CN100496118C - Method for encrypting/deciphering residual quotiety amplitude value in H.264 standard video information - Google Patents
Method for encrypting/deciphering residual quotiety amplitude value in H.264 standard video information Download PDFInfo
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Abstract
The invention relates to a kind of encryption and deciphering method of remained difference coefficient breadth in H. 264 standard video information, it characterized in that: based on self adapting updating rule of remained difference coefficient breadth coding middle variable suffiXLength, adopting difference value absolute value which calculates current remained difference coefficient breadth and suffixLength self adapting updating threshold value, then based on the difference value absolute value, deciding bit number of last bit of the remained difference coefficient breadth which is to be encrypted, video code flow encrypted fulfill the H. 264 standard format. The characteristics of the invention are following: independent on video coder and decoder, video code flow encrypted fulfill the H. 264 standard; complexity of calculation is low, can fulfill the real time requirement of video information process and transmission; not affect the compression ratio; not affect video communication and network fault tolerant of video transmission; secrecy class can be realized; independent on concrete cryptogram arithmetic, it can use different international normal cryptogram arithmetic, the secrecy can achieve level that current technique can not decrypt.
Description
Technical field
The invention belongs to video secure communication field, is the encipher-decipher method of residual error coefficient amplitude in a kind of H.264 normal video information specifically.
Background technology
Increasingly extensive along with various Video Applications, the safety problem of video information also becomes increasingly conspicuous.It is the main and prior means that solve video information safety that information source is encrypted the encryption of promptly carrying out video content itself.Even the encryption to video content itself can guarantee that the disabled user has obtained video information, do not watch original correct video image owing to there is key correctly to decipher.
Because video information has mass data, in concrete the application, for example in video telephone or video conference application, per second must transmit tens width of cloth images, all videos information is encrypted at the universality cryptographic algorithm of general information (binary system or text) if adopt, its amount of calculation is huge, with producing bigger additional delay, is difficult to satisfy the real-time requirement of video communication.
Except that confidentiality and real-time, keeping the compatibility of form is the important need of video-encryption algorithm.The implication of format compatible be the video cipher-text information syntactic-semantic still with operating such, the performance of its core is that the video cipher-text information still can be decoded smoothly by standard decoder.Keep the importance of format compatible mainly be following some:
1) keep video format and operating such can guarantee that channel informations such as Network Synchronization during original video is expressly and fault-tolerant field are not changed, thus the network-adaptive and the fault-tolerance of assurance ciphertext code stream.
2) keep format information such as video syntactic-semantic and operating such also just to keep in the video code flow fixed field such as various initial code word format information constant, these fields are owing to open being widely known by the people in agreement or standard, if these fields are encrypted, so also will cause known plain text attack, be unfavorable for the safety of video information.
3) keep video format and operating such to help control to the efficient, flexible of the video information content of commerce application.In commercial applications such as video request program, pay TVs, buy in order to attract the user, need to allow the unauthorized user displaying video ciphertext code stream of decoding smoothly to watch certain video content often.
4) keep the constant normal use that also helps the standard code video information towards storage of video format, because keep format compatible can keep all information or attribute except that video content constant, make video information still can be retrieved, and help keeping the interactive function such as F.F., rewind down of video information.
The digital video encryption technology has been accompanied by the development of video compression coding standard and constantly development always since middle nineteen nineties produces.Video-encryption technology based on dct transform and predictive coding mixed system and Huffman variable-length code decode (H.261/H.263 and MPEG-1/MPEG-2/MPEG-4) has produced a lot of achievements in research.The method of wherein main flow is exactly to select to comprise in the video information key message of video image content: residual error coefficient, motion vector and quantization step etc. carry out selective encryption.Along with the develop rapidly of hardware performance, H.264/AVC because its good compression efficient, picture quality and network fault tolerance will replace former series standard.Yet, because H.264/AVC adopted infra-frame prediction, waited a lot of complete encoding and decoding techniques different from the past based on contextual adaptive variable length coding (CAVLC), former video-encryption achievement in research major part all is not suitable for the H.264/AVC encryption of standard code video.
