A copy prevention method and apparatus for a digital video system is disclosed including the steps of: (a) adding a header area of a header start code and key field to a reproduced bit stream; (b) decrypting and transmitting the bit stream to which the header area is added; (c) detecting a key held of the decrypted and transmitted bit stream and detecting copy prevention information; and (d) encrypting the bit stream according to information detected from stop (c) and recording it an tape.
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0. 52. A recording medium to be read by a copy protection apparatus, the recording medium comprising:
a key information area for storing key information, said key information for operatively controlling a decryption of encrypted digital content; and
a data area including encrypted digital content, wherein said data area comprises a plurality of first data segments, each first data segment includes a plurality of second data segments, each second data segment comprises a header portion and a data portion, wherein at least the encrypted digital content is recorded in the respective data portions, and the header portion includes copy prevention information for indicating whether or not a copy of the encrypted digital content is permitted and an identifier for identifying a presence or a location of the copy prevention information.
0. 36. A recording medium to be read by a copy protection apparatus, the recording medium comprising:
a data area including encrypted digital content;
a copy prevention information area for storing copy prevention information, which indicates whether or not a copy of the encrypted digital content is permitted; and
a key information area for storing key information, said key information for operatively controlling a decryption of the encrypted digital content,
wherein said copy prevention information area further includes an identifier to identify an existence or a location of the copy prevention information,
wherein said data area includes a plurality of first data segments, each first data segment includes a plurality of second data segments, and each second data segment comprises a header portion and a data portion, and
wherein at least the encrypted digital content is recorded in the respective data portions.
0. 35. A copy protection method for a copy protection apparatus including a generating device and a recording device, the copy protection method comprising:
providing, via the generating device, encrypted key information, encrypted digital content, an identifier and copy prevention information, the encrypted digital content being encrypted by the encrypted key information, the encrypted key information required for at least decryption of the encrypted digital content, the identifier identifying an existence or a location of the copy prevention information and the copy prevention information indicating whether or not copying of the encrypted digital content is permitted, wherein the encrypted digital content is partitioned into one or more gop (Group Of Picture); and
recording, via the recording device, the encrypted key information, the encrypted digital content of gops, the identifier and the copy prevention information on a digital recording medium,
wherein the copy prevention information and the identifier are recorded in an area followed by the gops.
0. 32. A copy protection method for a copy protection apparatus including a generating device and a recording device, the copy protection method comprising:
providing, via the generating device, encrypted key information, encrypted digital content, an identifier and copy prevention information, the encrypted digital content being encrypted by the encrypted key information, the encrypted key information required for at least decryption of the encrypted digital content, the identifier identifying an existence or a location of the copy prevention information and the copy prevention information indicating whether or not copying of the encrypted digital content is permitted, wherein the encrypted digital content is partitioned into a plurality of data segments, each of which includes a header portion and a data portion respectively, and wherein the copy prevention information and the identifier are included in the header portion followed by the data portion, and the encrypted digital content is included in the respective data portions; and
recording, via the recording device, the encrypted key information, and the plurality of data segments on a digital recording medium.
0. 1. A copy prevention method for a digital video system comprising the steps of:
(a) receiving a digital data stream reproduced from a digital medium;
(b) detecting an encryption key, which is a portion of said received digital data stream;
(c) decrypting said encryption key using key information;
(d) decrypting said received digital data stream based on said decrypted encryption key; and
(e) transmitting said decrypted digital data stream to at least one of a monitor and a digital recorder.
0. 2. A copy prevention method for a digital video system as claimed in
0. 3. A copy prevention method for a digital video system as claimed in
0. 4. A copy prevention apparatus for a digital video system comprising:
receiving means for receiving a digital data stream reproduced from a digital medium;
a key detector to detect an encryption key, which is a portion of said received digital data stream;
a decryption unit to decrypt said encryption key using key information and to decrypt said received digital data stream based on said decrypted encryption key; and
a controller to control transmission of said decrypted digital data stream to at least one of a monitor and a digital recorder.
0. 5. A copy prevention apparatus for a digital video system as claimed in
0. 6. A copy prevention apparatus for a digital video system as claimed in
0. 7. A copy prevention method for a digital video system comprising the steps of:
(a) receiving a digital data stream reproduced from a digital medium;
(b) detecting an encryption key, which is a portion of said received digital data stream;
(c) decrypting said encryption key using key information;
(d) decrypting said received digital data stream based on said decrypted encryption key.
