Data record media

Abstract: An optical disk (D) has a first record layer (L 1 ) and a second record layer (L 2 ) having two recording formats. Encrypted data is recorded on the first record layer (L 1 ). Encrypting key data is recorded on the second record layer (L 2 ). The encrypting key data is used for decoding the encrypted data. This recording technique makes easy reproduction of the recorded data quite difficult. If data recorded on a bit-formed portion can be reproduced by any means, the data signal recorded on the optical disk cannot easily be reproduced.

Description: This invention relates to media for recording data, recording data on data record (recording, recordable, or recorded) media, and reproducing data from data record media. Of data record media for recording a data signal such as audio data, video data or various kinds of data, a medium for optically recording such a data signal has been made popular worldwide. The optical record medium may comprise a so-called compact disk for music or a CD-ROM that is a version converted from the CD for music into a CD for data. Concurrently with the worldwide prevalence of the CD and the CD-ROM, lots of pirated editions of original media are likely to be floating around the world. Of these pirated editions, some malignant editions have been found. For example, a malignant edition is created to strip a protective layer off a compact disk so that an aluminium layer (that is, the layer on where pits are formed) may be exposed out, coat a plating layer on the aluminium layer, and repetitively stamp the plated layer for reproducing many duplications. It is quite difficult to defend the original edition against this kind of malignant one. EP-A2-0 426 409 discloses a multi-layered optical disk comprising a plurality of recording layers accumulated in the thickness direction wherein a light beam is focussed on one of the tracks of one of the layers thereby to record and reproduce data, the optical disk being characterized in that recording layers each have an identification section storing an address of the recording layer which the identification section belongs to. EP-A1-0 634 741 discloses a recording medium, a method of controlling same, and system utilizing electronic publications. An optical disk is divided into a plurality of sections at least one of which is made a section (formatted in MS-DOS, for example) having a format different from the logical format of a CD-ROM. Publication data is optically recorded in at least one section of the sections other than the first section in accordance with the CD-ROM logical format. A CD-ROM utilization tool that utilizes publication data in the CD-ROM logical format and a CD-ROM emulator for converting a request for access to the CD-ROM logical section issued by the CD-ROM utilization tool to a request for access to the optical disk are recorded in the first section. As a result, publication data, in accordance with a CD-ROM logical format, accumulated in the realm of CD-ROM electronic publications, a tool for creating and converting this data and a CD-ROM utilization tool can be put to use without being wasted. As a method for preventing illegal copying of an original compact disk, as disclosed in Japanese Patent Application Publication No. JP-A-95-182 776, a method has been proposed for recording on the compact disk secret data disabled to copy. This method is not so effective for the above indicated physical illegal copy. Moreover, the aforementioned problem is quite serious in a digital video disk (DVD), that is a so-called next-generation data record medium. Respective different aspects of the invention are set forth in the respective independent claims hereof. According to an embodiment of the invention, encrypted data to be originally recorded and key data for solving the encryption are recorded on corresponding recording areas whose recording formats or layers are different from each other. Or, the content data is recorded over at least two recording areas whose recording formats or layers are different from each other. This method inhibits easy reproduction of the original data or makes it difficult to reproduce the data recorded on an area even if the data recorded on the other area can be reproduced by any means. Hence, this method inhibits easy obtaining of the final data (reproduced data). A data record medium according to an embodiment of the invention includes at least two recording areas having the corresponding recording formats or layers. To solve the above-indicated problem, the encrypted data is recorded on one recording area and at least part of key data for solving the encryption of the encrypted data is recorded on the other area. Or, the content data is recorded over at least two recording areas. Further, according to another example there is provided a method for recording data on a data record medium having at least two recording areas whose recording formats or layers are different from each other. On one recording area, encrypted content data is recorded. On the other recording area, at least part of key data for solving the encryption of the encrypted data is recorded. Or, the content data is recorded over at least two recording areas. Further, according to yet a further example there is provided a method for reproducing data from a data record medium having at least two recording areas whose recording formats or layers are different from each other. To solve the above-indicated problem, this method takes the steps of reading