For emerging intra prediction mode word and I_PCM mode macro in the code stream H.264, and the motion vector of having used the Exp-Golomb entropy coding instead still can use for reference some basic thoughts of the video-encryption achievement of existing maintenance format compatible, such as it is carried out selective encryption.But, H.264 the residual error coefficient in adopts based on contextual coding strategy (CAVLC), tight association before and after the residual error coefficient amplitude code word context behind its coding, directly the smooth decoding of other residual error coefficient amplitudes of context will be influenced, thereby its format compatible certainly will be destroyed its encryption or selection standing part bit encryption.And H.264/AVC the video-encryption achievement in research of current maintenance format compatible is not suitable for normally based on the Huffman entropy coding, and therefore how encrypting residual error coefficient amplitude in the code stream H.264, to keep format compatible simultaneously be a difficult point.
For standard H.264, when brightness and chrominance block residual error data were used the CAVLC encoding and decoding, residual error coefficient was made up of hangover coefficient code word, nonzero coefficient amplitude prefix level_prefix and suffix level_suffix code word.The symbol of last several hangovers ± 1 coefficient of hangover coefficient indication residual block, the number of hangover coefficient therefore can be according to its number directly to its encryption to the hangover coefficient by the initial code word coeff_token indication of each residual block.Promptly when decoding analysis coeff_token hangover coefficient number is k, then can directly encrypt k bit following closely.The amplitude level encoding and decoding more complicated of nonzero coefficient.The level_prefix code word certainly will will be destroyed the code stream compatibility according to the variable length code table encoding and decoding of stipulating in the agreement to the direct encryption of its code word.The variable that suffixLength and levelCode need use when being coding.Suffix level_suffix is that length is the signless integer of levelSuffixSize bit, generally, the value of levelSuffixSize equals the value of variable suffixLength, but two kinds of situations exception is arranged: 1, equal 14 and suffixLength when equaling 0 when prefix, levelSuffixSize equals 4; 2, when prefix equals 15, levelSuffixSize equals 12.
Variable suffixLength is based on that context-adaptive upgrades, and the value (level) of the value of the renewal of suffixLength and current suffixLength and the nonzero coefficient of having decoded is relevant.SuffixLength is after initialization, and the adaptive updates rule is: if current decoded zero coefficient values greater than (3＜＜(suffixLength-1)), and current suffixLength is less than 6 o'clock, suffixLength adds 1.("＜＜", "〉〉 " divide be expressed as binary shift left, shift right operation symbol)
Variable levelCode equal (level_prefix＜＜suffixLength)+level_suffix.Then the level value is drawn by following rule: if levelCode is an even number, the value of level is (levelCode+2)〉〉 1; Otherwise, the value of level be (level-1)〉〉 1.Therefore to the change of levelCode small change all can causing level value symbol.So level_suffix is done small change and just may cause the variation that the level value is bigger, thereby thereby can consider to encrypt level_suffix reaches the purpose of encrypting residual error coefficient.
But, can not directly encrypt whole level_suffix, because the change of level_suffix can cause the change of the adaptive updates of suffixLength, cause the mistake of when the next residual error coefficient amplitude code word of decoding, this code word level_suffix length being judged, just destroy the code stream semantic format, certainly will cause the decoding failure.So, need consider to influence the adaptive updates process of suffixLength to the encryption of level_suffix.
Summary of the invention
Purpose of the present invention is exactly at residual error coefficient amplitude in the whole H.264 code stream of direct encryption or encrypts the problem that its standing part bit will certainly destroy format compatible, by anatomizing in the code stream H.264 encoding-decoding process and context relation characteristics based on the residual error coefficient of CAVLC entropy coding, and a kind of encipher-decipher method of residual error coefficient amplitude in a kind of corresponding H.264 normal video information proposed, and feasible encryption keeps format compatible simultaneously, to overcome above-mentioned deficiency.
