value so as to be a different value, and controlling the transformed predetermined value so as to be stored in the management region. 
   The recording and/or playback method may further comprise the steps of reading, at one time of when the power is supplied and when the first storage medium is accessed, the transformed predetermined value stored in the management region, applying an inverse-transformation of the transformation to the transformed predetermined value, reading the predetermined value stored in the second storage medium, comparing the inverse-transformed transformed predetermined value and the predetermined value read from the second storage medium, and performing authentication based on the result of the comparing step. 
   According to a sixth aspect of the invention, a recording and/or playback method comprises the steps of providing a first storage medium including a management region and a data region, searching for an unused region based on information stored in the management region of the first storage medium, forming logical links in turn based on an entry cluster number corresponding to the unused region, applying a transformation to the entry cluster number, and controlling the transformed entry cluster number and the logical links so as to be stored in the management region. 
   The recording and/or playback method may further comprise the steps of reading the transformed entry cluster number and the logical links from the management region, applying an inverse-transformation of the transformation to the transformed entry cluster number read from the management region, and reading the data based on the logical links by setting the inverse-transformed transformed entry cluster number as the entry cluster number. 
   According to a seventh aspect of the invention, a recording and/or playback method comprises the steps of providing a first storage medium including a management region and a data region, generating a predetermined value, applying a transformation to the predetermined value so as to be a different value, storing the transformed predetermined value in a second storage medium, receiving data from an external source, and controlling the data so as to be sorted in a manner corresponding to the predetermined value, received in units of blocks, transferred to the first storage medium, and stored therein. 
   The recording and/or playback method may further comprise the steps of reading the transformed predetermined value stored in the second storage medium, applying an inverse-transformation of the transformation to the transformed predetermined value, and controlling the data so as to be sorted in a manner corresponding to the inverse-transformed transformed predetermined value, the data being stored in units of blocks in the first storage medium, read, and sent. 
   According to an eighth aspect of the invention, a recording and/or playback method comprises the steps of generating a predetermined value, applying a transformation to the predetermined value so as to be a different value, storing the transformed predetermined value in a storage medium, receiving data from an external source, and controlling a data block so as to be sorted in a manner corresponding to the predetermined value, received in processing units, transferred to the storage medium, and stored therein. 
   The recording and/or playback method may further comprise the steps of reading the transformed predetermined value stored in the storage medium applying an inverse-transformation to the transformed predetermined value, and controlling the data block so as to be sorted in a manner corresponding to the inverse-transformed predetermined value, the data block being stored in processing units in the storage medium, read, and sent. 
   According to this invention, when the hard disk drive is initialized, an identity authentication parameter is transformed and is stored. When the power is supplied or when the hard disk drive is accessed, the transformed authentication parameter is inverse-transformed into the original identity authentication parameter, and then the authentication of the parameter is performed. Therefore, it can be determined whether the hard disk drive is changed. 
   According to this invention, since a file access parameter for a file entry is transformed, when the file is desired to be accessed, the file entry cluster of the desired file cannot be accessed unless the file access parameter is correctly inverse-transformed. Therefore, when the hard disk drive is changed, file access is denied. 
   According to this invention, a block transfer parameter is transformed and is stored in a flash PAM. By sorting blocks of the data in accordance with the block transfer parameter when the data is transferred, data transfer can be correctly performed only in a case in which the hard disk drive is connected to the same apparatus as the one which was connected to the hard disk drive when the data was stored. 
   According to this invention, an in-block transfer parameter is transformed and is stored in a DRAM. By sorting in-block data in accordance with the in-block transfer parameter when the in-block data is transferred, data transfer can be correctly performed only in a case in which the hard disk drive was connected to the same apparatus as the one which was connected to the hard disk drive when the data was stored. 
   Therefore, even when the hard disk drive is changed, since data duplication can be prevented, copyrighted data stored in the hard disk drive can be protected. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a diagram showing a music server according to the present invention and a system using the same; 
       FIG. 2  is a block diagram of one configuration of the music server; 
       FIG. 3  is a block diagram showing a signal flow in which music data is read from a CD-ROM drive and is stored in a hard disk drive; 
       FIG. 4  is a block diagram showing a signal flow in which compressed music data is read from the hard disk drive, is decompressed, and is output to a speaker terminal; 
       FIG. 5  is a block diagram of one configuration of a portable recording/playback apparatus; 
       FIG. 6  is a diagram showing a recording format of the hard disk drive; 
       FIG. 7  is a flowchart of a copy protection method of initializing an identity authentication system; 
       FIG. 8  is a flowchart of the copy protection method of accessing an identity authentication system; 
       FIGS. 9A and 9B  are diagrams showing recording formats of the hard disk; 
       FIG. 10  is a diagram showing a recording format of the hard disk; 
       FIG. 11  is a diagram showing the DOS file format; 
       FIG. 12  is a flowchart of a copy protection method using file access restriction; 
       FIG. 13  is a flowchart of the copy protection method using file access restriction; 
       FIGS. 14A and 14B  are diagrams showing the copy protection method using file access restriction; 
       FIGS. 15A ,  15 B, and  15 C are diagrams showing a copy protection method using sorting of transfer block data; 
       FIG. 16  is a flowchart of the copy protection method using sorting of transferred block data; 
       FIG. 17  is a flowchart of the copy protection method using sorting of transferred block data; 
       FIG. 18  is a flowchart of the copy protection method using sorting of transferred block data; 
       FIG. 19  is a flowchart of the copy protection method using sorting of transferred block data; 
       FIG. 20  is a flowchart of a copy protection method using sorting of transferred in-block data; 
       FIG. 21  is a flowchart of the copy protection method using sorting of transferred in-block data; 
       FIG. 22  is a flowchart of the copy protection method using sorting of transferred in-block data; and 
       FIG. 23  is a flowchart of the copy protection method using sorting of transferred in-block data. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Embodiments of the present invention are described below with reference to the drawings. 
   1. Outline of Music Server 
     FIG. 1  shows a music server  50 , to which the present invention is applied, and a system using the music server  50 . The music server  50  includes a server  51 , a left speaker unit  52 L, and a right speaker unit  52 R. The server  51  is provided with a display unit  53  having, for example, an LCD (liquid crystal display) panel therein, and a CD (compact disk) loading unit  54  for a CD to be loaded in the server  51 . 
   A console (not shown) having a plurality of operation switches for operating the server  51  is provided in the server  51 . The server  51  may be provided with, for example, an infrared signal reception unit receiving an infrared signal for remote-controlling the server  51  by means of a remote-controller. The server  51  includes a controller which controls various actions in accordance with predetermined programs pre-stored in a ROM (read only memory). 
   When a user loads a CD  55  via the CD loading unit  54  into the server  51  and performs predetermined operations on the console, data is read from the CD  55  and is played back via the speaker units  52 L and  52 R. When the CD  55  includes text data, such as the titles of songs, the titles of songs are displayed on the display unit  53 . 
   The music server  50  includes a mass storage medium, such as a hard disk drive. By performing predetermined operations on the console, the data read from the CD  55  loaded in the server  51  can be stored in the storage medium such as the hard disk. When the data is intended to be stored, the user can select from among recording options such as normal-speed recording in which the data is stored at the same transfer speed as the normal reading speed of the CD  55  and high-speed recording in which the data is stored at a higher transfer speed than the normal reading speed of the CD  55 . When the high-speed recording option is selected, an accounting processing is executed. After execution of the accounting processing, the CD  55  or a song recorded on the CD  55  is selected, and then the music data read from the CD  55  or the selected song can be stored at a higher transfer speed than the normal reading speed of the CD  55 . 
