Patent Application
20080005031
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2006-163471, filed Jun. 13, 2006, the entire contents of which are incorporated herein by reference.
1. Field
One embodiment of the invention relates to information access control using an encryption key.
More particularly, it relates to a method of generating a key for use in protection of highly confidential data.
2. Description of the Related Art
In recent years, various digital devices have been developed which access contents recorded in disc media and the like. Data recorded in a disc accessed by each of such digital devices is subjected to encryption processing to prevent an unjust access or illegal copy. When the encrypted data is recorded in a digital versatile disc (DVD), an encryption system of a content scramble system (CSS) is mainly employed.
On the other hand, as a further advanced encryption system, an advanced access content system (AACS) has been proposed (Jpn. Pat. Appln. KOKAI Publication No. 2005-39480). When this AACS system is employed, for example, a set maker obtains a specific key set from a key matrix which a licensee has, and encrypts different combinations of keys to incorporate them in individual devices.
In the AACS, each of a plurality of keys is encrypted with a device key given to each device that justly records and reproduces the contents and a randomly generated random number, and the encrypted keys are registered together with the random number in a key file and recorded in the medium. In a case where the contents are reproduced, the encrypted keys registered in the key file are decrypted with the random number and the device key of the device which is to reproduce the contents. Then, the contents are decrypted with the decrypted key to reproduce the contents.
A general architecture that implements the various feature of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention.
Various embodiments of this invention will hereinafter be described with reference to the drawings.
An access control system such as an AACS is used to protect highly confidential data.
According to information access control regarding one embodiment of this invention, a new key is generated at a time for starting one recording. This key is used to encrypt an object which is the object obtained by encoding the recording target according to a predetermined method and/or is the object of the recording target. When this object is divided during recording, the same key is used for the one recording processing.
When recording is started, a key being different to the utmost from other keys can be assigned.
When information is recorded in an information recording medium such as an optical disc, it is demanded in some case that information be encrypted and recorded. In this case, for example, contents protected by copyright are encrypted with an encryption key to form encrypted contents. Furthermore, to confidentially keep the encryption key used for the encryption, the key is encrypted with another encryption key to form the encrypted key. Moreover, the encrypted key and the encrypted contents are recorded together in a recording medium to prevent illegal copying.
At present, in digital versatile discs (DVDs) whose market has rapidly enlarged, the following countermeasure is taken to protect the copyright thereof. That is, a content scramble system (CSS) licensed by DVD copy control association (DVD CCA) is utilized for DVD videos, and a system of content protection for prerecorded media (CPPM) is utilized for DVD audios. In a copyright protection system of the contents which are recorded in the recording medium, a system of content protection for recordable media (CPRM) is utilized. The CPPM system and the CPRM system are licensed by a specific group (e.g., a group referred to as 4C Entity, LLC).
On the other hand, development of a next-generation DVD or the like with a large capacity has been advanced so that a highly definite image, a high-quality multi-channel voice signal and the like can further be recorded and reproduced. In a copyright protection system for such a case where a high-quality copyright work is recorded in such a next-generation recording medium, there is a demand for introduction of a system in which a security capability is improved more than before. As a specific example of the system, there is an advanced access content system (AACS). A control method of a contents key of the AACS which is a content protection technology employed in a high density digital versatile disc video recording (HD_DVD-VR) format will hereinafter be described.
In a conventional CPRM system, an encryption key has been generated using a media key block (MKB) and a media ID which are present in a disc to encrypt the content. On the other hand, in the AACS, the contents recorded in the disc are encrypted with the encryption keys for the respective contents without using one common encryption key.
The content protection technology employed in the HD_DVD video recording format is the AACS. The control method of the contents key in the AACS will be described with reference to
On the other hand, examples of data stored as a file in the disc 100 for use in the AACS processing include:
In the AACS, processing to generate a “title key (Kt)” for encrypting the contents is executed roughly in the following order. That is, MKB processing is performed using the lead-in MKB or the read write MKB of a newer version. The key generated by this processing is referred to as a “media key (Km)”. When this media key Km and the binding nonce are input to perform protected area key processing (Kpa processing), a “protected area key (Kpa)” is generated. This key Kpa, data of the usage rule file and data of the title key file are input to perform the title key processing (TK processing), the encrypted title key described in the title key file can be converted into an original title key Kt.
