CN102325137B - Watermarking technique combined media security distribution method - Google Patents

Abstract

The invention discloses a watermarking technique combined media security distribution method, belonging to the field of digital copyright management encryption. The method comprises the followings: 1, a step of application architecture construction; 2. a step of encryption process; 3, a step of decryption process, and 4, a step of tracing an illegal distribution person, wherein media data are decrypted to different duplicates according to different keys; encryption keys are used to scramble a column diagram of the media data in an encryption process; an inverse scramble on the column diagram of the media data is carried out in a decryption process by using decryption keys; the decryption keys are different from the encryption keys, and each decryption key consists of an encryption key and a fingerprint; and each client carries out an inverse scrambling operation on the column diagram of the media data by using the decryption key per se. According to the method provided by the invention, the media data can be distributed by using the method; the media data are encrypted on a server terminal and sent to the client; and each client decrypts the media data per se to a unique duplicate, wherein the fingerprint can be used to trace an illegal client leaking a media duplicate.

Description

A kind of media safety distribution method of combination digital watermark

Technical field

The present invention relates to a kind of digital copyright management field of encryption, more particularly, relate to a kind of media safety distribution method of combination digital watermark.

Background technology

For media releasing, fingerprint technique is a kind of suitable solution.Every client's fingerprint (client unique for example, for, Customer ID) is embedded in media data.Therefore, client can receive different copies, passes through fingerprint identity recognition.In fact,, in order to have prevented unauthorized client, when publication medium, not only to, for media data embeds fingerprint, also to be encrypted it.Therefore, we need consider that media data is encrypted wherein, deciphering and embed wherein fingerprint wherein.Generally speaking be, that media data embeds fingerprint and is encrypted at server end.But server is that different clients produces different copies, this is quite consuming time, and also unactual in the environment of broadcast or multicast.Effectively solution is exactly that the load of server end is transferred in client.Like this, server only need be to data encryption once; In client, first client is decrypted, and then embeds fingerprint.But, in this gap that may cause media data to operate at deciphering and embedding fingerprint, leak out.

Therefore,, for fear of information leakage, deciphering and fingerprint embedding seamless link need to be got up.Connect deciphering and realized deciphering and fingerprint embedding with the method for fingerprint embedding simultaneously.Up to the present, there are two kinds of algorithms ^[1,2]realize this connection.These algorithms, in server end encrypted media data, are deciphered as different copies in client.Although these algorithms can track illegal distribution person, also there is following defect:

(1) Chamloen ^[1]method taking stream cipher as basis, its is by stream cipher encrypted media data, and by fingerprint embedding in LSB.This method efficiency is high, but can not tackle signal processing (recompression, add make an uproar etc.).In addition, this method is not mentioned the safety problem of how to resist collusion attack yet.([1]R.Anderson?and?C.Manifavas，“Chamleon-Anew?kind?of?stream?cipher，”in?Lecture?Notes?in?Computer?Science，Fast?Software?Encryption，Springer-Verlag，1?997，pp.1?07-11?3.)

(2) the JFD method of Kundur ^[2]taking Partial encryption as basis, it in the time encrypting confusion the sign bit of DCT coefficient, a part of only deciphering sign bit in when deciphering.This method can be tackled signal processing; But encrypted media often can be identified, and coherent detection has reduced detection efficiency, nor can determine its opposing collusion attack fail safe.([2]D.Kundur?and?K.Karthik，“Video?fingerprinting?and?encryption?principles?for?digital?rights?management，”Proceedings?ofthe?IEEE，Vol.92，No.6，June?2004，pp.918-932.)

Summary of the invention

1. the technical problem that invention will solve

The invention reside in and overcome the deficiencies in the prior art, a kind of media safety distribution method of combination digital watermark is provided, the media after its encryption should be safe (media content after encryption do not make sense) in cognition; Media after encryption should be safe (media content after encryption do not make sense) in cognition; Media data after encryption can be decrypted according to different decruption keys is different copies; Every part of copy should comprise the fingerprint (unique client codes, as customer's identity card) of embedding, and it can tackle signal processing (add and make an uproar etc.); The fingerprint embedding in copy can easily be detected; The fingerprint embedding in copy can be used in follows the trail of illegal distribution person.

2. technical scheme

For achieving the above object, technical scheme provided by the invention is:

The media safety distribution method of a kind of combination digital watermark of the present invention, the steps include:

(1) build application architecture;

(2) ciphering process;

(3) decrypting process;

(4) illegal distribution person follows the trail of.