   In the music server  50 , the music data read from the CD  55  are compression-encoded using a predetermined method, such as ATRAC (adaptive transform acoustic coding), and then are stored as compressed music data. A hard disk having a capacity of 6 Gbytes can contain approximately 1000 songs, and a list of the songs stored in the hard disk is displayed on the display unit  53 , so that the user can select and play back a desired song from among the songs stored in the hard disk based on the list displayed on the display unit  53 . Because of random accessibility of the hard disk, a plurality of music data stored in the hard disk can be read in an arbitrary order and successively played back. 
   Various compression-encoding methods can be employed. In this embodiment, for example, as disclosed in U.S. Pat. No. 5,717,821, a method called “ATRAC 2” is employed. This is an advanced method of ATRAC, which is a compression-encoding method employed for the above-described portable recording/playback apparatus. In ATRAC 2, the music data is compression-encoded by taking advantage of a masking effect and frequency dependence of the minimum audible limit based on the characteristics of the sense of hearing and by combining transformation-encoding and entropy-encoding. By employing this method, fast encoding or decoding can be performed with a relatively small hardware configuration while the music data can still provide high-quality sound. 
   This music server  50  can be connected via a communication line  61 , such as a public telephone line, to an external system, such as an internet server  60  connected to the internet. When the music server  50  accesses the internet server  60  via the communication line  61 , various information on the internet can be obtained. For example, the internet server  60  has a database containing information about the titles of commercial music CDs. In order to access this database, the user is permitted to have an identity key for use of the database. When the user accesses the database, by performing a particular operation using the identity key, attribute information of CDs such as the title information of CDs can be obtained. 
   The internet server  60  executes the accounting processing for the music server  50  in accordance with the service provided to the user. When the above-described high-speed recording of the CD  55  is performed, the music server  50  requests permission from the internet server  60  to perform the high-speed recording. The internet server  60  executes the accounting processing for the user who requests high-speed recording for selection of a CD or a song, so that high-speed recording can be performed. 
   Here, although the accounting processing is executed on the internet server  60  in which a plurality of attribute information of CDs are stored, execution of the accounting processing is not necessarily limited to the above-described example. For example, the accounting processing may be executed on another server, which is also connected to the internet. Alternatively, the accounting processing may be executed via a private network other than the internet. 
   A portable recording/playback apparatus  70  includes a storage medium, such as a hard disk, or a flash memory. Any other storage medium may be used as long as the storage medium can keep up with the reading speed of music data. When this portable recording/playback apparatus  70  is connected to the music server  50  via a communication line  71 , music data stored in the music server  50  is transferred to the portable recording/playback apparatus  70 , and then can be stored on the storage medium of the portable recording/playback apparatus  70 . At this time, the music server  50  sets the music data to a read-protect state though the music data, which is transferred to the portable recording/playback apparatus  70 , is still stored in the storage medium of the music server  50 . The storage medium used for the portable recording/playback apparatus  70  has a capacity of approximately 200 Mbytes and can contain music data for several tens of songs. Hereinafter, a storage cell or storage medium having a semiconductor memory, such as flash memory, and a disk storage medium, such as a hard disk, are considered as the storage medium. 
   In the above-described examples, the music server  50  and the portable recording/playback apparatus  70  are connected by the communication line  71 . However, the music server  50  and the portable recording/playback apparatus  70  may be provided with corresponding interface units so as to exchange data therebetween by being directly linked to each other. Alternatively, other than an electrical link, data exchange can be performed by an infrared signal. For example, by providing the music server  50  and the portable recording/playback apparatus  70  with interfaces based on IrDA (Infrared Data Association), the music server  50  can transfer music data to the portable recording/playback apparatus  70  using an infrared signal. 
   By providing predetermined interfaces in the music server  50 , data can be exchanged between the music server  50  and various media. For example, by providing the music server  50  with an interface corresponding to a PC card  80 , music data transferred from the PC card  80  can be loaded in the music server  50 , or the music data can be exchanged between the music server  50  and a personal computer. By providing the music server  50  with a serial digital interface using an optical cable or the like, another digital music data recording/playback apparatus such as a disk recorder  81  using a compact magneto-optical disc having a diameter of 64 mm can exchange music data with the music server  50 . In this example, a disk cartridge  82  containing the compact magneto-optical disc is loaded in the disk recorder  81 , and the music data read from the magneto-optical disc in the disk cartridge  82  is supplied to the music server  50 . Likewise, the music server  50  may be provided with an interface, such as IEEE-1394, so as to be connected to a set-top box  83  for CATV (Cable Television), satellite broadcasts, or the like. 
   The PC card is a standard for card-type peripheral devices for a personal computer, which is co-established by PCMCIA (Personal Computer Memory Card International Association) in the US and JEIDA (Japanese Electronic Industry Development Association) in Japan. IEEE-1394 is an interface standard which is specified by the Institute of Electrical and Electronic Engineers. 
   The music server  50  has a WWW (World Wide Web) browser as a built-in application. When the music server  50  accesses the internet server  60  via the communication line  61 , the user searches various contents on the internet and these contents, which are written in, for example, HTML (Hypertext Markup Language), can be displayed on the display unit  53 . 
   With the above construction, for example, the user can play back music data stored in the music server  50  from the speaker units  52 L and  52 R, or the user can play back music data read from the CD  55  loaded in the music server  50  via the CD loading unit  54 . 
   When the CD  55  is loaded in the music server  50 , the music server  50  communicates with the internet server  60 , and then the title information and the like of the CD  55  can be automatically obtained via the communication line  61  from the internet server  60 . The information obtained from the internet server  60  is stored in the music server  50  and the stored title information is displayed on the display unit  53  when necessary. 
   To be more specific, the music server  50  sends characteristic information of the user (hereinafter, referred to as user information) such as user ID data of the server  50  to the internet server  60 . The internet server  60  executes verification processing and accounting processing based on the received user information. In addition, the music server  50  sends medium information of the desired CD  55 , or the CD  55  to be currently read, to the internet server  60 . Based on received medium information, the internet server  60  retrieves attribute information of the music data, such as the titles of the songs, the name of the artist, the name of the songwriter, the lyric, and the jacket image. 
   For example, the music server  50  sends TOC (Table Of Contents) information of the CD  55  as medium information to the internet server  60 . A database, in which attribute information of the music data can be retrieved based on TOC information, is constructed in the internet server  60 . The attribute information may be obtained by causing the internet server  60  to retrieve it from another WWW server on the internet. When the internet server  60  receives the TOC information as medium information, it may retrieve attribute information of the music data. For example, the internet server  60  retrieves attribute information based on playing time information of the songs of the CD  55  contained in the TOC information. 
   The internet server  60  sends the retrieved attribute information to the music server  50 . In the music server  50 , the received attribute information is displayed on the display unit  53  while a CPU  8  (see  FIG. 2 ) of the music server  50  stores the received attribute information as well as the TOC information of the CD  55 , for example, on the hard disk drive. When the internet server  60  sends an HTML file having the retrieved attribute information embedded therein to the music server  50 , the attribute information can be shown using the built-in WWW browser software. 