The present invention does not destroy semantic format in order to make encryption residual error coefficient amplitude, dynamic analysis is the code stream of each coded slice H.264, the adaptive updates rule of suffixLength during according to the residual error coefficient amplitude coding adopts the adaptive refinement method, and its concrete adaptation rule is as follows:
(1) equals 14 and suffixLength when equaling 0 when prefix, the level_suffix of 4bit is directly encrypted.
(2) when prefix equals 15, the level_suffix of 12bit is directly encrypted.
(3) when suffixLength more than or equal to 6 the time, suffixLength no longer upgrades, and level_suffix is directly encrypted.
(4) when above-mentioned three kinds of specific conditions do not satisfy, (suppose suffixLength adaptive updates threshold value 3＜＜(suffixLength
Represent with hread, the absolute value Abs (level-thread) of current level value and thread difference represents with abs_diff), when abs_diff greater than (1＜＜k) time, back k the bit. that can encrypt suffixLength can guarantee to encrypt the relation that can not impact level and threshold value like this, thereby influence the judgement of suffixLength adaptive updates, thereby guarantee the semantic format compatibility.
To achieve these goals, method of the present invention is: need to calculate the absolute difference of current level value and thread earlier, then according to the size of this absolute difference, decide and encrypt several bits.Comprehensive above-mentioned four kinds of situations, the residual error coefficient amplitude encryption method that the present invention proposes are that needs carry out dynamic analysis and the adaptive process that determines how to encrypt.
In addition, the present invention proposes to encrypt the residual error coefficient amplitude and adds dense motion vector, intra prediction mode word, quantization parameter, residual error coefficient hangover coefficient part and I_PCM macro block pixels information to combine the confidentiality that complete scheme of composition realizes video information.
The pixel value of the hangover part of the 3bit predictive mode word of 4 * 4 luminance block, residual block coefficient and I_PCM macro block accessed to your password learn algorithm and directly encrypt.
16x16 luminance block and chrominance block intra prediction mode word are encrypted its last bit.
Quantization step, motion vector difference value are encrypted the suffix portion of its Exp-Golomb code word.And, then dynamically determine the bit length of its level_suffix that can encrypt part according to adaptive approach proposed above to the residual error coefficient amplitude.
This selection partial bit encryption method is in order to keep video code flow still to meet H.264 reference format after encryption.Above-mentioned concrete encryption method is by determining behind the syntactic-semantic of analysing in depth H.264 standard code and the decode procedure.Therefore encrypt according to the method described above according to standard H.264 and can guarantee that form is constant.
During specific implementation, analyze H.264 video code flow, according to above-mentioned Rule Extraction data bit to be encrypted, can select for use various high-intensity cryptographic algorithms (as block cipher AES/IDEA or stream cipher algorithm A5/RC4 etc.) to encrypt flexibly, the ciphertext of the critical data after will encrypting then is reduced to extracting position and those not encrypted plaintexts mix as the video code flow output after encrypting, and deciphering then is opposite process.
Because the adaptive updates rule of suffixLength when the present invention is based on the residual error coefficient amplitude coding, adopted corresponding adaptive refinement method, make the present invention have the following advantages: to obtain the still video code flow of conformance with standard form after the video information that 1, meets standard is H.264 encrypted, guarantee the video normal use; 2, the data volume of encryption and decryption is little, and computation complexity is low, can guarantee the real-time Transmission of video information; 3, residual error coefficient has comprised the multitude of video image content information, can significantly improve the video information confidentiality to its encryption (combining with other information of encryption); 4, can be for the various selection to different cryptographic algorithms be provided to the user, the convenient renewal of cryptographic algorithm upgraded.
Description of drawings
Fig. 1 is an encryption residual error coefficient amplitude method schematic diagram of the present invention.
Fig. 2 is a theory diagram of the present invention.
Fig. 3 is the application overview flow chart of the present invention in normal condition.
Fig. 4 is the application overview flow chart of the present invention in abnormal condition.
Fig. 5 encrypts the implementation method flow chart for the present invention.
Fig. 6 deciphers the implementation method flow chart for the present invention.