In the application architecture of described step (1), at transmitting terminal, according to cryptographic algorithm E, use encryption key K that original media data P is encrypted as to code data C; At receiving terminal, according to decipherment algorithm D, use different key K _j(j=0,1 ... N-1) (N>=1, N is client's number) is different copy P by code data C deciphering _j(j=0,1 ... N-1); Decruption key K _jconventionally formed by two parts: encryption key K and fingerprint F _j(j=0,1 ... N-1), i.e. K _j=K||F _j(" || " is concatenation operator); Different clients has different fingerprint F _j, i.e. F _j≠ F _i(i ≠ j); Encrypt and decrypt procedure definition is:

$\left\{\begin{array}{c}C=E(P,K)\\ P_j=D(C,K_j)(j=\mathrm{0,1},...,N-1)\end{array}\right..$

The ciphering process of described step (2) adopts watermark encrypting algorithm, and it comprises two steps: generate parameter and encrypted media.

In the generation parameter step of described watermark encrypting algorithm, according to encryption key K and encryption length L, parameter generative process produces two parameters: displacement length Y and direction of displacement W; Encryption key K is 128, encrypts length L and is greater than 32; The step that generates parameter is: generate random number, sequence of partitions and quantized sequences, wherein:

(A) generate random number

Generate a random sequence R=r by randomizer ₀r ₁r ₂... r _2N-1(0≤r _i< 1, i=0,1 ..., 2N-1) (r _ifor decimal), the input parameter that encryption key K is randomizer;

(B) sequence of partitions

Random sequence R is split into two sequence: R ₀=r ₀r ₂... r _2N-2and R ₁=r ₁r ₃... r _2N-1;

(C) quantized sequences

Sequence quantizes according to following method: R ₀=r ₀r ₂... r _2N-2be quantified as Y=y ₀y ₁... y _n-1(0≤y _i< L, i=0,1 ..., N-1) (y _ifor integer):

Wherein, represent to be not more than the maximum integer of x;

R ₁=r ₁r ₃... r _2N-1be quantified as W=w ₀w ₁... w _n-1. (w _i=1 or 0, i=0,1 ..., N-1):

Wherein, represent to be not more than the maximum integer of x.

In the encrypted media step of described watermark encrypting algorithm, when encrypted media, according to parameter displacement length Y and direction of displacement W, original media P is encrypted as to C, the step of encrypted media is: cut apart media, compute histograms, scramble histogram, draw histogram and combined medium, wherein:

(A) cut apart media

Media P is divided into N part: P ⁰, P ¹..., P ^n-1, each piece image P ⁱ(i=0 to N-1) operates according to step (B) to step (D) successively;

(B) compute histograms

By image block P ⁱbe divided into two sub-block A and B, A is by image block P ⁱin all even number lines composition, B is by P ⁱin all odd-numbered lines composition, calculate respectively the histogram H of sub-block A and B _awith H _b;

(C) scramble histogram

Adopt random transition method, according to direction of displacement w _iwith displacement length y _iscramble histogram H _awith H _b, the histogram after scramble is respectively H ' _aand H ' _b,

$\left\{\begin{array}{c}{H_a}^{\&prime;}=S(H_a,1-w_i,y_i)\\ {H_b}^{\&prime;}=S(H_b,w_i,L-y_i)\end{array}\right.$

Wherein, S () represents cycle shift operation, w _irepresent direction of displacement (0 represents to the right, and 1 represents left), y _irepresent displacement length;

(D) draw histogram

By H _a' and H _b' reverse sub-block A and the B of being plotted as, sub-block A ' and the B ' of generation scramble, be combined into cryptographic block C by A ' and B ' ⁱ, wherein even number line derives from sub-block A ', and odd-numbered line derives from sub-block B ', after N iterative cryptographic, produces N cryptographic block, is respectively C ⁰, C ¹..., C ^n-1;

(E) media combination

According to the media cutting procedure in step (A), by N cryptographic block C ⁰, C ¹..., C ^n-1be grouped together, produce encrypted media C.