   When the attribute information contains another URL (Uniform Resource Locator) on the internet, the music server  50  can access a homepage represented by the URL. 
   Furthermore, by communicating data with the internet server  60 , the music server  50  can store music data of the CD  55  loaded in the music server  50  in the storage medium of the music server  50  at a higher speed than the normal reading speed of the CD  55 . For example, the music data of the CD  55  can be stored in approximately two minutes. When the music server  50  does not communicate with the internet server  60 , the music data is stored at the standard reading speed of the CD  55 , that is, the normal reading speed. 
   When the music server  50  is connected to the portable reading/playback apparatus  70  via the communication line  71 , the music data stored on the music server  50  can be transferred to the portable reading/playback apparatus  70 . The transferred music data can be read regardless of the connection between the portable reading/playback apparatus  70  and the music server  50 , and the read music data can be played back via headphones  72 . 
   2. Configuration of Music Server 
     FIG. 2  shows one configuration of the music server  50 . In the same manner as the configuration of a standard personal computer, the music server  50  includes a RAM (random access memory)  5 , a ROM (read only memory)  6 , a flash RAM  7 , and the CPU  8 , which are interconnected. A bus  40  is connected to the CPU  8 , and the CPU  8  serves as a controller that controls actions of the entire music server  50 . 
   A program for controlling actions of the music server  50  is pre-stored in the ROM  6 . The music server  50  causes the CPU  8  to perform an action in accordance with an operation of an input console  1  based on the pre-stored program. In the RAM  5  and the flash RAM  7 , a data region and a task region are temporarily allocated during execution of the program. The ROM  6  has a program loader stored therein and the program loader enables a program to be loaded in the flash RAM  7 . 
   The input console  1  includes, for example, a plurality of push or rotary operation keys and switches operated by the corresponding operation keys. The input console  1  may include a so-called “jog dial” (rotary/push operation member), touch panels on an LCD (Liquid Crystal Display), or mechanical switching mechanism that responds by being pressed. A signal generated in response to an operation of the input console  1  is supplied to the CPU  8  via the bus  40 . In accordance with the signal from the input console  1 , the CPU  8  generates a control signal for controlling an action of the music server  50 . 
   The bus  40  is connected to an infrared interface (IrDA I/F) driver  3  and/or a USB (Universal Serial Bus) driver  4 . A keyboard  2  is provided so as to be connectable to or so as to communicate with these drivers  3  and  4 . By using the keyboard  2 , for example, the title of a song, the name of an artist, or the like corresponding to the music data can be easily input. The infrared interface driver  3  or the USB driver  4  may be configured to have data pass therethrough. Alternatively, the infrared interface driver  3  and the USB driver  4  may be omitted. 
   A CD-ROM drive  9  is connected to the bus  40  and is provided with the CD loading unit  54  in which the CD  55  is to be loaded. The CD-ROM drive  9  reads music data from the CD  55  loaded therein at the normal reading speed and, furthermore, it can read music data from the CD  55  at, for example, 16× or  32 × speed. 
   The CD-ROM drive  9  may be provided so as to handle another disk storage medium containing music data, such as a magneto-optical disc, or DVD (Digital Versatile Disc), which is a trademark. Alternatively, a drive capable of handling a memory card is provided. Moreover, not only music data but also image data, text data, or program data may be read from the CD-ROM drive  9 . 
   A hard disk drive, hereinafter referred to as HDD,  10  is connected to the bus  40 . Music data read from the CD-ROM drive  9  is stored on the HDD  10 . As a preprocess for storing music data on the HDD  10 , the music data read from the CD-ROM drive  9  is supplied via the bus  40  and the DRAM (Dynamic Random Access Memory) for audio data  11  to a compression encoder  12 . 
   The compression encoder  12  performs compression encoding on music data using, for example, the compression method disclosed in U.S. Pat. No. 5,717,821. For selection of compression speeds of the music data by the compression encoder  12 , two encoding speed options, which are a high-speed mode and a low-speed mode, are available based on the control of the CPU  8 . The low-speed compression speed corresponds to the normal reading speed that the CD-ROM drive  9  provides for the CD  55 . The compression speed may be varied in accordance with, for example, the reading speed of the CD  55  provided by the CD-ROM drive  9 . The compression encoder  12  may, for example, employ an encoding method in accordance with the compression speed. 
   The compression speed of the compression encoder  12  is not necessarily varied in the above-described way. For example, variation of the compression speed of the compression encoder  12  may be performed by changing a clock frequency, or may be performed by discrete encoding sections provided for the corresponding compression speed. In the compression encoder  12  capable of performing fast compression-encoding, low-speed compression encoding may be accomplished by reducing its processing speed so that the compression encoder  12  can be adjusted to the low-speed encoding. 
   The compressed music data, which is compression-encoded by the compression encoder  12 , is stored on the HDD  10  via the DRAM  11 . 
   Although the compressed music data, which is compression-encoded by the compression encoder  12 , is constructed so as to be stored on the HDD  10 , the music data read from the CD-ROM drive  9  may be arranged to be directly supplied to the HDD  10 . 
   An audio signal input via an amplifier  14  from a microphone connected to a microphone terminal  13  or input from a line-in terminal  15  is supplied via an A/D converter  16  to the compression encoder  12  in which the audio signal can be compression-encoded for storing in the HDD  10 . Furthermore, an optical signal is supplied via an IEC958 (International Electrotechnical Commission  958 ) encoder  18  from a digital optical input  17  to the compression encoder  12  in which the audio signal input as the digital optical signal can be compression-encoded for storing on the HDD  10 . 
   Although, in this embodiment, the compression encoder  12  employs the encoding method, for example, as disclosed in U.S. Pat. No. 5,717,821, another encoding method, such as MPEG (Moving Picture Coding Experts Group), PASC (Precision Adaptive Sub-band Coding), TwinVQ (trademark), RealAudio (trademark), or LiquidAudio (trademark), may be employed. 
   A modern  20  is connected to the bus  40 . The modern  20  is connected to an external network  19  such as a public telephone line, CATV, or a wireless communication. The music server  50  communicates via the external network  19  using the modern  20 . 
   When the music server  50  is connected via the external network  19 , for example, to the internet, the music server  50  and the internet server  60  on a remote site communicate with each other. The music server  50  sends various information, to the internet server  60 , such as a request signal, medium information related to the CD  55  loaded in the CD-ROM drive  9 , user ID data and user information assigned to the music server  50 , accounting information for the user, and the like. 
   When various information, such as medium information and the user information, is sent to the internet server  60 , the internet server  60  executes the verification processing and the accounting processing in accordance with the received user information, retrieves the attribute information of the music data in accordance with the received medium information, and sends the attributed data to the music server  50 . 
   In this embodiment, although there is shown the example in which the attribute information of the music data is supplied to the music server  50 , the music data as such may be directly supplied to the music server  50  in accordance with the request of the user. This means that the user can download the music data via the music server  50  from the internet server  60 . The music data can be downloaded in accordance with the medium information. This allows, for example, a predetermined bonus track of the CD  55  to be obtained by downloading. 