0. 8. A copy prevention method for a digital video system as claimed in
0. 9. A copy prevention method for a digital video system as claimed in
0. 10. A copy prevention apparatus for a digital video system comprising:
receiving means for receiving a digital data stream reproduced from a digital medium;
a key detector to detect an encryption key, which is a portion of said received digital data stream;
a decryption unit to decrypt said encryption key using key information and to decrypt said received digital data stream based on said decrypted encryption key.
0. 11. A copy prevention apparatus for a digital video system as claimed in
0. 12. A copy prevention apparatus for a digital video system as claimed in
0. 13. A copy prevention method for a digital video system comprising the steps of:
(a) receiving a digital data stream reproduced from a digital medium;
(b) detecting an encryption key, which is a portion of said received digital data stream;
(c) decrypting said encryption key using predetermined key information;
(d) decrypting said received digital data stream based on said decrypted encryption key.
0. 14. A copy prevention method for a digital video system as claimed in
0. 15. A copy prevention apparatus for a digital video system comprising:
receiving means for receiving a digital data stream reproduced from a digital medium;
a key detector to detect an encryption key, which is a portion of said received digital data stream;
a decryption unit to decrypt said encryption key using predetermined key information and to decrypt said received digital data stream based on said decrypted encryption key.
0. 16. A copy prevention apparatus for a digital video system as claimed in
0. 17. A copy prevention method for a digital data system, comprising the steps of:
(a) receiving first key information;
(b) encrypting second key information using said first key information;
(c) encrypting digital data streams using said second key information; and
(d) recording at least said encrypted second key information and said encrypted digital data streams on a digital medium.
0. 18. The method of
0. 19. The method of
0. 20. A copy prevention apparatus for a digital data system, comprising the steps of:
an encryption unit receiving first key information, encrypting second key information using said first key information, and encrypting digital data streams using said second key information; and
a controller controlling recording of at least said encrypted second key information and said encrypted digital data streams on a digital medium.
0. 21. The apparatus of
0. 22. The apparatus of
0. 23. A recording medium having a data structure for controlling operation of copy prevention function in a digital data processing device, comprising:
a digital data area storing digital data encrypted using first key information; and
a key information area storing said first key information encrypted using second key information, said first key information operatively controlling the decryption of said encrypted digital data in a digital data process device.
0. 24. A copy prevention method for a digital data system, comprising:
receiving first key information, said first key information for encrypting digital data;
encrypting said first key information using second information; and
transferring said encrypted first key information.
0. 25. The method of
0. 26. The method of
0. 27. The method of
0. 28. A copy prevention apparatus for a digital data system, comprising:
an encryption unit receiving first key information, said first key information for encrypting digital data, and encrypting said first key information using second key information; and
a controller controlling a transfer of said encrypted first key information.
0. 29. The apparatus of
0. 30. The apparatus of
0. 31. The apparatus of
0. 33. The method of claim 32, wherein the copy prevention information is updated prior to said recording step, and wherein said recording step records the encrypted digital content only when the copy prevention information before the update indicates that a copy of the encrypted digital content is permitted.
0. 34. The method of claim 32, wherein said recording step includes recording the encrypted key information in a control area followed by an area for recording the encrypted digital content.
0. 37. The recording medium of claim 36, wherein said key information area is followed by said data area.
0. 38. The recording medium of claim 36, wherein the encrypted digital content is encrypted in packets and the packets correspond to the second data segments.
0. 39. The recording medium of claim 36, wherein the key information is recorded in an encrypted format.
0. 40. The recording medium of claim 36, wherein the copy prevention information is updated to indicate that a copy of the encrypted digital content has been made.
0. 41. The recording medium of claim 40, wherein the updated copy prevention information indicates that no more copies of the encrypted digital content are permitted.
0. 42. The recording medium of claim 36, wherein the header portion includes classification information to classify the encrypted digital content recorded in the data portion.
0. 43. The recording medium of claim 36, wherein said copy prevention information area is followed by said data area or, is included in the header portion.
0. 44. The recording medium of claim 43, wherein said copy prevention information area further includes an identifier to identify that the copy control information is included.
0. 45. The method of claim 32, wherein the copy prevention information is variably placed within the header portion.
0. 46. The recording medium of claim 43, wherein the copy prevention information is written in various locations within the header portion.