The decrypting process of described step (3) adopts watermark decipherment algorithm, and the step of watermark decipherment algorithm is: Split Key, generate the compound and decrypt media of parameter, finger-print codes, parameter, wherein:

(A) Split Key

Decruption key K _j=K||F _j(" || " is concatenation operator) is divided into two parts: encryption key K and fingerprint F _j(j=0,1 ..., N-1);

(B) generate parameter

According to definite in advance encryption key K and encryption length L, generate and produce two parameters: displacement length Y and direction of displacement W;

(C) finger-print codes

According to the coding method that can resist collusion attack to fingerprint F _jencode, coding method is orthogonal finger-print codes or the finger-print codes based on embedding hypothesis or the finger-print codes method based on assembly coding, and finger-print codes is F _j=f _{j, 0}f _{j, 1}... .f _{j, N-1}(f _{j, i}=0 or 1, i=0,1 ..., N-1);

(D) parameter is compound

Compound displacement length Y=y ₀y ₁... y _n-1with fingerprint F _j=f _{j, 0}f _{j, 1}... f _{j, N-1}after, produce new displacement length Q _j=q _{j, 0}q _{j, 1}... q _{j, N-1}, satisfy condition:

$q_{j,i}=L-y_i+{(-1)}^{f_{j,i}}(j=\mathrm{0,1},...,N-1,i=\mathrm{0,1},...,N-1);$

(E) decrypt media

In media decrypting process, according to direction of displacement W and new displacement length Q _jbe P by media data C deciphering _j.

The step of described step (E) decrypt media is:

1) cut apart media

Media C after encryption is divided into N piece: C ⁰, C ¹..., C ^n-1, each cryptographic block C ⁱ(i=0to N-1) operates to 5.4 according to step 5.2 successively;

2) compute histograms

Calculate cryptographic block C ⁱin the histogram of each sub-block, result is respectively H ' _awith H ' _b;

3) histogram inverted disorderly

According to displacement length q _{j, i}with direction of displacement w _i, the random H ' of random inverted _awith H ' _b, the histogram after scramble is respectively H " _awith " _b,

$\left\{\begin{array}{c}{H}_a^{\&prime;\&prime;}=S(H_a^{\&prime;},w_i,y_i)\\ H_b^{\&prime;\&prime;}=S(H_b^{\&prime;},1-w_i,q_{j,i})=S(H_b,1-w_i,L-y_i+{(-1)}^{f_{j,i}})\end{array}\right.,$

Wherein, S () represents circulative shift operation;

4) draw histogram

By the histogram H of inverted unrest " _awith H " _breverse sub-block A and the B of being plotted as, produces deciphering sub-block A ' and B ' in this process, then combine A ' and B ' and draw decryption block C ^{j, i}, wherein even number line derives from scramble sub-block A ', and odd-numbered line derives from B ', encrypts after iteration N time generation cryptographic block: C ^{j, 0}, C ^{j, 1}..., C ^{j, N-1};

5) combined medium

By N cryptographic block C ^{j, 0}, C ^{j, 1}..., C ^{j, N-1}, according to step 1) in media cutting procedure combine, produce decrypt media P _j.

Illegal distribution person in described step (4) follows the trail of, and is embedded in media copy P by extraction _jin fingerprint, realize tracking to illegal distribution person, fingerprint extraction process is similar with media decrypting process, different to media encryption, and each cryptographic block is only carried out to histogrammic calculating, comparison, does not carry out scramble operation;

According to equation $\left\{\begin{array}{c}{H_a}^{\&prime;}=S(H_a,1-w_i,y_i)\\ {H_b}^{\&prime;}=S(H_b,w_i,L-y_i)\end{array}\right.$ With $\left\{\begin{array}{c}{H}_a^{\&prime;\&prime;}=S(H_a^{\&prime;},w_i,y_i)\\ H_b^{\&prime;\&prime;}=S(H_b^{\&prime;},1-w_i,q_{j,i})=S(H_b,1-w_i,L-y_i+{(-1)}^{f_{j,i}})\end{array}\right.,$

Simplify:

$\left\{\begin{array}{c}{H}_a^{\&prime;\&prime;}=S(H_a^{\&prime;},w_i,y_i)=S(S(H_a,1-w_i,y_i),w_i,y_i)=H_a\\ H_b^{\&prime;\&prime;}=S(S(H_b,w_i,L-y_i),1-w_i,L-y_i+{(-1)}^{f_{j,i}})=S(H_b,1-w_i,{(-1)}^{f_{j,i}})\end{array}\right.,$

Therefore, H " _awith H _aidentical, and H " _bwith H _bslightly difference, this represents that decrypt media copy and clean copy have JND, this difference depends on fingerprint; Due to H _awith H _bconsistent substantially, so by contrast H " _awith H " _b, can detect the difference of maximum frequency position in each histogram, thereby can extract fingerprint bit F _{j, i}, therefore, by analyzing all close, extract finger-print codes F _j=f _{j, 0}f _{j, 1}... f _{j, N-1}, can confirm illegal client.