   When the compressed music data, which is compression-encoded by the compression encoder  12  and which is stored on the HDD  10 , is read from the HDD  10  for playback, the read data is supplied via the bus  40  to a compression decoder  21 . The compression decoder  21  decodes the compressed music data. The decoded data is output via a D/A converter  22 , an amplifier  23 , and a speaker terminal  24  to the speaker units  52 L and  52 R in which the music data can be played back. Although not shown in  FIG. 2 , two channels corresponding to stereo output are provided from the D/A converter  22  to the speaker terminal  24  via the amplifier  23 . Likewise, two channels of the speaker terminal  24  corresponding to the L-channel and the R-channel of stereo output are provided. 
   The compression decoder  21  employs a decoding method that corresponds to the encoding method employed by the compression encoder  12 . Without using particular hardware, the compression encoder  12  and the compression decoder  21  may be implemented in software using the CPU  8 . 
   A liquid crystal display element (hereinafter, referred to as LCD)  26 , which constitutes the display unit  53 , is connected to the bus  40  via an LCD driver  25 . The CPU  8  supplies a drawing control signal to the LCD driver  25  via the bus  40 . The supplied drawing control signal causes the LCD driver  25  to drive the LCD  26  to show a predetermined display on the display unit  53 . 
   For example, an operation menu of the music server  50  or a title list of the compressed music data stored on the HDD  10  is displayed on the display unit  53 . Since data based on the decoded attribute information sent from the internet server  60  is supplied to the HDD  10 , the title list is displayed on the display unit  53  using the data based on the decoded attribute information stored on the HDD  10 . Furthermore, for example, a folder or jacket image data corresponding to the music data which is selected to be played back is displayed on the LCD  26  based on the attribute information sent from the internet server  60 . 
   When the user operates a pointing device of the input console  1  or the keyboard  2  based on what is displayed on the display unit  53 , the CPU  8  controls reading of the selected music data. In addition, based on what is displayed on the display unit  53 , the selected music data may be deleted, or may be copied onto or moved to an external apparatus. For example, when the input console  1  includes a touch panel provided on the LCD  26 , and the user touches the touch panel in accordance with what is displayed on the display unit  53 , the music server  50  can be operated. Thus, the display unit  53  serves as an interface between the user and the music server  50 , whereby the music data stored on the HDD  10  can be managed and controlled. 
   In this example, IEEE-1394 and the PC card are used as interfaces between the music server  50  and general external information devices. An IEEE-1394 interface  28  is connected via an IEEE-1394 driver  29  to the bus  40 . Likewise, a PC card slot  31  is connected via a PC card driver  30  to the bus  40 . 
   The IEEE-1394 interface  28  enables data to be exchanged between the music server  50  and, for example, a personal computer. Furthermore, the IEEE-1394 interface  28  enables music data to be obtained from a satellite broadcasting IRD (Integrated Receiver/Decoder), a compact magneto-optical disc or an optical disc having a diameter of approximately 64 mm, DVD, a digital video tape, or the like. By loading a PC card into the PC card slot  31 , the music server  50  can be easily expanded for various peripheral devices, such as an external storage device, another external media drive, a modern, a terminal adapter, a capture board, or the like. 
   An interface  34  is provided for exchanging music data between the music server  50  and a corresponding other recording/playback apparatus. As the corresponding other recording/playback apparatus, for example, the portable recording/playback apparatus  70  may be used. Alternatively, another music server  50  may be used as the corresponding other recording/playback apparatus. 
   The interface  34  is connected via an interface driver  33  to the bus  40 . The corresponding other recording/playback apparatus is provided with an interface  35  that corresponds to the interface  34 . When the interfaces  34  and  35  are electrically connected with a predetermined connection line  71 , for example, the music data stored on the HDD  10  can be transferred from the music server  50  to the corresponding other recoding/playback apparatus. 
     FIG. 3  shows a schematic signal flow from reading music data from the CD-ROM drive  9  to storing read music data on the HDD  10 . The music data read from the CD-ROM drive  9  is transferred via the bus  40  to the DRAM  11 . The DRAM  11  serves as a buffer memory in which the transferred data is temporarily stored. The music data read from the DRAM  11  at a predetermined timing is supplied via the bus  40  to the compression encoder  12 . The compression encoder  12  encodes at a predetermined compression speed in accordance with the reading speed of the CD-ROM drive  9  as described above. The music data is compression-encoded by the compression encoder  12  and is again temporarily stored in the DRAM  11 , which serves as the buffer memory. The compressed music data read from the DRAM  11  at a predetermined timing is supplied via the bus  40  to the HDD  10  in which the compressed music data is stored. At this time, as described above, the music server  50  receives the attribute information of the CD  55  currently read from the CD-ROM drive  9  from the internet server  60 , stores the attribute information in the HDD  10 , and forms this attribute information and the compressed music data into one data block. The CPU  8  controls the compressed music data and the attribute information as one data block. 
     FIG. 4  shows a schematic signal flow from reading of compressed music data from the HDD  10  to output of the music data to the speaker terminal  24 . The compressed music data read from the HDD  10  is supplied via the bus  40  to the DRAM  11  and is temporarily stored in the DRAM  11  as the buffer memory. The compressed music data is read at a predetermined timing from the DRAM  11  and is supplied via the bus  40  to the compression decoder  21 . The compression decoder  21  decodes the compressed music data to the original music data, and the decoded music data is supplied to the D/A converter  22 . The D/A converter  22  converts the digital music data into an analog audio signal. The analog audio signal is amplified by the amplifier  23  and is output to the speaker terminal  24 . When a speaker is connected to the speaker terminal  24 , the music data is played back from the speaker. At the same time, the CPU  8  decodes the attribute information that is read from the HDD  10  along with the compressed music data, and the attribute information such as the title is displayed on the display unit  53 . 
   3. One Example of Portable Recording/Playback Device 
     FIG. 5  shows one configuration of the portable recording/playback apparatus  70 , which serves as the corresponding other recording/playback apparatus. The configuration of the portable recording/playback apparatus  70  is substantially identical to that of the music server  50  shown in  FIG. 2 . The portable recording/playback apparatus  70  is normally separated from the music server  50  by detaching the interface  35  of the portable recording/playback apparatus  70  from the interface  34  of the music server  50  and is used as a single unit. 
   In the same manner as the configuration of a standard personal computer, the portable recording/playback apparatus  70  includes a RAM  103 , a ROM  104 , and a CPU  105 , which are interconnected. In the same manner as the configuration of a standard personal computer, the portable recording/playback apparatus  70  may be provided with a flash RAM. The CPU  105  serves as a controller that controls actions of the portable recording/playback apparatus  70 . 
   A program for controlling actions of the portable recording/playback apparatus  70  is pre-stored in the ROM  104 . The portable recording/playback apparatus  70  causes the CPU  105  to perform an action in accordance with an operation of an input console  102  based on the pre-stored program. In the RAM  103 , a data region and a task region are temporarily allocated during execution of the program. An input console  102  includes, for example, a plurality of push or rotary operation keys and switches operated by these corresponding operation keys. The input console  102  may include a jog dial, which is a rotary/push operation member, touch panels on an LCD, or mechanical switching mechanism that responds by being pressed. A signal generated in response to an operation of the input console  102  is supplied to the CPU  105  via a bus  130 . In accordance with the signal from the input console  102 , the CPU  105  generates a control signal for controlling an action of the portable recording/playback apparatus  70 . 