The MKB is data referred to as the media key block, and the media key Km is encrypted and recorded in the data. In the MKB, information of an unjust device is also recorded, and the unjust device cannot take out the key Km. Since the information of the unjust device is updated, a new MKB needs to be used. Therefore, the AACS of HD_DVD includes three types of MKB, that is, the lead-in MKB buried in a lead-in area of the medium, the read write MKB stored as the file in the disc and a device MKB stored in a nonvolatile memory of the device itself. It is determined that the newest MKB of these MKBs is overwritten in the read write MKB. However, when the MKB is updated to the new MKB, a value of Km is changed. Therefore, information items of all keys (Kpa, Kt, etc.) of and after the key Km are to be reproduced or re-generated.
It is to be noted that the information recording and reproducing device 200 of
The lead-in media key block (MKB) is stored in a read-only lead-in area of the medium 100, and the read write MKB is stored in a user data area which is a rewritable area. The MKB is the “media key block” in which the media key (Km) as a base key for encryption of the contents is encrypted with a set of device keys (Kd) arranged as confidential keys in the information recording and reproducing device 200 to arrange a mathematical system.
In S10 of
Here, information for generating the protected area key (Kpa) is encrypted and stored in the MKB, but additionally revoke information is also included. That is, when a security hole is arranged in a certain device key set and use of the corresponding device key Kd is prohibited by a licenser, the revoke information on the corresponding device key Kd is described. This revoke information prohibits the device having the corresponding device key Kd from decrypting a cryptograph (i.e., the revoked information cannot be reproduced). Since the information of the unjust device is successively updated with an elapse of time, the new MKB (the latest updated MKB) needs to be used. Therefore, the newer version is used as the media MKB as described above.
The media key (Km) is generated by this MKB processing. In S12 of
On the other hand, the “data based on the random number” combined with the file referred to as the binding nonce is recorded in the protected area of the top address of the title key file (TKF). This binding nonce cannot be copied with, for example, a write command of a personal computer (PC), and can be copied with an only command defined by the AACS. The information can be copied with only licensed hardware of the AACS. In consequence, outflow of the information via the PC is prevented.
Next, in S13 of
Next, title key processing for generating a title key (TK) from the key Kpa will be described. This processing is shown in S14 of
Furthermore, the media ID is recorded in a read-only burst cutting area (BCA) arranged internally from the lead-in area of the disc 100. The media ID is an inherent ID added to each medium. A media ID message authentication code (MAC) which is a tampering preventive code MAC using the media ID is stored in the user data area which is the rewritable area.
During the title key processing shown in S14 of
In a case where the generated media key is verified in S23 of
In S25 of
As described above, during the encryption and decryption of the contents, the title key and the like play significant roles. However, the title key and the like are recorded as a readable/writable file in the medium 100. Therefore, when the surface of the medium is made dirty with, for example, a fingerprint and the like, there is a possibility that the medium is easily brought into a state in which the contents cannot be read out. To solve the problem, in the AACS, the title key file (TKF) in which information such as the title key is stored is backed up.
In the title key files (TKF1 to 3), binding nonce 1 to 3 (BN1 to 3), title key file generations 1 to 3 (TKFG1 to 3), title key file nonce 1 to 3 (TKFN1 to 3) and encrypted title keys 1 to 3 (ETK1 to 3) are registered, respectively. Here, the binding nonce 1 to 3 (BN1 to 3) are random number data for use in encrypting the title key file of the device as described above. The title key file generations 1 to 3 (TKFG1 to 3) are times of changes of the title key files (TKFG1 to 3), respectively. The title key file nonce 1 to 3 (TKFN1 to 3) are random numbers for generating encrypted title keys (ETK1 to 3) of files other than the title key file of the device and the backup files.
The encrypted title keys 1 to 3 (ETK1, ETK2 and ETK3) are represented by the following equations (eq. 1) to (eq. 3):
ETK1=f(TK, BN1, TKFN3) (eq. 1);
ETK2=f(TK, BN2, TKFN1) (eq. 2); and
ETK3=f(TK, BN3, TKFN2) (eq. 3),
in which TK is a title key of a plaintext that is not encrypted, and an encryption processing function f indicates that the first parameter (TK) is subjected to the encryption processing by use of a second parameter (BN1 to 3) and a third parameter (TKFN1 to 3) as encryption keys. During encryption processing f, a known encryption algorithm such as the advanced encryption standard (AES) may be used.
