|Publication number||USRE41074 E1|
|Application number||US 11/040,606|
|Publication date||Jan 12, 2010|
|Priority date||Nov 26, 1994|
|Also published as||CN1123226C, CN1131528A, CN1145576C, CN1150737A, CN1268126C, CN1268127C, CN1505399A, CN1516464A, CN1567993A, CN1567993B, CN1801919A, CN1822166A, CN1822167A, CN1822168A, CN1822667A, CN1822667B, CN1822668A, CN1822668B, DE69522424D1, EP0717564A2, EP0717564A3, EP0717564B1, US5761302, US6028932, US6347144, USRE39319, USRE42921, USRE42922, USRE42950, USRE42951|
|Publication number||040606, 11040606, US RE41074 E1, US RE41074E1, US-E1-RE41074, USRE41074 E1, USRE41074E1|
|Inventors||Tae Joon Park|
|Original Assignee||Lg Electronics Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (66), Non-Patent Citations (4), Referenced by (4), Classifications (22)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This is a continuation of application Ser. No. 09/053,288, filed Apr. 1, 1998, now U.S. Pat. No. 6,028,932, which is a continuation of Ser. No. 08/562,042, filed Nov. 22, 1995, now U.S. Pat. No. 5,761,302, issued Jun. 2, 1998.This is a reissue application of U.S. Pat. No. 6,347,144, which is a continuation of application Ser. No. 09/053,288, filed Apr. 1, 1998, now U.S. Pat. No. 6,028,932, which is a continuation of Ser. No. 08/562,042, filed Nov. 22, 1995, now U.S. Pat. No. 5,761,302. The contents of all these applications are incorporated by reference. The above-identified applications also claim priority to Korean Application No. 94-31373 filed on Nov. 26, 1994.
The present invention relates to a copy prevention technology for a digital video system, and more particularly, to a copy prevention method and apparatus for a digital VCR to which encryption is introduced to display a picture only in a VCR internally containing a corresponding encryption code, thereby preventing tape from being copied.
General copy prevention methods for analog VCR are presented in U.S. Pat. Nos. 4,819,098, 4,571,642 and 4,577,216.
First, U.S. Pat. NO. 4,819,098 discloses a method in which an interference signal is inserted into a video waveform in an automatic gain control circuit (AGC) of a VCR. Here, the inserted signal does not affect the AGC of its monitor but has the AGC of the VCR record an accurate level of signal on a video tape.
In U.S. Pat. No. 4,571,642 4,577,216, there is presented a method in which a phase noise or other corrected signal is inserted into the chrome chroma burst of a video waveform.
However, all the conventional technologies insert a distributing signal to an analog signal using the difference between a circuit of a monitor and a corresponding circuit of a VCR. Some VCRs may perform copy normally despite of copy prevention. Some monitors cannot display images of the original video tape. A conventional copy prevention introduced to an analog VCR system is hard to be applied to digital storage media (DSM).
Specifically, in a satellite or high-definition TV decoder, as shown in
The PES header contains a PES header flag area of 14 bits which is a field for DSM such as digital VCR, and a PES header field having a variable length. The PES header flag area includes 1-bit copyright (CR) flag, 1-bit original-or-copy (OC) flag, 2-bit PD flag, 1-bit TM flag, and 1-bit AC flag.
The PES header field varies in length, and part thereof is set by the PC PD, TM and AC flags. A PTS/DTS area is not present if the value of the PD flag is “00”. It is 40 bits if the value “10”. If the value is “11”, the area is 80 bits. A DSM trick mode field is not present if the TM flag is “0”. If the flag is “1”, the field is 8 bits. An additional copy information field is 8 bits if the AC flag is “1”.
When recording is carried out by the satellite receiver or high-definition TV decoder and compressed video data is encoded in encoder 101, it is converted into a packet form in packet processing portion 122 102 as shown in FIG. 1. If the compressed audio data is encoded in audio encoder 103, it is converted into a packet form in packet processing portion 104.
When the outputs of packet processing portions 102 and 104 are multiplexed in transmission multiplexer 105, a fixed transmission stream shown in
This public-key encryption system has all users U hold unique encryption algorithm EPK U and description algorithm DPK U. Here, encryption algorithm EPK U for the public-key is opened as a public-key to key supply portion 107. Decryption algorithm DPK U for secret key is kept in secret. The characteristics of EPK U and DPK U are as follows.
First, with respect to all users U and message m transmitted, DPK U(EPK U(m))=m.
Second, encryption algorithm EPK U and decryption algorithm DPK U do not require complicated calculation.
Third, it is impossible to find DPK″ U satisfying DPK″ U (EPK U(m))=m from encryption algorithm EPK U.
In the encryption system having the above characteristics, as shown in
Key decrypter 108 receiving the key information from key supply portion 107 outputs an algorithm DPK B, corresponding to encryption algorithm EPK B, decryptor 109 decrypts (DPK B(c))=m) the output of encrypter 106 with decryption algorithm DPK B, and then transmits to user B. In other words, only user B can decrypt decryption algorithm DPK B corresponding to encryption algorithm EPK B.