   When the music server  50  reads desired music data from the HDD  10 , and the music data is requested to be transferred to the portable recording/playback apparatus  70 , it is transferred to the recording/playback apparatus  70  via the interfaces  34  and  35  and a connection line establishing a connection between the interface  34  and the interface  35 . At the same time, along with the music data, the attribute information of the music data is also supplied to the portable recording/playback apparatus  70 . When the music server  50  and the portable recording/playback apparatus  70  each have mounting parts corresponding to each other, since these mounting parts enable the interfaces  34  and  35  to be directly linked to each other, music data is transferred between the music server  50  and the portable recording/playback apparatus  70  without the connection line. In addition, when the portable recording/playback apparatus  70  and the music server  50  are each provided with interfaces using IrDA, music data is transferred using an infrared signal between the music server  50  and the portable recording/playback apparatus  70 . 
   The music data transferred from the music server  50  to the other portable recording/playback apparatus  70  is supplied via an interface driver  101  and the bus  130  to an HDD  106 , which serves as music data storage. 
   Alternatively, as the music data storage of the portable recording/playback apparatus  70 , a flash RAM may be used. Other storage media such as a magneto-optical disk may be used as long as the storage medium can keep up with the reading speed of music data. In a case in which the music storage medium of the portable recording/playback apparatus  70  having a storage capacity of approximately 200 Mbytes is used, several tens of songs can be stored. The HDD  106  of the portable recording/playback apparatus  70  contains the music data sent from the music server  50  as well as the attribute information of the music data. 
   In this example, the music data, which is transferred from the music server  50  to the HDD  106  of the portable recording/playback apparatus  70 , has already been compression-encoded in the music server  50 . The portable recording/playback apparatus  70  may store non-compression-encoded music data in the HDD  106 . For example, the music data read from the CD  55  loaded in the CD-ROM drive  9  of the music server  50  is supplied unmodified via the interface driver  101  to the portable recording/playback apparatus  70 . However, when the uncompressed music data is supplied to the portable apparatus  70 , the size of the music data which can be recorded in the portable apparatus  70  is considerably reduced. 
   As a preprocess for recording the music data in the HDD  106 , the supplied music data is temporarily stored in a DRAM (for an audio signal)  107  which is connected to the bus  130 . The music data read from the DRAM  107  is supplied via the bus  130  to a compression encoder  108 . The compression encoder  108  performs compression encoding of the music data with an encoding method equivalent to that of the compression encoder  12  of the music server  50 . The music data compressed by the compression encoder  108  is supplied to the DRAM  107  and is temporarily stored therein. Finally, the compressed music data temporarily stored in the DRAM  107  is read and is stored in the HDD  106 . 
   In this example, an audio signal input via an amplifier  110  from a microphone connected to a microphone terminal  109  or an audio signal input from a line-in terminal  111  is supplied via an A/D converter  112  to the compression encoder  108 . The compression encoder  108  can perform compression-encoding of the audio signal from the A/D converter  112  so that the compressed audio signal can be recorded in the HDD  106 . In addition, a digital optical signal is supplied via an IEC-958 encoder  114  from a digital optical input terminal  113  to the compression encoder  108 . The audio signal, which is input as the optical signal, is compression-encoded so that the compressed audio signal can be recorded in the HDD  106 . In the case in which the portable apparatus  70  is dedicated for reading only compressed music data, the above A/D converter  112 , encoder  108 , and the like which are required for recording processing can be omitted. 
   When the compressed music data is read from the HDD  106  for reading, it is supplied via the bus  130  to a compression decoder  115 . The compression decoder  115  decodes the compressed music data by performing decompression processing and the decompressed music data is output via a D/A converter  116  and an amplifier  117  to a speaker terminal  118 . The speaker terminal  118  is connected to the headphones  72  with the music data can be listened to. Although not shown in  FIG. 5 , two channels corresponding to stereo output are provided from the D/A converter  116  to the speaker terminal  118  via the amplifier  117 . Likewise, two channels of the speaker terminal corresponding to the L-channel and the R-channel of stereo output are provided. 
   An LCD  120  is connected via an LCD driver  119  to the bus  130 . The CPU  105  supplies a drawing control signal via the bus  130  to the LCD driver  119 . The supplied drawing control signal causes the LCD driver  119  to drive the LCD  120  to display a predetermined display on the LCD  120 . An operation menu of the portable apparatus  70  or a title list of the music data stored in the HDD  106  is displayed on the LCD  120 . For example, a folder or jacket image corresponding to the music data which is selected to be played back is displayed on the LCD  120  based on the attribute information stored in the HDD  106 . 
   When a user operates a pointing device of the input console  102  based on what is displayed on the LCD  120 , one of the compressed music data stored in the HDD  106  is selected and played back. In addition, based on what is displayed on the LCD  120 , deletion, duplication, or moving of the selected music data may be performed. For example, by touching the touch panel of the input console  102  in accordance with what is displayed on the LCD  120 , the user can operate the portable apparatus  70 . Thus, the LCD  120  serves as an interface between the user and the portable apparatus  70 , whereby the compressed music data stored on the HDD  106  can be managed or controlled for recording and playback. 
   The portable apparatus  70  is driven by a battery, not shown. Because of this, the portable apparatus is provided with a power supply unit, which utilizes a common secondary battery or a dry battery as a power supply source, and is also provided with a charging unit. When the music server  50  and the portable apparatus  70  are directly linked by the connection line or the mounting parts, and the music data is transferred, the music server  50  also supplies electrical power to the charging unit to charge the secondary battery of the portable apparatus  70 . As the power supply, either the power source that uses the dry battery or the chargeable power source that uses the secondary battery may be used. 
   4. Protection Against Data Duplication Due to Identity Authentication 
   The above-described system can duplicate music data from the music server  50  to the portable apparatus  70 , the disk recorder  81  connected to the music server  50 , or the like. However, unconstrained duplication may lead to violation of the music data copyright. As a device for preventing the copyright from being violated due to illegal duplication, SCMS is known. In a case in which the HDD  10  is removed from the music server  50 , the HDD  10  is connected to another apparatus, and music data stored on the HDD  10  is duplicated to a recording/playback apparatus connected to the other apparatus, illegal-copy protection fails because SCMS does not work in such a case. Accordingly, even when the hard disk is changed in the above-described manner, duplication must be restricted so that the copyrighted data is protected. 
   To solve the above problem, using a parameter obtained by means of a transformation employing a mapping intrinsic to an apparatus, the present invention prevents the copyrighted data from being duplicated even when the hard disk drive is changed. 
   An example is described in which changing of the hard disk drive is determined by means of authentication employing the mapping-transformed parameter. 
   As the interface of the HDD  10 , a typical interface such as IDE (Integrated Device Electronics) or SCSI (Small Computer System Interface) may be used. Data is stored as a file in the HDD  10 . 
   As shown in  FIG. 6 , a disk recording area of the HDD  10  includes a management area  201  and a file record area  202 . The management area  201  includes a file entry table and a linked list. Furthermore, the management area  201  includes a parameter area. 
   The parameter provided in the management area  201  of the HDD  10  is an identity authentication parameter b 1 . When the power is supplied, the identity authentication parameter b 1  serves to determine whether the HDD  10  is changed. 