Embodiment
Below in conjunction with drawings and Examples the present invention is done further to be description, but following examples should not be construed as limitation of the present invention.
The application flow of this method such as Fig. 3.
Video-encryption module among Fig. 1 promptly is the realization part of this method.Original video code stream after overcompression obtains still standard compliant video code flow through the video-encryption module, reverts to original video code flow through the code stream after encrypting through deciphering module, just can obtain correct video image through decoder then.But, if through the code stream after encrypting not by deciphering module or do not obtain correct decruption key, then obtain ruined video image (Fig. 4) through decoder.
Encryption flow of the present invention such as Fig. 5.The video-encryption module of this method mainly is made up of three parts: code stream analysis module cryptographic algorithm encrypting module and code stream mixing module.The code stream analysis module functions is to read the original video code stream of analyzing after the compression, wherein defined critical data is extracted combine, and writes down position and the length information (with bit is unit) of each critical data in code stream simultaneously.The major function of cryptographic algorithm encrypting module is to use existing generally acknowledged high-intensity cryptographic algorithm that the critical data of extracting is encrypted.To be ciphertext that encryption is obtained according to the record of the position of each critical data and length information turn back to the major function of code stream mixing module again goes to substitute the critical data of extracting in the code stream before encrypting in the source code flow, promptly mixes the ciphertext code stream after obtaining encrypting with other non-critical data.
The present invention deciphers flow process such as Fig. 6.The decryption of video inside modules structure of this method mainly is made up of three parts: code stream analysis module, cryptographic algorithm deciphering module and code stream mixing module.The code stream analysis module functions is to read the video code flow of analyzing through after encrypting, the ciphertext of wherein the critical data after encrypting extracted combine, write down position and the length information (with bit is unit) of ciphertext in code stream of each critical data simultaneously.The major function of cryptographic algorithm deciphering module is to use cryptographic algorithm consistent when encrypting that the ciphertext of the critical data extracted is decrypted.The major function of code stream mixing module is that the critical data of will deciphering back restoring expressly turns back to again according to the record of the position of each critical data ciphertext and length information and goes in the code stream to substitute the encrypt data that extracts before the deciphering, promptly mixes the plaintext code stream after obtaining deciphering with other non-encrypt datas.
Cryptographic algorithm of the present invention can be selected block cipher (3DES, AES, IDEA etc.) or stream cipher algorithm (A5, RC4, SEAL etc.) for use, but is not limited to above-mentioned algorithm, also can select certain particular algorithm of user's appointment according to user's needs.Cryptographic algorithm can be designed to independently software or hardware interface, can in the encryption and decryption module, select flexibly and change.
The present invention obtains the encryption method of different privacy levels to adapt to the application demand of different stage by the encryption to the various combination of key message in H.264.These key messages comprise: residual error coefficient amplitude, motion vector, intra prediction mode word, quantization parameter, residual error coefficient hangover coefficient part and I_PCM macro block pixels information.
The video information normal use need be considered following five aspects emphatically.Practical requirement does not influence application to the video encrypting/deciphering method that the present invention proposes owing to be devoted to as far as possible, so the very little even basic not influence of influence aspect these five.
Influence to video interactive and direct control: so the encryption method that the present invention proposes is not owing to change the flag information of the relevant object in the video information and the data such as flag information of relevant fast forwarding and fast rewinding do not influence H.264 interactivity and direct control (as video code conversion) basically;
Influence to coding and decoding video and video quality: the encipher-decipher method that the present invention proposes, its encryption and decryption process is independent of encoding-decoding process, and because encryption and decryption is only operated the most basic video information, can not limit the various characteristics of encoding and decoding, therefore can not cause the loss of video quality yet;
To the code stream size is the influence of bandwidth requirement: the encryption method that the present invention proposes does not influence the video compression ratio owing to do not use the cryptographic algorithm that increases the plaintext size, does not therefore increase the code stream size substantially through encrypting;
Influence to the video transmission time-delay: the encipher-decipher method that the present invention proposes is owing to only encrypt low volume data, and the encryption and decryption computation complexity is low, so this encryption method is very little to the additional delay of video transmission, does not influence real-time substantially;
Influence to network fault tolerance: the encipher-decipher method that the present invention proposes is owing to be unit with coded slice H.264, when packet loss appears in network, lose one or several coded slice and can not influence the correct deciphering of next code sheet, so this encryption method is very little to the network fault tolerance influence.