the data recorded over at least two recording areas out thereof and synthesizing the data read from the areas with each other. In operation, encrypted data and key data for solving the encryption of the encrypted data may be recorded on corresponding recording areas of at least two areas whose recording format or layers are different from each other. Or, the content data to be recorded may extend over at least two recording areas whose recording formats or layers are different from each other. For example, even if the content of the data recorded on one recording area can be reproduced by any means, the difficulty of reproduction of the data recorded on the other area makes it impossible to obtain the final data (reproduced data). According to an embodiment of the present invention there is provided a medium for recording data, a method for recording data, a method for recovering data, an apparatus for recording data and an apparatus for recovering data which are arranged to inhibit easy reproduction of a recorded data signal even it a pit-formed layer of the data record medium can be reproduced by any means. According to a first aspect of the present invention there is provided a medium for recording data comprising at least two working areas operable to record data, wherein at least one of said working areas contains encrypted data and a table of contents recorded in a first recording format by stamping and at least one other of said working areas contains at least part of a key recorded with a second recording format different from said first recording format, said at least part of a key to be read out based on said table of contents and to be used for decoding said encrypted data, wherein copying by stamping of data recorded in said at least one other of said working areas is inhibited. According to a second aspect of the present invention there is provided a method for recording data on a medium having at least two working areas operable to record data, comprising the steps of: recording encrypted data and a table of contents in a first recording format by stamping in at least one working area; and recording at least part of a key with a second recording format different from said first recording format, said at least part of a key to be read out based on said table of contents and to be used for decoding said encrypted data in at least one other working area, wherein copying by stamping of data recorded in said at least one other working area is inhibited. According to a third aspect of the present invention there is provided a method for recovering data from a medium having at least two working areas operable to record data, comprising the steps of: reading a table of contents recorded in a first recording format by stamping from at least one working area; reading at least part of a key based on said table of contents, said at least part of a key being recorded in a second recording format different from said first recording format and being used for decoding encrypted data from at least one other working area, wherein reproduction of data recorded in said at least one other working area is inhibited; reading encrypted data recorded in said first recording format by stamping from said at least one working area; and decoding said encrypted data by using said key. According to a fourth aspect of the present invention there is provided an apparatus for recording data on a medium having at least two working areas operable to record data, comprising: means for recording encrypted data and a table of contents in a first recording format by stamping in at least one working area; and means for recording at least part of a key with a second recording format different from said first recording format, said at least part of a key to be read out based on said table of contents and to be used for decoding said encrypted data in at least one other working area, wherein copying by stamping of data recorded in said at least one other working area is inhibited. According to a fifth aspect of the present invention there is provided an apparatus for recovering data from a medium having at least two working areas operable to record data, comprising: means for reading a table of contents and encrypted data recorded in a first recording format by stamping from at least one working area; and means for reading at least part of a key based on said table of contents, said at least part of a key being recorded in a second recording format different from said first recording format and being used for decoding said encrypted data from at least one other working area, wherein reproduction of data recorded in said at least one other working area is inhibited; and means for decoding said encrypted data by using said key. The invention will now be further described, by way of illustrative and non-limiting example, with reference to the accompanying drawings, in which: Fig. 1 is an explanatory view showing encrypted data, encrypting key data and an optical disk for recording them according to an embodiment of the invention; Fig. 2 is an explanatory view showing an arrangement of reading the encrypted data and the encrypting key data from an optical disk and decoding the encrypted data according to an embodiment of the invention; Fig. 3 is a flowchart showing a flow of data from an optical disk to a reproducing process according to an embodiment of the invention; Fig. 4 is an explanatory view showing an arrangement of an optical disk according to an embodiment of the