   This identity authentication parameter b 1  stored in the management area  201  is obtained by means of the transformation employing an authentication mapping f 1  intrinsic to the apparatus, which in this case is the music server  50 . This means that the identity authentication parameter b 1  is obtained by transforming an actual parameter a 1  (parameter for identity authentication) using the mapping f 1  so that b 1 =f 1 (a 1 ) holds. 
   In the ROM  6 , a program for computation using the mapping f 1  for transformation and for computation using an inverse mapping f 1   −1  for inverse-transformation is stored. The above-described transformation from the actual parameter a 1  to the identity authentication parameter b 1  is performed in accordance with this program stored in the ROM  6 . The inverse-transformation from the identity authentication parameter b 1  to the actual parameter a 1  is also performed in accordance with this program stored in the ROM  6 . 
   The parameter a is an arbitrary value in the domain of an arbitrary mapping f for which an inverse mapping exists. The inverse mapping (b=f −1 (a)) of the parameter and the parameter b are in one-to-one correspondence. As described above, the mapping and inverse mapping computation program is stored in the ROM  6  and the mapping and inverse mapping are intrinsic to the apparatus. For example, f 1 =I (identity mapping f 1   −1 =I) may be set as the mapping f 1 . 
     FIGS. 7 and 8  show flowcharts of identity authentication processing. The HDD  10  must be initialized before being used. The initialization of the HDD  10  is performed before its shipment or its use by applying a HDD initialization command. 
   In this initialization process at step S 11 , normal initialization processing is executed. For example, the disk of the HDD  10  is divided into clusters, and each cluster is numbered. In the management area  201 , the file entry table and the linked list are created, initialized, and so forth. As a result of executing the initialization processing, all data stored in the HDD  10  are deleted. 
   At step S 12 , the CPU  8  generates the actual parameter a 1 , which is the parameter for identity authentication. The parameter a 1  is stored in an authentication parameter area of the flash RAM  7 . At step S 13 , the computation program using the mapping f 1  for transforming the parameter a 1 , the program being stored in the ROM  6 , is activated. The computation program computes b 1 =f 1 (a 1 ), thus obtaining the parameter b 1  based on the parameter a 1 . At step S 14 , the transformed identity authentication parameter b 1  is stored in a parameter area of the management area  201  of the HDD  10 . 
   When the disk initializing processing of the HDD  10  is executed, the identity parameter b 1  transformed using the mapping intrinsic to the apparatus is stored in the parameter area of the management area  201  of the HDD  10 . 
   When the power is supplied or when the HDD  10  is accessed, the identity authentication is performed, which determines whether the HDD  10  is changed. When this identity authentication is performed, the parameter b 1  is used. 
     FIG. 8  shows a flowchart of the identity authentication process which is executed when the power is supplied or when the HDD  10  is accessed. At step S 21 , the parameter b 1  is read from the parameter area of the management area  201  of the HDD  10  when the power is supplied or when the HDD  10  is accessed. At step S 22 , the computation program using the inverse mapping f 1   −1  for inverse-transforming the parameter b 1 , the program being stored in the ROM  6 , is activated. The computation program computes a 1 =f 1   −1 (b 1 ), thus obtaining the parameter a 1  based on the parameter b 1 . 
   At step S 23 , the identity authentication parameter a 1  stored in the flash RAM  7  as shown at step S 12  in  FIG. 7  is read. At step S 24 , the parameter a 1  obtained at step S 22  and the parameter a 1  obtained at step S 23  are compared. 
   When the HDD  10  is not changed, both parameters a 1  must be equal. If both parameters are equal, the process proceeds to step S 25  in which the validity of the HDD  10  is verified, otherwise the process proceeds to step S 26  in which the validity of the HDD  10  fails to be verified. 
   5. Protection Against Data Duplication Due to File Access Restricted 
   An example in which file access is denied when the HDD  10  is changed is described. 
   As shown in  FIG. 6 , the disk recording area of the HDD  10  is divided into the management area  201  and the file record area  202 , and the management area  201  is divided into a file entry table  210  and a linked list  220 . As shown in  FIG. 9A , the file entry table  210  contains the file entries of the files stored in the HDD  10 . As shown in  FIG. 9B , the file entry of each file contains a file name  211 , a parameter field  212 , a file size  213 , creation time and modification time  214 , and other attribute information  215 . 
   As shown in  FIG. 10 , the linked list  220  shows correspondence relationships between cluster numbers CL 0 , CL 1 , . . . and their subsequent cluster numbers LCLO, LCL 1 , . . . . By traversing this linked list, a group of clusters is formed into a file. A unique number such as 0 is contained in the final cluster number of the file. 
   Such a file format structure is implemented in, for example, the DOS file format. In the DOS file format, the management area includes a directory region and FAT (File Allocation Table). As shown in  FIG. 11 , the directory region includes the file name, the extension thereof, the attribute, the creation time and date, the modification time and date, the FAT entry number, and the file size information. The FAT region includes link information of files, each of which consists of a set of clusters. 
   In the DOS file format, the entry cluster number of a file is obtained based on a FAT entry number of the directory region, and the FAT table shows the subsequent cluster numbers of the file. When a desired file is accessed, the entry cluster of the file is accessed based on the FAT entry number of the directory region, and then the subsequent clusters of the file are accessed based on the FAT table. Therefore, the directory region is the file entry table  210  and the FAT region is the linked list  220 . 
   The parameter field  212  in  FIG. 9B  contains the value of a file access parameter b 2 . The file access parameter b 2  represents the entry cluster number of the file, which corresponds to the FAT entry number in the DOS file format shown in  FIG. 11 . The file access parameter b 2  is transformed using a mapping f 2  intrinsic to the apparatus, that is, the parameter b 2  is obtained using the mapping f 2  of an actual parameter a 2  as follows: b 2 =f 2 (a 2 ). Because of this, as long as the parameter b 2  is not correctly transformed into the original parameter a 2 , the access of the entry cluster of the desired file fails. When the HDD  10  is changed, because the parameter b 2  cannot be correctly transformed into the parameter a 2 , the entry cluster of the desired file cannot be accessed. 
   As the mapping f 2 , for example, f 2 (z)=z+1 is given. In this case, as the inverse mapping of f 2 (z), the inverse mapping f 2   −1 (z)=z −1  is obtained. Preferably, the inverse mapping f 2   −1 (z) is an identity mapping of the f 2 (z). 
     FIGS. 12 and 13  show flowcharts of file access processes when data is stored on the HDD  10  and when data is read from the HDD  10 , respectively. 
     FIG. 12  shows a file data storing process. When a new file is desired to be recorded on the HDD  10 , at step S 31 , an unused cluster is obtained by searching the linked list. At step S 32 , an entry cluster number, i.e., the parameter a 2 , is determined based on the unused cluster number found. 
   At step S 33 , the computation program using the mapping f 2  for transforming the file access parameter a 2 , the program being stored in the ROM  6 , is activated, thus obtaining the parameter b 2  based on the parameter a 2 . At step S 34 , the transformed file access parameter b 2  is stored in the parameter field  212  of the file entry ( FIGS. 9A and 9B ). 