That is, TKF1 is associated with TKF3, and constituted by encrypting the title key (TK) with (BN1) and (TKFN3) of the associated TKF3. Moreover, TKF2 is associated with TKF1, and constituted by encrypting the title key (TK) with (BN2) and (TKFN1) of the associated TKF1. Furthermore, TKF3 is associated with TKF2, and constituted by encrypting the title key (TK) with (BN3) and (TKFN2) of the associated TKF2.
As described above, the title key file TKF1 and the backup files TKF2 and TKF3 are associated with different files. The encrypted title keys (E-TK1, E-TK2 and E-TK3) are constituted by encrypting the title keys (TK) with (BN1, BN2 and BN3) registered in the file of the device and (TKFN1, TKFN2 and TKFN3) registered in the associated other files.
As described above, three title key files are stored and the TKFN is stored in another file. In consequence, even if one TKF is broken owing to damage on the data or the like, the broken data can be recovered from two remaining TKF data.
It is to be noted that the above-described binding nonce is data which can be read and written with an only special driving command. In consequence, unjust copying can be prevented. That is, if the TKF is copied, the accompanying binding nonce of the file is not copied. Therefore, a malicious unjust encryption/decryption action by the third party can be prevented.
It is to be noted that the associating of the title key file with the TKFN of the other backup files is not limited to the above equations (eq. 1) to (eq. 3). The title key file may be associated with the TKFN of the backup files in accordance with a pattern other than the equations (eq. 1) to (eq. 3).
The data stored in the medium for use in the recording and reproducing of the AACS will be described in detail with reference to
Management information which is information on a copy protection pointer of a video object (VOB) and/or a stream object (SOB) is stored in the user data area of the medium 100. In the user data area, the read write MKB, the encrypted title key (E-TK), the media ID MAC, the usage rule and the backup files of the block, key, code and rule are stored. Furthermore, 1998 encrypted contents at maximum can be stored in the user data area.
The contents are encrypted using one key of the 1998 title keys. However, the encrypted title keys do not have to be recorded in all of 1998 sets, and a numeric value of 0 encrypted by TK processing is described in a key which is not used. A value which increments every time this file is updated is described in the title key file generation. As described above, the title key file includes three files in total for the backup. Moreover, in a case where all of the values of the title key file generations of these three files do not agree with one another, it is meant that a certain trouble has occurred during the writing in the file.
Next, an update method of the title key file will be described. Examples of a type of the medium to which the AACS is applied include a rewritable medium and a write-once medium. In the rewritable medium, for example, every time a new content is additionally recorded, a new title key is added. Therefore, all of the title keys of the title key file need to be encrypted again by use of a new key Kpa. That is, the title key file needs to be updated.
In addition, the numeric value based on the random number of the binding nonce is described in the protected area of the title key file, but this binding nonce is used in preventing unjust cryptograph cancellation. Therefore, the binding nonce is also updated every time the title key file is updated.
On the other hand, in the write-once medium, every time the title key file is updated, the title key file is written in a new address. Therefore, the address where the binding nonce is written differs every time. However, in the AACS, it is demanded that the binding nonce be overwritten at the same place. Therefore, in the write-once medium, the title key file should not be updated. Therefore, the rewritable medium is different from the write-once medium in update conditions of the title key file.
In the title key file of
The numeric value based on the random number of the binding nonce is recorded in the protected area of the address of the medium 100 in which the title key file is written. The protected area is an area where the value can be read and written with an only special command for exclusive use in the AACS. When an element constituting the key Kpa is recorded in this portion, unjust cryptograph cancellation by use of the personal computer or the like can be prevented.
The title key of the title key file is encrypted by combining the protected area key with the binding nonce to perform the TK processing. At this time, the binding nonce of the title key file #2 is used in encrypting the title key file #1, and the binding nonce of the title key file #3 is used in encrypting the title key file #2. In consequence, even if one of three title key files is damaged, the title key file can be recovered using the two other files. The binding nonce is used in encrypting the title key in this manner. Therefore, every time the title key file is updated, the binding nonce is updated.
On the other hand, the binding nonce depends on the address in which the file is written. In a write-once medium such as HD_DVD-R, the title key file itself is stored in the new address every time. The position in which the binding nonce is written is not limited to one position. However, in the AACS, it is demanded that the binding nonce be overwritten at the same place. Therefore, in the write-once medium, the title key file is not updated.