The content that is not described in detail in this specification belongs to this area professional and technical personnel's known prior art.
Claims (6)
1, the encipher-decipher method of residual error coefficient amplitude in a kind of H.264 normal video information, it is characterized in that: the adaptive updates rule of intermediate variable suffixLength during according to the residual error coefficient amplitude coding, adopt the absolute difference of calculating current residual error coefficient amplitude and suffixLength adaptive updates threshold value earlier, then according to the size of this absolute difference, decide the bit number of last several bits of this residual error coefficient amplitude to be encrypted, the variation of encrypting back residual error coefficient amplitude does not influence contextual incidence relation, makes that encrypting the rear video code stream still meets H.264 reference format.
2, the encipher-decipher method of residual error coefficient amplitude in the H.264 normal video information as claimed in claim 1, it is characterized in that: during encryption, to encrypt the residual error coefficient amplitude, and combine complete encipherment scheme of composition with other information that contain video content of encryption and guarantee the H.264 confidentiality of normal video information.
3, the encipher-decipher method of residual error coefficient amplitude in the H.264 normal video information as claimed in claim 2 is characterized in that: the information that contains video content comprises motion vector, intra prediction mode word, quantization step, residual error coefficient hangover coefficient part and I_PCM macro block pixels information.
4, the encipher-decipher method of residual error coefficient amplitude in the H.264 normal video information as claimed in claim 2 is characterized in that: the pixel value of the hangover part of the 3bit predictive mode word of 4 * 4 luminance block, residual block coefficient and I_PCM macro block is accessed to your password learn algorithm and directly encrypt.
5, the encipher-decipher method of residual error coefficient amplitude in the H.264 normal video information as claimed in claim 2 is characterized in that: 16x16 luminance block and chrominance block intra prediction mode word are encrypted its last bit.
6, the encipher-decipher method of residual error coefficient amplitude in the H.264 normal video information as claimed in claim 2 is characterized in that: the suffix portion of quantization step, motion vector difference value being encrypted its Exp-Golomb code word.
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| US10057641B2 (en) * | 2009-03-25 | 2018-08-21 | Sony Corporation | Method to upgrade content encryption |
| CN102025996B (en) * | 2010-12-20 | 2012-09-26 | 浙江大学 | Multiple-prediction mode multiplexed H.264 interframe processing unit |
| CN103747261B (en) * | 2013-12-31 | 2017-06-27 | 北京工业大学 | H.264 compression domain hierarchical perception encryption method based on motion reference structure |
| CN108206950B (en) * | 2016-12-19 | 2021-11-12 | 北京君正集成电路股份有限公司 | Code stream length calculation method and device |
| CN108632614B (en) * | 2017-03-21 | 2021-11-05 | 中山大学 | Motion detection method based on format-compatible encrypted video |
| CN111436231B (en) * | 2018-11-12 | 2022-03-25 | Lg电子株式会社 | Method and apparatus for coding transform coefficients based on high frequency zeroing |
| CN116527903B (en) * | 2023-06-30 | 2023-09-12 | 鹏城实验室 | Image shallow compression method and decoding method |
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| CN1536532A (en) * | 2003-04-10 | 2004-10-13 | 中国科学院计算技术研究所 | Effective image compression and encryption amalgamation method |
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| CN1536532A (en) * | 2003-04-10 | 2004-10-13 | 中国科学院计算技术研究所 | Effective image compression and encryption amalgamation method |
| CN1604640A (en) * | 2004-10-28 | 2005-04-06 | 武汉大学 | A video information encrypting-decrypting method |
| CN1882082A (en) * | 2006-05-11 | 2006-12-20 | 北京经天科技有限公司 | Selective encryption algorithm aiming at network video |
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