   At step S 35 , data of the file is stored in the unused entry cluster. At step S 36 , the process determines whether data of the file is to be stored in subsequent unused clusters. If the result of the determination is affirmative, at step S 37 , data of the file is stored in a subsequent unused cluster. 
   If the result of the determination is negative, at step S 38 , the process determines that file data storing process terminates. The linked list is updated based on link information of the clusters having the data of the file stored therein. At step S 39 , the file data storing process terminates. 
     FIG. 13  shows a file data reading process. When a desired file is read, at step S 41 , the entry cluster number b 2  of the desired file is read from the parameter field  212  of the file entry. 
   At step S 42 , the computation program using the inverse mapping f 2   −1  for inverse-transformation of the entry cluster number b 2 , the program being stored in the ROM  6 , is activated. The computation program computes a 2 =f 2   −1 (b 2 ), thus obtaining the actual parameter a 2  based on the parameter b 2 . 
   At step S 43 , the cluster having the cluster number pointed to by the inverse-transformed file access parameter a 2  is accessed. At step S 44 , data is read from the cluster having the cluster number pointed to the parameter a 2 . 
   At step S 45 , the process determines whether this cluster has a subsequent cluster based on the linked list. If the result of the determination is affirmative, the process proceeds to step S 46  in which the subsequent cluster is accessed, otherwise the process proceeds to step S 47  in which, since the process determines that there is no more data to read from this file, the file data reading process terminates. 
   In this example, the parameter that represents the entry cluster number of the file is transformed using the mapping intrinsic to the apparatus. Because of this, when the HDD  10  is changed, it is impossible to access the appropriate file entry. Accordingly, protection of the contents in the HDD  10  can be achieved. 
   For example, as shown in  FIG. 14A , information is stored in file entries. When a file having the file name “ABC” is desired to be accessed, “4” is contained in the parameter field of the file entry of the file “ABC”. 
   In this case, since the parameter value b 2  is obtained as “4” by transformation, this value is not the actual parameter a 2 . Accordingly, in order to obtain the actual parameter a 2 , this parameter b 2  must be inverse-transformed using the inverse mapping f 2   −1 . 
   As shown in  FIG. 14A , the parameter “4” is transformed into the actual parameter “3” by means of the inverse mapping program (parameter transformation). Therefore, when the file having the file name “ABC” is accessed, the cluster having the cluster number “3”, which indexes the cluster CL 3  ( FIG. 14B ), is accessed. 
   In accordance with the linked list shown in  FIG. 14B , clusters CL 6 , CL 1 , CL 9 , and CL 11  are accessed in turn. Since the cluster CLl 1  contains “0” as the next cluster number, file access is stopped at the cluster CL 11 . 
   6. Protection Against Data Duplication Due to Sorting of Transferred Block Data 
   An example, in which transferred block data are sorted so that data transfer can be correctly performed in the hard disk only in a case in which the hard disk is connected to the same apparatus as the one which was connected to the hard disk when the data was stored, is described. 
   When music data is transferred from outside to the HDD  10  of the music server  50 , the transferred data is temporarily stored in the DRAM  11 , is read in certain units (blocks) from the DRAM  11 , and then is stored in the HDD  10 . On the other hand, when the music data is read from the HDD  10 , the read data is temporarily stored on the DRAM  11 , is read in certain units (blocks) from the DRAM  11 , and then is output. A DMA (Direct Memory Access) controller  37  performs direct memory access control of the data transfer. 
   As shown in  FIG. 15A , the DRAM  11  is divided into a plurality of banks, BNK 0 , BNK 1 , BNK 2 , . . . , and as shown in  FIG. 15B , each bank is divided into a plurality of blocks, BLK 0 , BLK 1 , BLK 2 , . . . The size of each block corresponds to the size of the cluster. 
   When the music data is transferred in certain units from outside to the HDD  10 , scrambling of the data can be achieved by sorting the data obtained by changing the data transfer sequence or by changing the offset of the transferred data. 
   In this example, a block sort parameter a 3  is transformed into a parameter b 3  using a mapping f 3  intrinsic to the apparatus and the transformed parameter b 3  is stored in the flash RAM  7 . This enables data blocks stored in the HDD  10  to be sorted in accordance with the parameter a 3 . Therefore, when the HDD  10  is not connected to the same apparatus as the one which was connected to the HDD  10  when the data was stored, data transfer cannot be correctly performed. 
     FIGS. 16 and 17  show the data block transfer processes, wherein  FIG. 16  shows the process in which the data is stored in the HDD  10 , and  FIG. 17  shows the process in which the data is read from the HDD  10 . 
   In  FIG. 16 , when data is stored in the HDD  10 , the CPU  8  generates the block sort parameter a 3  (step S 51 ). At step S 52 , the computation program using the mapping f 3  for transforming the parameter a 3 , the program being stored in the ROM  6 , is activated. The computation program computes b 3 =f 3 (a 3 ), thus obtaining the parameter b 3  based on the parameter a 3 . At step S 53 , the parameter b 3  is stored on the parameter field of the flash RAM  7 . 
   At step S 54 , the data is transferred to be stored in the HDD  10 . At step S 55 , blocks of the data, in which the number of the blocks is based on the parameter a 3 , are transferred in the data transfer manner based on the parameter a 3  from a data input unit, including the compression encoder  12 , the A/D converter  16 , the IEC-958 encoder  18 , the input terminals  13 ,  15 , and  17 , and the amplifier  14  to the DRAM  11 . 
   In  FIG. 17 , when the data is read, the parameter b 3  is read from the parameter field of the flash RAM  7  (step S 61 ). At step S 62 , the computation program using the inverse mapping f 3 - 1  for inverse-transforming the parameter b 3 , the program being stored in the ROM  6 , is activated. The computation program computes a 3 =f 3   −1 (b 3 ), thus obtaining the parameter a 3  based on the parameter b 3 . 
   When the data is transferred to be read from the HDD  10  (step S 63 ), the data is transferred in the data transfer manner in accordance with the parameter a 3  from the DRAM  11  to a data output unit (including the compression decoder  21 , the D/A converter  22 , and the amplifier  24 ) (step S 64 ). 
   As a possible data transfer manner in accordance with the parameter, there is a manner in which, after blocks of data in which the number of the blocks corresponds to the parameter a 3 , are transferred to a temporary storage location, the blocks of data are transferred from the temporary storage location in reverse order of the blocks of data transferred to the temporary storage location. That is, when the data is stored in the HDD  10 , after the blocks of data, in which the number of the blocks corresponds to the parameter a 3 , are transferred from the data input unit to the DRAM  11 , the blocks are transferred from the DRAM  11  to the HDD  10  by reversing the order of the blocks transferred from the data input unit to the DRAM  11 . 
   For example, in a case in which the parameter a 3  is equal to 2, as shown in  FIG. 18 , one data block is transferred from the data input unit to the DRAM  11  and is stored in BLK N of the DRAM  11  (step S 71 ). At step S 72 , another data block is transferred from the data input unit to the DRAM  11  and is stored in BLK (N+1) of the DRAM  11 . Thus, after those two blocks of the data are transferred from the data input unit to the DRAM  11 , the data stored in BLK (N+1) is transferred from the DRAM  11  to the HDD  10  (step S 73 ). At step S 74 , the data stored in BLK N is transferred from the DRAM  11  to the HDD  10 . 