invention; Fig. 5 is an explanatory view showing a format of recording content data over first and second record layers; and Fig. 6 is a circuit diagram showing a schematic arrangement of a reproducing apparatus for reproducing the optical disk according to the embodiment of the invention. Preferred embodiments of the invention will now be described with reference to the drawings. At first, the description will be oriented towards the use of an optical disk having two record layers with corresponding recording formats as a data record (recording, recordable or recorded) medium. In this embodiment, an optical disk D is, as shown in Fig. 1, formed to have a base plate B, first and second record layers L 1 and L 2 laminated on the plate B in sequence, and a transparent protective layer P formed on the top of the record layers. As an example, encrypted data is recorded on the first record layer L 1 . Key data (called "encrypting key data") for solving encryption (called "decoding") of the encrypted data is recorded on the second record layer L 2 . The encrypted data to be recorded on the first record layer 1 1 of the optical disk D is content data (that is, data to be recorded) encrypted on the encrypting key data by an encrypting circuit 3. Also, the encrypted data and the encrypting key data are provided a record unit 5 such as light pickup device. Thereafter, each of the encrypted data and the encrypting key data is recorded an each of the first record layer L 1 and the second record layer L 2 by changing a focus of the light pickup device. Further, the information indicating whether or not the encrypting key data is recorded on the second recording layer L 2 of the optical disk D is recorded on TOC (table of contents) of the first record layer L 1 of the optical disk D. TOC area is described in detail later. On the other hand, when reproducing the optical disk D, as shown in Fig. 2, the encrypted data recorded on the first record layer L 1 and the encrypting key data recorded on the second record layer L 2 are read out of the optical disk D by a reproduce unit such as a light pickup device, by changing a focus of the light pickup device. The read data are sent to a decoding circuit 4, in which the encrypted data is decoded on the encrypting key data. The decoded data is the content data reproduced from the optical disk D. More concretely, the decoding circuit 4 operates to generate the decoding key data based on the encrypting key data and decode the encrypted data based on this decoding key data. In addition, Figs. 1 and 2 show plural record layers laminated on one side of the optical disk D. The record layers may be laminated on both sides of the optical disk D. The flow of processes in reproducing the data from the optical disk D will be shown in Fig. 3. The optical disk D, as shown in Fig. 4, includes a center hole 102 in the center of the disk, a lead-in area 103 corresponding to a TOC (table of contents) area served as a program-managing area, a data area 104 for recording data, and a lead-out area 105 corresponding to the data termination area ranged in the describing sequence from the inner periphery to the outer one. As an example, on the TOC area located at the innermost periphery of the first record layer L 1 of the optical disk D recorded is the information indicating whether or not the encrypting key data is recorded on the second record layer L 2 . As shown in Fig. 3, at a step S1, a process is executed to read the information recorded on the TOC area of the first record layer L 1 , that is, the first later of the optical disk D. Then, at a step S2, based on the information recorded on the TOC area, it is determined whether or not the encrypting key data is recorded on the second layer of the optical disk D, that is, the second record layer L 2 . If not at the step S2, the operation goes to a step S6. If no encrypting key data is determined to be recorded at the step S2, it means that the data recorded on the first record layer L 1 is data that is not encrypted. Hence, at the step S8, the data is road out of the first record layer L 1 as it is. On the contrary, if, at the step S2, the encrypting key information is determined to be recorded on the second record layer L 2 , the operation goes to a step S3. At the step S3, the encrypting key data is read out of the second record layer L 2 . At a next step S4, the encrypted data is read out of the first record layer L 1 . At a next step S5, based on the encrypting key data read out of the second record layer L 2 , the encrypted data read out of the first record layer L 1 is decoded. As mentioned above, according to this embodiment, the encrypted data is recorded on the first record layer L 1 of the optical disk D. The encrypting key data is recorded on the second record layer L 2 that is different from the first record layer L 1 . Even if, therefore, a pirated edition of the original disk may be created by stripping the protective layer P and the like off the first record layer L 1 for exposing out the layer L 2 , coating a layer like a plating one on the first record layer L 1 , the reproduction of the encrypting key data recorded on the second record layer L 2 is not made so easy. Also, it is difficult to strip the first record layer L 1 from the second record layer L 2 of the optical disk D. On the optical disk D of this embodiment, hence, the original data is disallowed to be reproduced from the encrypted data recorded on the first record layer L 1 . In the foregoing embodiment, the