A concept developed from the public-key encryption is presented in U.S. Pat. No. 4,405,829. This public-key encryption system is called RSA system. A method in which the RSA public-key encryption is efficiently calculated via batch processing is presented in U.S. Pat. No. 4,964,164.
However, this public-key encryption is inappropriate for high-velocity encryption. A CA system is intended to present prevent illegal view viewing. However, there is no method of protecting a program distributed through a digital storage medium such as a digital VCR.
Therefore, it is an object of the present invention to an illegal copy prevention method and apparatus for a digital video system in which, in copy tape, encrypted key information is transmitted and recorded so that a copied tape is reproducible only in a VCR having a corresponding encrypted key information, thereby prevented copy.
To accomplish the object of the present invention, there is provided a copy prevention method for a digital video system comprising 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 field of the decrypted and transmitted bit stream and detecting copy prevention information; and (d) encrypting the bit stream according to information detected from step (c) and recording it on tape.
For the object of the present invention, there is provided a copy prevention apparatus for a digital video system comprising: a reproduction block for adding key information to a reproduced bit stream, and decrypting and transmitting it; and a recording block for searching key information of the bit stream transmitted from the reproduction block is extract copy prevention information, and encrypting and recording the bit stream according to the extracted copy prevention information.
The reproduction block comprises: reproduction means for reproducing data recorded on tape; key insertion means for adding key information to the bit stream of the reproduction means; and decryption means for decrypting the output of the key insertion means and transmitting it to a recording-side VCR.
The recording block comprises: key detecting/correcting means for detecting key information from the transmitted bit stream of a reproducing-side VCR: copy prevention information detecting means for searching the key information detected from the key detecting/correcting means to detect copy prevention information; encrypting means for encrypting the bit stream according the copy prevention information of the copy prevention information detecting means; and recording means for recording the bit stream encrypted in the encrypting means.
The copy prevention information detecting means comprises: a PES header detecting portion for detecting a PES header from parallel data output from the key detecting/correcting means; and a copy prevention information extractor enabled by a PES header detection signal of the PES header detecting portion to detect an additional copy information field.
To accomplish the objects of the present invention, there is provided a copy protection method comprising receiving encrypted digital data to be recorded, key information which is required to decrypt the encrypted digital data, and first copy control information which indicates a copy permission status of the encrypted digital data; and recording the encrypted digital data, the key information, and second copy control information on a digital recording medium, based on at least a status of the first copy control information.
According to another object there is provided a copy protection method comprising (a) providing digital content, key information for controlling at least decryption of the digital content, and copy control information for controlling copying of the digital content; and (b) recording the key information, the copy control information and the digital content on a digital recording medium.
According to another object there is provided a copy protection method comprising receiving encrypted digital content, first key information for decrypting the encrypted digital content, and copy control information which indicates whether or not a copy of the encrypted digital content is permitted; and controlling a recording or a reproducing of the encrypted digital content on or from a recording medium based on the first key information and/or the copy control information.
According to another object there is provided a copy protection apparatus comprising a receiving unit configured to receive encrypted digital data to be recorded, key information which is required to decrypt the encrypted digital data, and first copy control information which indicates a copy permission status of the encrypted digital data; and a recording unit configured to record the encrypted digital data, the key information, and second copy control information on a digital recording medium, based on at least a status of the first copy control information.
According to another object there is provided a copy protection apparatus comprising a providing unit configured to provide digital content, key information for controlling at least decryption of the digital content, and copy control information for controlling copying of the digital content; and a recording unit configured to record the key information, the copy control information and the digital content on a digital recording medium.
According to another object there is provided a copy protection apparatus comprising a receiving unit configured to receive encrypted digital content, first key information for decrypting the encrypted digital content, and copy control information which indicates whether or not a copy of the encrypted digital content is permitted; and a controlling unit configured to control a recording or a reproducing of the encrypted digital content on or from a recording medium based on the first key information and/or the copy control information.
Hereinafter, a preferred embodiment of the present invention will be described below with reference to the attached drawings.
As shown in
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 FIG. 4.
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 FIG. 11C.
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 EPK U corresponding to the public-key and decryption algorithm DPK U corresponding to the secret key. Encryption algorithm EPK U takes a power key of VCR u, and decryption algorithm DPK U 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 EPK A. 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 DPK A[EPK A (Y)] in which data is decrypted properly. In other VCRs, key Y cannot be found, which disables the decryption of the bit stream.
AsAn 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 FIG. 7. When bit stream data_in is input as shown in
Here, packet start code detecting portion 13 searches the bit stream shown in FIG. 8A and the output of first and second flipflops 11 and 12 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 FIG. 9. When the parallel data output from PES header detector 10 and 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 FIG. 10B. The field is output as shown in FIG. 10C.
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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|U.S. Classification||380/201, 705/58, 705/57, 380/228|
|International Classification||H04N5/913, G11B20/12, H04N5/92, A47L9/26, H04L9/32, G09C1/00, G11B20/10, H04N5/91, H04K1/00, H04L9/00, H04N7/167|
|Cooperative Classification||H04N5/913, H04N9/8205, H04N9/8042, H04N2005/91364, H04N2005/91328, H04N9/8063|