3. beneficial effect

Adopt technical scheme provided by the invention, compared with existing known technology, there is following remarkable result:

(1) by selecting higher Cipher Strength to ensure the fail safe of media in cognition.Higher Cipher Strength can make the media data after encryption identify;

(2) media data is decrypted according to different keys is different copies;

(3) fingerprint embedding can be tackled approved operation, makes an uproar as added;

(4) fingerprint embedding is easy to be detected;

(5) according to collusion antagonism coding method, fingerprint is encoded, this can ensure the fail safe of fingerprint in the time detecting illegal distribution person.

Brief description of the drawings

Fig. 1 is application architecture schematic diagram of the present invention;

Fig. 2 is watermark encrypting algorithm schematic diagram of the present invention;

Fig. 3 is parameter generative process of the present invention;

Fig. 4 is media encryption process of the present invention;

Fig. 5 is the histogram example that the present invention calculates;

Fig. 6 is histogram scramble example;

Fig. 7 is watermark decipherment algorithm schematic diagram of the present invention;

Fig. 8 is media decrypting process of the present invention;

Fig. 9 is fingerprint extraction process of the present invention;

Figure 10 the present invention is based on the image encryption/deciphering of algorithm herein;

Robustness when Figure 11 is noise resistance of the present invention;

Figure 12 is system applies structure of the present invention.

Embodiment

The present invention is made up of five parts: application architecture, and ciphering process, decrypting process, illegal distribution person follows the trail of, system and experimental result.Be described as follows:

1. application architecture

The application scenarios of the present invention: in server end encrypted media data, again the data after encrypting are sent to client, every client is different copies with different keys by media data deciphering, comprises the fingerprint (for example user ID) of identification recipient identity in every part of copy.

Application architecture as shown in Figure 1.At transmitting terminal, according to watermark encrypting algorithm E, use encryption key K that original media data P is encrypted as to code data C.At receiving terminal, according to watermark decipherment algorithm D, use different key K _j(j=0,1 ... N-1) (N>=1, N is client's number) is different copy P by code data C deciphering _j(j=0,1 ... N-1).Decruption key K _jconventionally formed by two parts: encryption key K and fingerprint F _j(j=0,1 ... N-1).That is to say K _j=K||F _j(" || " is concatenation operator).Different clients has different fingerprint F _j, i.e. F _j≠ F _i(i ≠ j).Encrypt and decrypt procedure definition is:

$\left\{\begin{array}{c}C=E(P,K)\\ P_j=D(C,K_j)(j=\mathrm{0,1},...,N-1)\end{array}\right.---\left(1\right)$

Wherein, watermark encrypting algorithm E () and watermark decipherment algorithm D () will specifically introduce hereinafter.

2. watermark encrypting algorithm

As shown in Figure 2, it comprises two steps to watermark encrypting algorithm: generate parameter and encrypted media.

2.1 generate parameter

According to encryption key K and encryption length L, parameter generative process produces two parameters: displacement length Y and direction of displacement W.Encryption key K is 128; Encrypt length L and be greater than 32, can determine in advance.In general, L gets 256.As shown in Figure 3, it comprises three steps to the generative process of parameter: generate random number, sequence of partitions and quantized sequences.

Step 1, generates random number

By randomizer generate random sequence R=r0r1r2......r2N-1 (0≤ri < 1, i=0,1 ..., 2N-1) (ri is decimal).Encryption key K is the input parameter of randomizer.Can utilize existing random data generator, the random data generator of for example recommending in [1].

Step 2, sequence of partitions

Random sequence R is split into two sequence: R0=r0r2...r2N-2 and R1=r1r3...r2N-1.

Step 3, quantized sequences

Sequence quantizes according to following method: R0=r0r2...r2N-2 be quantified as Y=y0y1...yN-1 (0≤yi < L, i=0,1 ..., N-1) (yi is integer):

Wherein, represent to be not more than the maximum integer of x.R ₁=r ₁r ₃... r _2N-1be quantified as W=w ₀w ₁... w _n-1. (w _i=1 or 0, i=0,1 ..., N-1):

Wherein, represent to be not more than the maximum integer of x.

2.2 encrypted media

When encrypted media, according to parameter displacement length Y and direction of displacement W, original media P is encrypted as to C.As shown in Figure 4, it comprises following five steps to ciphering process: cut apart media, and compute histograms, scramble histogram, draws histogram and combined medium.Below will specifically set forth.