description will be oriented to the optical disk D having the first and the second record layers L 1 and L 2 for the two recording formats. In addition, the recording areas for these two recording formats may be a combination of a magneto-optical recording area and a pit type recording area, a combination of a phase variable recording area and the pit type recording area, a combination of an organic coloring matter type recording area and the pit type recording area, or a record medium for recording data with an ultraviolet laser beam and the pit type recording area. In these combinations, the encrypted data is recorded on the pit type recording area and the encrypting key data is recorded on the magneto-optical recording area, the phase variable type one, the organic coloring matter type one, or the record medium for recording data with the ultraviolet laser beam. Moreover, as another combination of the record mediums for the two recording formats, it is possible to select a combination of a recording area whose groups are made variable on the disk, that is, a so-called wobbling type recording area and one of the above-mentioned recording areas such as the pit type one, the magneto-optical one, the phase variable type one, and the organic coloring matter type one. In this combination, for example, the encrypting key data may be recorded on the wobbling type recording area. As described above, if one of the two recording areas is the pit type area the data of which may be more easily reproduced than the other type areas, the other recording area may be the magneto-optical area, the phase variable type area, the organic coloring matter type area, or the area for recording data with the ultraviolet laser beam, from each of which the recorded data is difficult to be reproduced. In this combination, for example, even if a pirated edition of the original disk can be created by stripping the protective layer P off the recording area for exposing out the recording area and coating a plating layer on the pit type recording area, it is quite difficult to reproduce the other recording area. It means that no original data is allowed to be reproduced from the optical disk. The above-indicated data recording with an ultraviolet laser beam is operated as follows: A suitable ultraviolet laser beam to working a material of the optical disk is applied to a plate of the optical disk composed of polycarbonate or acrylic. An ablation takes place on the portion on which the ultraviolet laser beam spot hits. The ablation results in eroding the hit portions and thereby forming pits on the plate. Hence, the data recording area with the ultraviolet laser beam may be formed on a portion except the pit-formed recording area for the content data. As indicated above, since the encrypting key data may be formed on the portion except the original recording area, the duplication of the data is made substantially impossible. Further, the polycabonate serves to absorb a ray having a wavelength of about 280 nm or less. The acrylic serves to absorb a ray having a wavelength of about 360 nm or less. The ultraviolet laser beam having a wavelength of 190 nm or less is absorbed by the air. In light of these properties, for decomposing the plate of the optical disk through light, the ultraviolet laser beam is recommended to have a wavelength of 190 to 370 nm. In the foregoing embodiments, the overall encrypting key data is not necessarily recorded on the optical disk. It is possible that, e.g., only part of the encrypting key data is recorded and the remaining part may be entered from an external input unit. Next, the pair of recording formats include pit-forming as one recording format and marking on the disk with a high-output laser as the other format. In this pair, the encrypted data is recorded on the pit-forming type recording area, while the encrypting key data composed of alphanumeric codes (so-called SID codes), for example, is marked on the inner peripheral portion of the optical disk by applying the high-output laser onto the optical disk. If the data disallowed to be read by a light pickup device is used as the encrypting key data, the encrypting key data composed of alphanumeric codes is entered into the optical disk reproducing apparatus through the effect of an external input unit such as a keyboard. The optical disk reproducing apparatus operates to decode the encrypted data based on the encrypting key data entered from the external input unit. In the above-indicated case, even if the data recorded on the pit-formed recording area may be reproduced, no original data cannot be reproduced from the optical disk only unless the encrypting key data composed of alphanumeric codes is entered from the external input unit. In case the optical disk D contains the foregoing first and the second record layers L 1 and L 2 as the recording areas for the two recording formats, as shown in Fig. 5, the data is recorded alternately on the first and the second record layers L 1 and L 2 for preventing the incorrect duplication of the data. That is, in the case of the recording as shown in Fig. 5, if an pirated edition of the original disk may be created by stripping the protecting layer P off the first record layer L 1 for exposing out the layer L 1 , the reproduction of the data recorded on the layer L 2 is made substantially impossible. Hence, the data recorded on the optical disk D is disallowed to be reproduced. It means that the pirated edition of the original disk cannot be simply created. The