   By transferring data in this manner, the data are stored in the HDD  10  so as to be alternately exchanged block by block. 
   When data is read from the HDD  10 , as shown in  FIG. 19 , one block (cluster) of data is read from the HDD  10 , is transferred from the HDD  10  to the DRAM  11 , and is stored in the BLK N of the DRAM  11  (step S 81 ). At step S 82 , another block of data is read from the HDD  10 , is transferred from the HDD  10  to the DRAM  11 , and is stored in the BLK (N+1). Thus, after these two blocks of the data are transferred from the HDD  10  to the DRAM  11 , the data stored in the BLK (N+1) is transferred from the DRAM  11  to the data output unit (step S 83 ). At step S 84 , the data stored in the BLK N is transferred from the DRAM  11  to the data output unit. 
   Although the sorting method employed in the above-described example is performed by reversing the transfer order of blocks in which the number of the blocks corresponds to the parameter, other sorting methods may be employed. 
   7. Protection Against Data Duplication Due to Sorting of Transferred In-Block Data 
   An example is described, in which transferred in-block data are sorted so that in-block data transfer can be correctly performed in the hard disk only in a case in which the hard disk is connected to the same apparatus as the one which was connected to the hard disk when the data was stored. 
   As shown in  FIGS. 15A and 15B , the DRAM  11  is divided into a plurality of blocks BLK 0 , BLK 1 , BLK 2 , . . . As shown in  FIG. 15C , each block includes a header region HA, and minimum data units mPS 0 , mPS 1 , mPS 2 , . . . The minimum data units mPS 0 , mPS 1 , mPS 2 , . . . are minimum-processing units for in-block data transfer. For example, in a case in which audio data is compressed and is transferred using ATRAC, the minimum-processing unit may be a sound group or the like. 
   When the music data are transferred from outside to the HDD  10 , scrambling of data can be achieved by sorting the minimum-processing units of data within one block. 
   In this example, the data transfer order, the offset, or the like of the minimum-process units of data of one block is set as a parameter a 4 . This parameter a 4  is transformed into a parameter b 4  using a mapping f 4  intrinsic to the apparatus, and the transformed parameter b 4  is stored in the header region HA of the DRAM  11 . Thus, the data stored in the HDD  10  are sorted in accordance with the parameter a 4 . Therefore, when the HDD  10  is not connected to the same apparatus as the one which was connected to the HDD  10  when the data was stored, data transfer cannot be correctly performed. 
   The parameter b 4  stored in the header region HA is an in-block transfer parameter and is transformed using the mapping f 4  intrinsic to the apparatus. 
     FIGS. 20 and 21  show in-block data transfer processes, wherein  FIG. 20  shows the process in which the data is stored in the HDD  10 , and  FIG. 21  shows the process in which data is read from the HDD  10 . 
   In  FIG. 20 , when the data is stored in the HDD  10 , the CPU  8  generates the in-block transfer parameter a 4  (step S 91 ). At step S 92 , the computation program using the mapping f 4  for transforming the parameter a 4 , the program being stored in the ROM  6 , is activated. The computation program computes b 4 =f 4 (a 4 ), thus obtaining the parameter b 4  based on the parameter a 4 . At step S 93 , the parameter b 4  is stored in the header region HA of the DRAM  11 . 
   At step S 94 , the data is transferred to be stored on the HDD  10 . At step S 95 , a minimum-processing unit of the data of the block is transferred from the data input unit to the HDD  10  in the manner based on the parameter a 4  and in an order based on the parameter a 4 . 
   In  FIG. 21 , when the data is read from the HDD  10 , the parameter b 4  is read from the parameter field of the header region HA (step S 101 ). At step S 102 , the computation program using the inverse mapping f 4   −1  for inverse-transforming the transformed in-block data transfer parameter b 4 , the program being stored in the ROM  6 , is activated. The computation program computes a 4 =f 4   −1 (b 4 ), thus obtaining the original in-block data transfer parameter a 4  based on the parameter b 4 . 
   At step S 103 , the data is transferred to be read from the HDD  10 . At step S 105 , minimum-processing units of the data of the block are transferred in the manner based on the parameter a 4 . 
   As a possible data transfer manner in accordance with the parameter, there is a manner in which data are offset by a number of the processing units corresponding to the parameter. That is, when the data are stored on the HDD  10 , by shifting the data by the number of the processing units corresponding to the parameter a 4 , the data are transferred from the data input unit to the DRAM  11  and are further transferred from the DRAM  11  to the HDD  10 . 
   For example, in a case in which the parameter a 4  is equal to 3, as shown in  FIG. 22 , when data are stored in the HDD  10 , one processing unit of the data is transferred from the data input unit to the DRAM  11  and is stored in mPS 2  which is offset by three processing units from the top of a block of the DRAM  11  (step S 111 ). Another processing unit of the data is transferred from the data input unit to the DRAM  11  and is stored in mPS 3  (step S 112 ). Likewise, processing units of the data are transferred one after another from the data input unit to the corresponding minimum data units of the DRAM  11 , i.e. mPS 4 , mPS 5 , . . . . 
   After one processing unit of the data is transferred to the last minimum data unit mPSZ of the block (step S 113 ), the subsequent processing unit of the data is transferred to the first minimum data unit mPS 0  of the block (step S 114 ), and the further subsequent processing unit of the data is transferred to mPS 1  (step S 115 ). 
   When data is transferred to be read, as shown in  FIG. 23 , one processing unit of the data stored in mPS 2 , which is offset by three processing units from the top of a block of the DPAM  11 , is transferred to the data output unit (step S 121 ). At step S 122 , one processing unit of the data stored in mPS 3  of the block of the DRAM  11  is transferred to the data output unit. Likewise, processing units of the data are each transferred one after another from corresponding minimum data units of the DRAM  11 , that is, mPS 4 , mPS 5 , . . . to the data output unit. 
   After one processing unit of the data is transferred from the last minimum data unit mPSZ of the block to the data output unit (step S 123 ), one processing unit of the data is transferred from the first minimum data unit mPS 0  of the block to the output data unit (step S 124 ), and one processing unit of the data is transferred from mPS 1  to the data output unit (step S 125 ). 
   Although the sorting method employed in the above-described embodiment is performed by shifting in-block data so as to be offset by processing units whose number corresponds to the parameter, other sorting methods may be employed. 
   8. Applications 
   All the copy protection methods described above are not necessarily used at the same time. By using one of them, a combination of some of them, or all of them, copy protection can be achieved even when the HDD  10  is changed. 
   The mapping and the inverse mapping programs, which are used in the foregoing examples, may be stored not only in the ROM  6  but also in the flash RAM  7 . Furthermore, the mapping and the inverse mapping programs may employ different methods for each example or may employ the same methods for each example. 
   In the above examples, the case in which music data is stored in the HDD  10  of the music server is described. However, the present invention can be applied in the same manner to cases in which data such as still images, moving images, or text data are stored in the storage unit of another digital apparatus. This enables protection of copyrighted data to be achieved even when the storage unit is changed. Particularly, in the method in which the parameter pointing to the entry cluster number of a file is transformed using a mapping intrinsic to the apparatus, since this method uses the FAT entry number of the common DOS file format, the present invention can be easily implemented in a common apparatus using the DOS file format.