Step 1, cuts apart media

Media P is divided into N part: P0, P1 ..., PN-1.Taking image as example, certain image is split into N piece.The size of each piece can be different, but all can not be less than 8*8.

Each piece image Pi (i=0 to N-1) operates according to step 2 to step 4 successively.

Step 2, compute histograms

Image block Pi is divided into two sub-block A and B.A is made up of all even number lines in image block Pi, and B is made up of all odd-numbered lines in Pi.Calculate respectively histogram Ha and the Hb of sub-block A and B, histogrammic computing reference [2].Fig. 5 is the histogram example calculating.Because of for to be gone out by same image calculation, so having similar gray scale frequency, they distribute, particularly maximum frequency position is similar.The position of maximum frequency will be used for extracting the finger print information embedding.

Step 3, scramble histogram

Adopt random transition method, according to direction of displacement wi and displacement length yi scramble histogram Ha and Hb.Histogram after scramble is respectively H ' a and H ' b.

$\left\{\begin{array}{c}{H_a}^{\&prime;}=S(H_a,1-w_i,y_i)\\ {H_b}^{\&prime;}=S(H_b,w_i,L-y_i)\end{array}\right.---\left(4\right)$

Wherein, S () represents cycle shift operation, and wi represents direction of displacement (0 represents to the right, and 1 represents left), and yi represents the length that is shifted.For example, establish wi=1, as Fig. 6, Ha is moved from the left to the right through yi step, and Hb walks by the right-hand left side that moves to through L-yi.

Step 4, draws histogram

By Ha ' and reverse sub-block A and the B of being plotted as of Hb ', produce sub-block A ' and the B ' of scramble.A ' and B ' are combined into cryptographic block Ci, and wherein even number line derives from sub-block A ', and odd-numbered line derives from sub-block B '.

After N iterative cryptographic, produce N cryptographic block, be respectively C0, C1 ..., CN-1.

Step 5, media combination

According to the media cutting procedure in step 1, by N cryptographic block C0, C1 ..., CN-1 is grouped together, and produces encrypted media C.

3. watermark decipherment algorithm

As Fig. 7, watermark decipherment algorithm is made up of 5 steps: Split Key, generates parameter, finger-print codes, the compound and decrypt media of parameter.

Step 1, Split Key

Decruption key Kj=K||Fj (" || " is concatenation operator) is divided into two parts: encryption key K and fingerprint Fj (j=0,1 ..., N-1).

Step 2, generates parameter

According to definite in advance encryption key K and encryption length L, generate and produce two parameters: displacement length Y and direction of displacement W.This process identical with the process in 2.1 (seeing Fig. 3).

Step 3, finger-print codes

According to the coding method that can resist collusion attack, fingerprint Fj is encoded.Coding method can be orthogonal finger-print codes [3], based on the finger-print codes [4] that embeds hypothesis, finger-print codes method [5] based on assembly coding etc.Finger-print codes is Fj=fj, 0fj, and 1...fj, N-1 (fj, i=0 or 1, i=0,1 ..., N-1).

Step 4, parameter is compound

Compound displacement length Y=y0y1...yN-1 and fingerprint Fj=Fj, 0fj, 1...fj, after N-1, produces new displacement length Qj=qj, 0qj, 1...qj, N-1, satisfies condition:

$q_{j,i}=L-y_i+{(-1)}^{f_{j,i}}(j=\mathrm{0,1},...,N-1,i=\mathrm{0,1},...,N-1)---\left(5\right)$

Step 5, decrypt media

In media decrypting process, be Pj according to direction of displacement W and new displacement length Qj by media data C deciphering, as Fig. 8.Media encryption similar process in this and Fig. 4.Decrypting process is made up of following 5 steps.

Step 5.1, cuts apart media

According to method similar in Fig. 4, the media C after encryption is divided into N piece: C0, C1 ..., CN-1.

Each cryptographic block Ci (i=0to N-1) operates to 5.4 according to step 5.2 successively.

Step 5.2, compute histograms

According to the method in Fig. 4, calculate the histogram of each sub-block in cryptographic block Ci, result is respectively H ' a and H ' b.

Step 5.3, histogram inverted disorderly

According to displacement length q _{j, i}with direction of displacement w _i, the random H ' of random inverted _awith H ' _b.Histogram after scramble is respectively H " _awith " _b.