data to be recorded alternately on the first and the second record layer L 1 and L 2 may be recorded every 1 bit or every several bits greater than 1 bit. The data recorded alternately on the first and the second record layers L 1 and L 2 are not necessarily encrypted. When reproducing the data from the optical disk, the operation is executed to read the data recorded alternately on the first and the second record layers L 1 and L 2 and combine the data recorded on the first layer L 1 and the data recorded on the second layer L 2 with each other for composing the original data. Whether or not the optical disk employs the recording format as shown in Fig. 5 is determined by recording on the TOC area of the first layer L 1 the information indicating the use of the recording format as shown in Fig. 5 in the same way as the first embodiment. When reproducing the data from the optical disk, the data recorded over the first and the second layers L 1 and L 2 are read out according to the information recorded on the TOC area. Then, the data recorded on the first layer L 1 and the data recorded on the second layer L 2 are combined with each other for composing the original data. The alternate reproduction of the data from the first and the second layers L 1 and L 2 is made quite difficult in light of the performance of the current light pickup device. In actual, hence, the reproducing operation is executed to read a piece of data recorded on the first layer L 1 by a predetermined length (for example, one sector), store the piece of data in memory, read a piece of data recorded on the second layer L 2 by a predetermined length (for example, one sector), store the piece of data in memory, and alternately read the data stored in these memories, and synthesize both pieces of data with each other, for reproducing the original data. The combination of the encrypted data and the encrypting key data may be defined on each file for example, program data. In this case, however, it is necessary to record the identifying information for each file. This variation of the combination of both data at each file makes it possible to enhance the effect in preventing the reproduction of the original data. Next, the description will be oriented to a schematic arrangement of the reproducing apparatus for reproducing the optical disk D included in the foregoing embodiments with reference to Fig. 8. At first, the description concerne with the operation executed in the case of recording the encrypted data and the encrypting key data on the optical disk D. The flow of a fundamental operation is same to the flowchart as shown in Fig 3. As shown in Fig 6, a numeral 17 denotes a light pickup device. The light pickup device 17 operates to condense a laser beam on the optical disk D, receive a reflected laser beam, read a data signal recorded on the optical disk D, and then send the data signal to the decode circuit 15. Further, the light pickup device 17 operates to send to a servo circuit 14 a focus servo error signal and a tracking error signal produced on the reflected laser beam. Under the control of the controller CPU 10, the servo circuit 14 operates to generate the focus servo error signal, a focus servo signal and a tracking error signal, the latter two of which correspond to the tracking error signal. Then, these signals are sent to the light pickup device 17. The servo circuit 14 also operates to supply a rotation servo signal for the optical disk D. The motor 18 is controlled in response to the rotation servo signal. Each of the encrypted data recorded on the first record layer L 1 and the encrypting key data recorded on the second record layer L 2 are read out of the optical disk D by changing a focus of the light pickup device. On the other hand, the decode circuit 15 operates to decode and correct an error of the data signal sent from the light pickup device 17. The encrypting key information, which has been read from the light disk D and decoded by the decode circuit 15, is stored in a working RAM 12 that is controlled by the controller CPU 10. The controller CPU 10 operates to decode the encrypted data read from the optical disk D and decoded by the decode circuit 15, based on the encrypting key data stored in the RAM 12. The program data to be used by the controller CPU 10 is stored in the program ROM 13. The original data decoded by the above process is sent to the outside through an interface circuit 16 and an output terminal 11. On the other hand, if the data is recorded over two recording areas of the optical disk D, the following operation is executed. The light pickup device 17 operates to read the data recorded over two recording areas of the optical disk D from each of the recording areas. The data read from each of the areas is decoded by the decode circuit 15 and then is stored in the working RAM 12 that is operated under the control of the controller CPU 10. That is, a piece of data recorded on the first layer L 1 by predetermined length is read out, the read data is decoded by decode circuit 15 and then is stored in the working RAM 12. Thereafter, by changing the focus of the light pickup device, other piece of data recorded on the second layer L 2 by the predetermined length is read out, the read data is decoded by decode circuit 15 and then is stored in the working RAM 12. The controller CPU 10 operates to read the data stored in the RAM 12 and the controller CPU 10 synthesize them with each other. The synthesized data results in being the content data.