In the title key file, 1998 title keys can be stored. It is presumed that the number of the keys agrees with each of the number of the video objects (VOB) and the number of the stream objects (SOB) and that the title key (Kt) is changed for each video object. This is because, for example, in a case where the contents are moved from the disc to another medium, if the title key being used is not deleted, a loop hole that can unjustly be copied remains. If the title key is deleted, another object that shares the same title key cannot be decrypted. Therefore, the keys which differ with the objects need to be assigned if possible. For this purpose, in the recording and reproducing device, the title key is newly generated for each recording process, and the video object and the stream object are encrypted by use of the title key.
On the other hand, especially during the recording by use of the stream object (SOB), the stream object needs to be dynamically divided in accordance with contents of digital broadcasting as a recording target. Specifically, in a case where a constituting element of the stream object (SOB) is changed, for example, the number of voice streams changes at a boundary between programs, the SOB is automatically divided at the boundary. In such a case, the title key cannot actually be switched at the boundary (if the title key is switched, much time is taken in generating the new key, and therefore during start of the recording of the divided SOB, the recording of a top portion of the SOB is missed). In such a case, the encryption by use of the same title key is successively performed.
It is to be noted that when the disc is the write-once medium (the medium which cannot be overwritten), the title key file cannot be updated. Therefore, during the processing to generate the key at the start of the recording, the title key which already exists is used.
For example, when a user turns on a power source of the information recording and reproducing device 200 to insert the rewritable medium in S40 of
Moreover, it is judged in S43 and S44 whether or not the title key file is to be updated in response to user's content recording operation, content editing operation, content deleting operation, medium discharging operation and turning-off operation of the power source of the information recording and reproducing device 200. That is, the title key file is updated only when at least one of the following three conditions is satisfied.
(1) A condition that the contents are recorded or deleted:
When the contents are recorded or deleted, the encrypted title key of the title key file is newly added or deleted. Therefore, the title key file is updated.
(2) A condition that the MKB is updated:
For example, when the version of the device MKB as the MKB held in the information recording and reproducing device 200 is newer than that of the read write MKB, the value of the device MKB is copied to the read write MKB to change the media key (Km) of the device MKB. Therefore, the title key file is updated to encrypt the title key again.
(3) A condition that only one of three title key file generations differs:
As described above, one of the three title key files is broken. Therefore, the damaged title key file is repaired (updated) using two remaining normal title key files. That is, when at least one of the above three conditions is established (S44Y), the title key file is updated (S45). When all of the above three conditions are not established (S44N), the processing is ended without updating the title key file (S46).
For example, when the user turns on the power source of the information recording and reproducing device 200 to insert the write-once medium in S50 of
Moreover, it is judged in S53 and S54 whether or not the title key file is to be written in response to the user's content recording operation, content editing operation, content deleting operation, medium discharging operation and turning-off operation of the power source of the information recording and reproducing device 200. That is, the title key file is written, when at least two conditions described below are satisfied.
(1*) A condition that the contents are recorded
(2*) A condition that any title key file is not recorded in the disc
It is demanded in the AACS that the title key file be overwritten at the same place. Therefore, when the conditions (1*) and (2*) are satisfied at the same time, the title key file is written in the write-once medium. Reasons for this will be described hereinafter.
Under the only condition (1*), every time the contents are recorded, a write request is made. This raises a problem in the write-once medium which cannot be overwritten at the same place. Under the only condition (2*), in a state in which the contents are not recorded in the disc, any valid contents key is not generated. Therefore, an only invalid encrypted title key is recorded in the title key file, and this raises a problem. In a case where both of the conditions (1*) and (2*) are satisfied, the title key file is written, when the contents are recorded in a state in which any title key file is not recorded in the disc. Therefore, the title key file is recorded in which only one valid encrypted title key is generated.
In a case where the above two conditions are both established (S54Y), the title key file is written in the disc (S55). In a case where the above two conditions are not established (S54N), the processing is ended without writing any title key file (S56).
According to the above-mentioned embodiment, each type of medium is provided with a condition on which the title key file is written. Only when the condition is satisfied, the title key file is written in the disc. According to this condition, the title key file is not uselessly updated in the rewritable medium, and the number of times when the title key file is written in the disc can be reduced. In the write-once medium, it can be prevented that the title key file with the problem is written.