$\left\{\begin{array}{c}{H}_a^{\&prime;\&prime;}=S(H_a^{\&prime;},w_i,y_i)\\ H_b^{\&prime;\&prime;}=S(H_b^{\&prime;},1-w_i,q_{j,i})=S(H_b,1-w_i,L-y_i+{(-1)}^{f_{j,i}})\end{array}\right.---\left(6\right)$

S in its mid-term () represents circulative shift operation.

Step 5.4, draws histogram

By the histogram H of inverted unrest " a and H " reverse sub-block A and the B of being plotted as of b, in this process, produce deciphering sub-block A ' and B '.Then combine A ' and B ' and draw decryption block Cj, i, wherein even number line derives from scramble sub-block A ', and odd-numbered line derives from B '.

After encryption iteration N time, produce cryptographic block: Cj, 0, Cj, 1 ..., Cj, N-1.

Step 5.5, combined medium

By N cryptographic block Cj, 0, Cj, 1 ..., Cj, N-1 combines according to the media cutting procedure in step 5.1, produces decrypt media Pj.

4. follow the trail of illegal distribution person

If the media copy after deciphering has sent to unwarranted client, method in this paper can track illegal distribution person.Be embedded in the fingerprint in media copy Pj by extraction, can realize the tracking to illegal distribution person.Similar process in fingerprint extraction process and Fig. 4 and Fig. 8.Different, each cryptographic block is only carried out to histogrammic calculating, comparison, do not carry out scramble operation.

According to waiting (4) and equation (6), simplify:

$\left\{\begin{array}{c}{H}_a^{\&prime;\&prime;}=S(H_a^{\&prime;},w_i,y_i)=S(S(H_a,1-w_i,y_i),w_i,y_i)=H_a\\ H_b^{\&prime;\&prime;}=S(S(H_b,w_i,L-y_i),1-w_i,L-y_i+{(-1)}^{f_{j,i}})=S(H_b,1-w_i,{(-1)}^{f_{j,i}})\end{array}\right.---\left(7\right)$

Therefore, H " _awith H _aidentical, and H " _bwith H _bslightly difference.This represents that decrypt media copy and clean copy have JND, and this difference depends on fingerprint.Due to H _awith H _bconsistent substantially, so by contrast H " _awith H " _b, can detect the difference of maximum frequency position in each histogram, thereby can extract fingerprint bit F _{j, i}.For example,, if w _i=0, histogram and fingerprint bit are as shown in Figure 9.Wherein, f _{j, i}=x represents that fingerprint bit cannot measure.

Therefore, by analyzing all close, just can extract finger-print codes Fj=fj, 0fj, 1...fj, N-1, for confirming illegal client.

5. system and experimental result

Image encryption is tested as shown in Figure 10 and Figure 11, and system applies structure as shown in figure 12.Wherein, Figure 10 (a) adopts watermark encrypting algorithm herein to add and is encrypted, and draws Figure 10 (b).Figure 10 (b) is None-identified, and is gem-pure through copy Figure 10 (c) of deciphering and fingerprint embedding with Figure 10 (d).Figure 10 (c) comprises finger-print codes " 100000 ", and Figure 10 (d) comprises finger-print codes " 010000 ".In average copy Figure 10 (e), comprise finger-print codes " xx0000 ", represent that this copy conspired by client 1 and client 2.Wherein, " x " represents to be averaged and cannot to determine between copy 1 and copy 2 because of fingerprint bit.Robustness when Figure 11 represents finger-print codes noise resistance.Visible, method in this paper has higher robustness than the method for Chamleon.

In practical application:

(1) transmit leg will send media data to recipient.Can use watermark encryption technology encrypted media data, by watermark decryption technology decrypt media data.Encryption key can be identical with decruption key.

(2) company need to send some images (for example medical image), MP3 audio or video to registered user.In order to prevent that client from releasing the data of receiving again, company has embedded unique code in each image or audio frequency, for different clients provides different duplicates of the document.Therefore, this code in copy can be for finding out illegal distribution person.In this case, according to watermark encryption technology encrypted media data for encryption key, but according to watermark decryption technology decrypt media data for different decruption keys.

Abbreviation:

JFD---connect deciphering and fingerprint embedding; DRM---digital copyright management; ID---proof of identification; DCT---discrete cosine transform.