0. 47. The recording medium of claim 36, wherein the header portion is not an encrypted portion while the data portion is an encrypted portion.
0. 48. The method of claim 32, wherein the header portion is not an encrypted portion while the data portion is an encrypted portion.
0. 49. The method of claim 35, wherein the copy prevention information is updated prior to said recording step, and wherein said recording step records the encrypted digital content only when the copy prevention information indicates that a copy of the encrypted digital content is permitted.
0. 50. The method of claim 35, wherein said recording step includes recording the encrypted key information in a control area followed by an area for recording the encrypted digital content.
0. 51. The method of claim 35, wherein the area followed by the gops is not encrypted while the gops is an encrypted portion.
0. 53. The recording medium of claim 52, wherein said key information area is followed by said data area.
0. 54. The recording medium of claim 52, wherein said encrypted digital content is encrypted in packets and the packets correspond to the second data segments.
0. 55. The recording medium of claim 52, wherein the key information is recorded in an encrypted format.
0. 56. The recording medium of claim 52, wherein the copy prevention information is updated to indicate that a copy of the encrypted digital content has been made.
0. 57. The recording medium of claim 56, wherein the updated copy prevention information indicates that no more copies of the encrypted digital content are permitted.
0. 58. The recording medium of claim 52, wherein the header portion further includes classification information to classify the encrypted digital content recorded in the data portion.
0. 59. The recording medium of claim 52, wherein the header portion is not an encrypted portion while the data portion is an encrypted portion.
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to respect6 5 comprises a PES header detecting portion 10 for searching the parallel data in synchronization with a clock clk to detect the PES header, and a copy prevention information extractor 20 enabled by the PES header signal of PES header detecting portion 10 to detect the copy prevention information field.
Referring to
As shown in
The operation and effect of the present invention will be explained below. Generally, in case of reproducing or copy recording data on tapa tape, connections between systems are made as shown in
With those connections, an MPEG bit stream reproduced from VCR A is input to a satellite receiver or high-definition TV so that it cannot be recognized whether the stream is displayed on a screen or input to VCR B and recorded on another video tape.
For this reason, according to the present invention, in case that the bit stream reproduced from VCR A is copied from VCR B, information on copy prevention is transmitted to VCR B from VCR A. VCR B analyzes this information which is recorded with the bit stream.
Here, the insertion position of the copy prevention information contained in a GA bit stream is very limited because it must not affect decoding of the decoder of the satellite receiver or high-definition TV so that an image is displayed normally on a monitor. The copy prevention information may be inserted into the front end of the MPEG bit stream or inside the PES header.
When the MPEG bit stream is decoded in units or of group of picture (GOP), the respective GOPs are classified by their cop GOP start codes. This is useful in transmitting initialization data to a recording-side VCR because decoding is never affected even when a slight amount of data is added to the front end of the MPEG bit stream.
The case of inserting the copy prevention information into the PES header is useful in repeated transmission of information because copy prevention of a recording medium such as DSM is decided using CR and OC flaps of the PES header and additional copy information field. In this case, there are a variety of copy preventing methods.
First, when a mode of “No Copy” is detected from the additional copy information field of the PES header, VCR B is not able to enter its recording mode.
Second, when a mode of “Copy Permitted” is detected in order to implement a copy prevention such as DAT mode, VCR B records but “No Copy” mode is recorded in the additional copy information field to interrupt recopying from a copying tape. This means that a secondary source tape can be made, but a third source tape cannot.
Third, for “Back-up Copy”, tape B copied from VCR B is reproducible normally only in VCR A. According to this method, reproducing-side VCR A encrypts the bit stream with its own inherent key and records it on tape so that only reproducing-side VCR A decrypts the MPEG bit stream recording on the tape. For every VCR set, a unique key is provided, encrypted by VCR's key and recorded on tape B. However, the VCR set for recording tape B is VCR B and tape B is encrypted by VCR A's key so that VCR A's key needs to be transmitted to VCR B with GA bit stream.
Accordingly, when the key information of VCR A is transmitted as a header in advance prior to the bit stream in the “Back-up Copy”, it is recorded at the front end of tape B, which satisfies the insertion position of the copy prevention information mentioned before.