Claims: A medium for recording data (D) comprising at least two working areas operable to record data , wherein at least one of said working areas contains encrypted data and a table of contents recorded in a first recording format by stamping and at least one other of said working areas contains at least part of a key recorded with a second recording format different from said first recording format, said at least part of a key to be read out based on said table of contents and to be used for decoding said encrypted data, wherein copying by stamping of data recorded in said at least one other of said working areas is inhibited. A medium for recording data as claimed in Claim 1, wherein said working areas are formed on the same disk platter layer. A medium for recording data as claimed in Claim 1, wherein said working areas are formed on different disk platter layers (L1,L2). A medium for recording data according to any preceding claim, wherein said recording formats are selected from a list including: a pit-type format; a magneto-optical format; a phase variable format; an organic coloring matter format; and an ultra-violet laser beam format. A medium for recording data according to any preceding claim, wherein data is recordable in any of said working areas independently of other of said working areas. A method for recording data on a medium (D) having at least two working areas operable to record data, comprising the steps of: recording encrypted data and a table of contents in a first recording format by stamping in at least one working area; and recording at least part of a key with a second recording format different from said first recording format, said at least part of a key to be read out based on said table of contents and to be used for decoding said encrypted data in at least one other working area, wherein copying by stamping of data recorded in said at least one other working area is inhibited. A method for recording data as claimed in Claim 6, wherein said step of recording encrypted data and said step of recording at least part of a key are performed on the same disk platter layer. A method for recording data as claimed in Claim 6, wherein said step of recording encrypted data and said step of recording at least part of a key are performed on different disk platter layers (L1,L2). A method for recording data according to any of the methods of Claims 6 to 8, wherein said recording steps are performed according to any of the methods selected from the following list: recording using a pit-type method; recording using a magneto-optical method; recording using a phase variable method; recording using an organic coloring matter method; and recording using an ultra-violet laser beam method. A method for recording data according to any of Claims 6 to 9, wherein said steps of recording data in any of said working areas are performed independently of one another. A method for recovering data from a medium (D) having at least two working areas operable to record data, comprising the steps of: reading a table of contents (S1) recorded in a first recording format by stamping from at least one working area; reading at least part of a key (S3) based on said table of contents, said at least part of a key being recorded in a second recording format different from said first recording format and being used for decoding encrypted data from at least one other working area, wherein reproduction of data recorded in said at least one other working area is inhibited; reading encrypted data (S4) recorded in said first recording format by stamping from said at least one working area; and decoding said encrypted data by using said key (S5). A method for recovering data as claimed in Claim 11, wherein said step of reading encrypted data and said step of reading at least part of a key are performed from the same disk platter layer. A method for recovering data as claimed in Claim 11, wherein said step of reading encrypted data and said step of reading at least part of a key are performed from different disk platter layers (L1,L2). A method for recovering data according to any of the methods of Claims 11 to 13, wherein said reading steps are performed according to any of the methods selected from the following list: reading using a pit-type method; reading using a magneto-optical method; reading using a phase variable method; reading using an organic coloring matter method; and reading using an ultra-violet laser beam method. A method for recovering data according to any of Claims 11 to 14, wherein said steps of reading data from any of said working areas (S3,S4) are performed independently of one another. A method for recovering data according to any of Claims 11 to 15, further comprising the steps of: entering a remaining part of said key from an external input unit if said