Claims (1)

1. in conjunction with a media safety distribution method for digital watermark, the steps include:

(1) build application architecture;

(2) ciphering process;

(3) decrypting process;

(4) illegal distribution person follows the trail of; Wherein:

In the application architecture of step (1), at transmitting terminal, according to cryptographic algorithm E, use encryption key K that original media data P is encrypted as to code data C; At receiving terminal, according to decipherment algorithm D, use different key K _j(j=0,1 ... N-1) (N>=1, N is client's number) is different copy P by code data C deciphering _j(j=0,1 ... N-1); Decruption key K _jconventionally formed by two parts: encryption key K and fingerprint F _j(j=0,1 ... N-1), i.e. K _j=K||F _j(" || " is concatenation operator); Different clients has different fingerprint F _j, i.e. F _j≠ F _i(i ≠ j); Encrypt and decrypt procedure definition is:

$\left\{\begin{array}{c}C=E(P,K)\\ P_j=D(C,K_j)(j=\mathrm{0,1},\&CenterDot;\&CenterDot;\&CenterDot;,N-1)\end{array}\right.;$

The ciphering process of step (2) adopts watermark encrypting algorithm, and it comprises two steps: generate parameter and encrypted media;

In the generation parameter step of described watermark encrypting algorithm, according to encryption key K and encryption length L, parameter generative process produces two parameters: displacement length Y and direction of displacement W; Encryption key K is 128, encrypts length L and is greater than 32; The step that generates parameter is: generate random number, sequence of partitions and quantized sequences, wherein:

(A) generate random number

Generate a random sequence R=r by randomizer ₀r ₁r ₂r _2N-1(0≤r _i<1, i=0,1 ..., 2N-1) and (r _ifor decimal), the input parameter that encryption key K is randomizer;

(B) sequence of partitions

Random sequence R is split into two sequence: R ₀=r ₀r ₂r _2N-2and R ₁=r ₁r ₃r _2N-1;

(C) quantized sequences

Sequence quantizes according to following method: R ₀=r ₀r ₂r _2N-2be quantified as Y=y ₀y ₁y _n-1(0≤y _i<L, i=0,1 ..., N-1) and (y _ifor integer):

Wherein, represent to be not more than the maximum integer of x;

R ₁=r ₁r ₃r _2N-1be quantified as W=w ₀w ₁w _n-1. (w _i=1 or 0, i=0,1 ..., N-1):

Wherein, represent to be not more than the maximum integer of x;

In the encrypted media step of described watermark encrypting algorithm, when encrypted media, according to parameter displacement length Y and direction of displacement W, original media P is encrypted as to C, the step of encrypted media is: cut apart media, compute histograms, scramble histogram, draw histogram and combined medium, wherein:

(A) cut apart media

Media P is divided into N part: P ⁰, P ¹..., P ^n-1, each piece image P ⁱ(i=0 to N-1) operates according to step (B) to step (D) successively;

(B) compute histograms

By image block P ⁱbe divided into two sub-block A and B, A is by image block P ⁱin all even number lines composition, B is by P ⁱin all odd-numbered lines composition, calculate respectively the histogram H of sub-block A and B _awith H _b;

(C) scramble histogram

Adopt random transition method, according to direction of displacement w _iwith displacement length y _iscramble histogram H _awith H _b, the histogram after scramble is respectively H ' _aand H ' _b,

$\left\{\begin{array}{c}{H}_a^{\&prime;}=S(H_a,1-w_i,y_i)\\ H_b^{\&prime;}=S(H_b,w_i,L-y_i)\end{array}\right.$

Wherein, S() expression cycle shift operation, w _irepresent direction of displacement (0 represents to the right, and 1 represents left), y _irepresent displacement length;

(D) draw histogram

By H _a' and H _b' reverse sub-block A and the B of being plotted as, sub-block A ' and the B ' of generation scramble, be combined into cryptographic block C by A ' and B ' ⁱ, wherein even number line derives from sub-block A ', and odd-numbered line derives from sub-block B ', after N iterative cryptographic, produces N cryptographic block, is respectively C ⁰, C ¹..., C ^n-1;

(E) media combination

According to the media cutting procedure in step (A), by N cryptographic block C ⁰, C ¹..., C ^n-1be grouped together, produce encrypted media C;

The decrypting process of step (3) adopts watermark decipherment algorithm, and the step of watermark decipherment algorithm is: Split Key, generate the compound and decrypt media of parameter, finger-print codes, parameter, wherein:

(A) Split Key

Decruption key K _j=K||F _j(" || " is concatenation operator) is divided into two parts: encryption key K and fingerprint F _j(j=0,1 ..., N-1);

(B) generate parameter

According to definite in advance encryption key K and encryption length L, generate and produce two parameters: displacement length Y and direction of displacement W;