Here, as shown in
In case of recording the bit stream shown in
Here, a header area added to the front of the MPEG bit stream is formed with a tape header start code, that is, the header identifier code, and a key field for storing key information. In case of encrypting the MPEG bit stream in units of GOP, encryption blocks are classified by the packet start code prefix and stream ID of the PES header. The encryption block is a basic unit of encryption and can change whether encryption is performed in units of the encryption block, and encryption algorithm and key selection. Here, the encryption blocks must not be encrypted until the additional copy information field of the PES header. Encryption is performed until the end of the encryption block after the additional copy information field. The first ‘transmission header’ is not encrypted.
The operation of performing the “back-up Copy” mode by adding the header will be described below.
First, in copying, when recording data of tape A is encrypted, reproducing-side VCR A decrypts it using the key information of the key field so as to make message m. Its key information is added to the header and transmitted in the format of
Recording-side VCR B records the key information transmitted from reproducing-side VCR A on the header of copying tape B and then records the encrypted bit stream. Here, when the key information is transmitted from reproducing side to recording side, for security, a public-key encryption may be employed to the system because the information may be exposed to a pirate.
Such public-key encryption system ensures the secret of data even though the public-key is exposed but cannot be processed in real-time due to a great amount of calculation. Therefore, this system is not improper when the MPEG bit stream is encrypted directly. The “Back-up Copy” can be implemented when the MPEG bit stream is encrypted using a block-cipher algorithm or stream-cipher algorithm such as DES and a key used is encrypted in the public-key encryption.
In this case, every VCR u incorporates encryption algorithm EPKU corresponding to the public-key and decryption algorithm DPKU corresponding to the secret key. Encryption algorithm EPKU takes a power key of VCR u, and decryption algorithm DPKU an internal key of VCR u.
Here, the internal key may be opened to the public. Reproducing-side VCR A transmits the internal key on the key field of the header because another VCR encrypts using the internal key. Recording-side VCR B randomly selects a key Y used in the block-cipher algorithm such as DES and encrypts it with the public-key encryption system using an external key EPKA. The result is recorded on the key field of copying tape B.
Sequentially, the data is divided into encryption blocks and encrypted and recorded in the block-cipher algorithm using key Y. In this method, the bit stream of
When copying tape B is reproduced in reproducing-side VCR A, key Y can be restored by decryption DPKA[EPKA (Y)] in which data is decrypted properly. In other VCRs, key Y cannot be found, which disables the decryption of the bit stream.
As An embodiment of the present invention, shown in
When playback starts for tape copying, reproducing portion 1 detects data recorded on tape as shown in
When the bit stream of
Copying prevention information detecting portion 5 searches the PES header area to detect the additional copy information field. Here, though a slight amount of information is recorded in the additional copy information field, redundancy is provided in several areas of the bit stream to increase reliability of information transmitted.
Copy prevention information detecting portion 5 extracts the value of AC flag from the PES header flag in order to calculate the position of the additional copy information field because it varies within the PES header. Here, when copy prevention information correcting portion 6 corrects the output of copy prevention information detecting portion 5, encrypting portion 7 performs encryption using the block-cipher algorithm such as DES. Here, copy prevention information correcting portion 6 performs correction while the input data is stored in a RAM. Accordingly, encrypting portion 7 records the encrypted bit stream on tape in recording portion 8. Because the key information of the reproducing-side VCR is added on the copying tape, only a VCR having this key information can reproduce tape normally.
As shown in
PES header detector 10 for detecting the PES header is formed as shown in
Here, packet start code detecting portion 13 searches the bit stream shown in
Meanwhile, stream ID code detector 14 searches the output of second flipflop 12 and detects the stream ID area of the PES header. Then, detection signal is-sid shown in
Here, copy prevention information extractor 20 for detecting the copy prevention information is formed as shown in
D-flipflop 23 is synchronized to the CR flag or the output of D-flipflop 21 shown in
Copy prevention position detector 25 searches the PD, TM and AC flags of the parallel data of PES header detector 10 shown in
D-flipflop 27 synchronized to HIGH output rco of counter 26 holds the additional copy information field from the parallel data of D-flipflop 21 shown in
As described above, in the copy prevention method and apparatus for a digital video system of the present invention, a key information is recorded with a bit stream so that a VCR having the key information reproduces tape normally, thereby preventing illegal copy of tape. In addition, for key information transmission, the public-key encryption is introduced to disable a pirate to release the copy prevention, increasing reliability of copy prevention.
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