at least part of a key is only partial; and combining said remaining part of said key with said at least part of a key to form said key. A method for recovering data according to any of Claims 11 to 16, wherein said step of reading encrypted data from said at least one working area comprises the steps of: reading any partial encrypted data recorded in at least two working areas; and combining said partial encrypted data read from said at least two working areas to form said encrypted data. An apparatus for recording data on a medium (D) having at least two working areas operable to record data, comprising: means for recording encrypted data and a table of contents in a first recording format by stamping in at least one working area; and means for recording at least part of a key with a second recording format different from said first recording format, said at least part of a key to be read out based on said table of contents and to be used for decoding said encrypted data in at least one other working area, wherein copying by stamping of data recorded in said at least one other working area is inhibited. An apparatus for recording data as claimed in Claim 18, wherein said means for recording encrypted data and said means for recording at least part of a key are operable to record on the same disk platter layer. An apparatus for recording data as claimed in Claim 18, wherein said means for recording encrypted data and said means for recording at least part of a key are operable to record on different disk platter layers (L1,L2). An apparatus for recording data according to any of Claims 18 to 20, wherein said means for recording is operable to record using any of the means selected from the following list: a pit-type recording means; a magneto-optical recording means; a phase variable recording means; an organic coloring matter recording means; and an ultra-violet laser beam recording means. An apparatus for recording data according to any of Claims 18 to 21, wherein said means for recording data in any of said working areas are operable independently of one another. An apparatus for recovering data from a medium (D) having at least two working areas operable to record data, comprising: means for reading a table of contents and encrypted data recorded in a first recording format by stamping from at least one working area; and means for reading at least part of a key based on said table of contents, said at least part of a key being recorded in a second recording format different from said first recording format and being used for decoding said encrypted data from at least one other working area, wherein reproduction of data recorded in said at least one other working area is inhibited; and means for decoding said encrypted data (4) by using said key. An apparatus for recovering data as claimed in Claim 23, wherein said means for reading encrypted data and said means for reading at least part of a key are operable to read from the same disk platter layer. An apparatus for recovering data as claimed in Claim 23, wherein said means for reading encrypted data and said means for reading at least part of a key are operable to read from different disk platter layers (L1,L2). An apparatus for recovering data according to any of Claims 23 to 25, wherein said means for reading are selected from the following list: a pit-type reading means; a magneto-optical reading means; a phase variable reading means; an organic coloring matter reading means; and an ultra-violet laser beam reading means. An apparatus for recovering data according to any of Claims 23 to 26, wherein said means for reading from any of said working areas are operable independently of one another. An apparatus for recovering data according to any of Claims 23 to 27, further comprising: means for entering a remaining part of said key from an external input unit if said at least part of a key is only partial; and means for combining said remaining part of said key with said at least part of a key to form said key. An apparatus for recovering data according to any of Claims 23 to 28, wherein said means for reading encrypted data from said at least one working area comprises: means for reading any partial encrypted data recorded in at least two working areas; and means for combining said partial encrypted data read from said at least two working areas to form said encrypted data.

Inventors: KAWASHIMA ISAO, KURIHARA AKIRA, OSAWA YOSHITOMO, OWA HIDEO, SAKO YOICHIRO, KAWASHIMA, ISAO, KURIHARA, AKIRA, OSAWA, YOSHITOMO, OWA, HIDEO, SAKO, YOICHIRO, Kawashima, Isao, Sony Corp., Kurihara, Akira, Sony Corp., Osawa, Yoshitomo, Sony Corp., Owa, Hideo, Sony Corp., Sako, Yoichiro, Sony Corp.
Applicants: SONY CORP, SONY CORPORATION
Application year: 1996
Main classification: G11B20
IPC codes: G06F1, G11B7, G11B20, G11B11, G11B19