(C) finger-print codes

According to the coding method that can resist collusion attack to fingerprint F _jencode, coding method is orthogonal finger-print codes or the finger-print codes based on embedding hypothesis or the finger-print codes method based on assembly coding, and finger-print codes is F _j=f _j, 0f _j, 1 ... f _j,N- ₁(f _j,i=0 or 1, i=0,1 ..., N-1);

(D) parameter is compound

Compound displacement length Y=y ₀y ₁y _n-1with fingerprint F _j=f _j, 0f _j, 1 ... f _{j, N-1}after, produce new displacement length Q _j=q _{j, 0}q _{j, 1}q _{j, N-1}, satisfy condition:

$q_{j,i}=L-y_i+{(-1)}^{f_{j,i}}(j=\mathrm{0,1},...,N-1,i=\mathrm{0,1},...,N-1);$

(E) decrypt media

In media decrypting process, according to direction of displacement W and new displacement length Q _jbe P by media data C deciphering _j; The step of step (E) decrypt media is:

1) cut apart media

Media C after encryption is divided into N piece: C ⁰, C ¹..., C ^n-1, each cryptographic block C ⁱ(i=0to N-1) operates to 5.4 according to step 5.2 successively;

2) compute histograms

Calculate cryptographic block C ⁱin the histogram of each sub-block, result is respectively H ' _awith H ' _b;

3) histogram inverted disorderly

According to displacement length q _j,iwith direction of displacement w _i, the random H ' of random inverted _awith H ' _b, the histogram after scramble is respectively H " _awith " _b,

$\left\{\begin{array}{c}{H}_a^{\&prime;\&prime;}=S(H_a^{\&prime;},w_i,y_i)\\ H_b^{\&prime;\&prime;}=S(H_b^{\&prime;},1-w_i,q_{j,i})=S(H_b,1-w_i,L-y_i+{(1-)}^{f_{j,i}})\end{array}\right.,$

Wherein, S() expression circulative shift operation;

4) draw histogram

By the histogram H of inverted unrest " _awith H " _breverse sub-block A and the B of being plotted as, produces deciphering sub-block A ' and B ' in this process, then combine A ' and B ' and draw decryption block C ^j,i, wherein even number line derives from scramble sub-block A ', and odd-numbered line derives from B ', encrypts after iteration N time generation cryptographic block: C ^{j, 0}, C ^{j, 1}..., C ^{j, N-1};

5) combined medium

By N cryptographic block C ^{j, 0}, C ^{j, 1}..., C ^{j, N-1}, combine according to the media cutting procedure in step 1), produce decrypt media P _j;

Illegal distribution person in step (4) follows the trail of, and is embedded in media copy P by extraction _jin fingerprint, realize tracking to illegal distribution person, fingerprint extraction process is similar with media decrypting process, different to media encryption, and each cryptographic block is only carried out to histogrammic calculating, comparison, does not carry out scramble operation;

According to equation $\left\{\begin{array}{c}{H}_a^{\&prime;}=S(H_a,1-w_i,y_i)\\ H_b^{\&prime;}=S(H_b,w_i,L-y_i)\end{array}\right.$ With $\left\{\begin{array}{c}{H}_a^{\&prime;\&prime;}=S(H_a^{\&prime;},w_i,y_i)\\ H_b^{\&prime;\&prime;}=S(H_b^{\&prime;},1-w_i,q_{j,i})=S(H_b,1-w_i,L-y_i+{(1-)}^{f_{j,i}})\end{array}\right.,$ Simplify:

$\left\{\begin{array}{c}{H}_a^{\&prime;\&prime;}=S(H_a^{\&prime;},w_i,y_i)=S(S(H_a,1-w_i,y_i),w_i,y_i)=H_a\\ H_b^{\&prime;\&prime;}=S(S(H_b,w_i,L-y_i),1-w_i,L-y_i+{(-1)}^{f_{j,i}})=S(H_b,1-w_i,{(-1)}^{f_{j,i}})\end{array}\right.,$

Therefore, H " _awith H _aidentical, and H " _bwith H _bslightly difference, this represents that decrypt media copy and clean copy have JND, this difference depends on fingerprint; Due to H _awith H _bconsistent substantially, so by contrast H " _awith H " _b, can detect the difference of maximum frequency position in each histogram, thereby can extract fingerprint bit F _j,i, therefore, by analyzing all close, extract finger-print codes F _j=f _{j, 0}f _{j, 1}f _{j, N-1}, can confirm illegal client.