The data area 112 includes areas 120, 122 in which information is recorded by a general computer and an area 121 in which audio video data (AV data) is recorded. The AV data recording area 121 includes an AV data management information area 130 including a video manager file (VMG or HDVR_MG) for managing the AV data; an ROM_video object group recording area 131 in which a file of object data is recorded according to a DVD video (ROM video) standard; a VR object group recording area 132 in which a file (a VRO file) of object data (an extended video object set: ESOBS) is recorded according to a video recording (VR) standard); and a recording area 133 in which a file (an SRO file) of stream object data (an extended stream object set: ESOBS) is recorded. An object for digital broadcasting is recorded in the SRO file. It is to be noted that the recording standard for the SRO file is appropriately referred to as a stream recording (SR) standard.
That is, in a file structure according to this embodiment, an HDVR MPEG2-TS data file, an HDVR MPEG2-PS data file and a VR MPEG2-PS data file are managed under the same route directory. For example, assuming that shortcut files linked to HR_MOVIE.VRO are title thumbnail A, C and that a shortcut file linked to VR_MOVIE.VRO is a title thumbnail B and that a shortcut file linked to HR_STRnn.SRO is a title thumbnail D, these title thumbnails A to D can be displayed in the same menu screen (see a display example of a monitor screen 52a of
Here, examples of a case where the stream is encoded in MPEG2-PS include a case where the stream is encoded in MPEG2-PS based on a DVD-VR standard (the maximum rate of 10.08 Mbps; the maximum resolution of 720×480 or 720×576); a case where the stream is encoded in MPEG2-PS at a high rate based on an HD_DVD-VR standard (the maximum rate of 30.24 Mbps; the maximum resolution of 1920×1080); and a case where the stream is encoded in MPEG2-PS at a low rate within the HD_DVD-VR standard (the maximum rate of 10.08 Mbps; the maximum resolution of 720×480 or 720×576).
The stream data encoded by (or passed through) the MPEG encoder 20 is once buffered in a high-speed memory such as a synchronous dynamic random access memory (SDRAM) 22. In this SDRAM 22, the following stream rewrite processing 1 to 3 are appropriately performed:
1. in the audio liner PCM, a value of sub_stream_id of an audio pack is rewritten;
2. contents described in RDI-PCK are rewritten; and
3. A cryptograph of CPRM is decrypted once and encrypted again in the AACS, or this may be performed in an inverted order.
The stream data buffered and processed in the SDRAM 22 is transferred to an HDD 104, an HD_DVD drive 26 or a DVD drive 28 at a predetermined timing in accordance with contents of the data. As the HDD 104, a large-capacity hard disc drive (e.g., 1 TB) is used. A blue laser (e.g., a wavelength λ=405 nm) is used in the HD_DVD drive 26, and a red laser (e.g., a wavelength λ=650 nm) is used in the DVD drive 28.
The HD_DVD drive 26 and the DVD drive 28 constitute a drive unit 24. The drive unit 24 includes two independent drives including a rotary driving system, includes an HD_DVD/DVD convertible drive (a twin pickup type) having a common rotary driving system and individual optical heads of the blue laser and the red laser, or includes a double-wavelength optical system (a single pickup type) in which the rotary driving system and the optical head have a common mechanism and the blue laser and the red laser are switched for use.
The embodiment of
The HD_DVD drive 26 copes with the recording and reproducing based on the HD_DVD-VR standard, and the DVD drive 28 copes with the recording and reproducing based on the DVD-VR standard. The DVD drive 28 is further configured to record and reproduce even the data encoded based on the HD_DVD-VR standard by use of the disc 102 of the DVD-VR standard (DVD-R/RW/RAM with one layer on one side, DVD-R with two layers on one side, DVD-RAM with one layer on each side or the like) at a constant speed or a high speed as long as the data is of MPEG-PS having the maximum rate, video attribute and the like which fall in the DVD-VR standard. (According to a specific example, it is constituted that even the data encoded based on the HD_DVD-VR standard can be copied/dubbed in the disc 102 of the DVD-VR standard at a high speed as long as the data is MPEG2-PS data of NTSC video recorded in the HDD 104 at a maximum rate of 10.08 Mbps. Needless to say, the MPEG2-PS data encoded based on this HD_DVD-VR standard can be copied/dubbed in the disc 100 of the HD_DVD-VR standard at the high speed.)
The stream data reproduced from the HD_DVD drive 26, the DVD drive 28 and/or the HDD 104 is transferred to an MPEG decoder 30 via the SDRAM 22. The MPEG decoder 30 has a function of decoding MPEG2-TS, MPEG2-PS, MPEG4-AVC or the like (e.g., a function decoding VC-1 determined according to the HD_DVD-VR standard) in response to the transferred stream. Video data (MPEG2-TS or MPEG2-PS) decoded by the MPEG decoder 30 is converted into an analog video signal having a standard or highly definite image quality by a video DAC 32 and output from a video output terminal 36. Moreover, audio data decoded by the MPEG decoder 30 is converted into an analog audio signal by an audio DAC 34, and output from an audio output terminal 38. Furthermore, when the decoded data is MPEG2-TS, the data is appropriately output from a digital output terminal 39 to the outside via an interface 37 such as IEEE1394 (or HDMI). The AV signals (the analog video signal and the analog audio signal) decoded by the MPEG decoder 30 and D/A converted by the DACs 32, 34 are input into an external monitor.
An operation of the recording and reproducing device (an HD_DVD recorder) of
In the embodiment of
It is to be noted that according to the embodiment, the VR title includes MPEG2-PS recording in which the maximum rate is suppressed at 10.08 Mbps according to the next-generation HD_DVD standard in addition to the MPEG2-PS recording according to the existing DVD-VR standard. At an object data level, it can be judged whether or not the stream data of the certain VR title is MPEG2-PS according to the DVD-VR standard or MPEG2-PS in which the maximum rate is suppressed at 10.08 Mbps according to the HD_DVD standard by judging whether described contents of specific information (e.g., the program maximum rate “program_max_rate”) of the object data is “10.08 Mbps” or “30.24 Mbps”. At a management information level, the judgment can be performed before starting reproduction of the title of the level by judging whether or not the specific information (e.g., a video attribute “V_ATR”) of the management information includes a resolution (e.g., 1280×1080) which cannot be obtained with the existing DVD-VR standard.
In the embodiment, the above-mentioned plurality of types of titles (TS title, HDVR title and VR title) are subjected to file management under the same directory as illustrated in
When one recording is started as described above, the key (the title key Kt or the contents key) for use in the encryption of the AACS is generated (ST100). This key generation processing can be performed in the same manner as in the processing described with reference to
However, when an object is to be recorded in a write-once medium such as HD_DVD-R (or HD_DVD-R:DL with two layers on one side) which cannot be overwritten, and if an encrypted object has already been recorded on a part of this medium, then the existing key (Kt) used for the encryption of the recorded object is employed for the encryption of subsequent recording processing. (Thus, the existing key is continued to use because the existing key cannot be renewed by overwriting in the write-once medium.)
In a case where the object as the recording target is not divided during recording of the object (ST102N), while encrypting the object by use of the key generated in ST100 (according to the AACS) (ST106), the encrypted object is recorded in the recording medium (the hard disc, the optical disc or a semiconductor memory) (ST108). While one recording of the object as the recording target is not ended (ST110N), the processing of ST102 to ST110 is repeated.
The object as the recording target is divided by, for example, recording pause, change of a video attribute or the like during the recording of the object (e.g., SOB of the program B) (ST102Y). In this case, when the subsequent recording is counted as another recording, the processing is not apparently one recording. However, the processing is regarded as an event during one recording, and the key (Kt) used in encrypting the object before divided (e.g., the SOB of the former half of the program B) is applied to the object after divided (e.g., the SOB of the latter half of the program B (ST104). In this case, new key generation processing (the processing described with reference to
When one recording of the object as the recording target is ended as described above (ST100Y), various pieces of management information for reproducing the recorded object is recorded in the HR_MANGR.IFO file (see
This reproduction device (corresponding to 200 of
(1) Since a key (Kt or Contents Key) being different from other keys to the utmost can be applied to an object (Video Object VOB, Stream Object SOB) at the time of start of each recording (a different key can be generated at ST100 each time the processing of
(2) Even if an object is divided, a new key is not required to be generated during recording (for instance at ST104 in
While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. For instance, according to an embodiment of the invention, not only an optical disc or a hard disk drive but also a large capacity flash-memory or the like may be used for an information medium.
Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-163471 | Jun 2006 | JP | national |
