CN102176759A - Method for encrypting video streaming information based on hyper-chaotic sequence - Google Patents

Abstract

The invention provides a method for encrypting MPEG (moving picture experts group) video streaming information based on a hyper-chaotic sequence, which is characterized in that a streaming encryption technology is combined with a block encryption technology so as to encrypt I frames and P frames of MPEG video streaming; in an algorithm, an initial value of a four-dimensional hyper-chaotic system is taken as an external secret key, the hyper-chaotic sequence generated by the four-dimensional hyper-chaotic system is utilized, and AC (alternating current) coefficients of video images are utilized to generate an inner secret key; and an XOR operation is carried out on DC (direct current) and AC coefficients of the I frames respectively, position scrambling is carried out on luminance information of the I frames by taking a 8*8 block as a unit, the XOR operation is carried out on motion vectors of F macro blocks in the P frames, and original video information is disturbed sufficiently. In the method, the space of the secret keys is huge, and the capacity to resist brute force attacks is strong; because an encryption process is embedded into an MPEG coding process, the method is good in instantaneity; and due to the introduction of the inner secrete key, the capacity of the encryption algorithm to resist plain text attacks is strengthened.

Description

Video stream information encryption method based on the hyperchaos sequence

[technical field]

The invention belongs to field of information security technology, relate to a kind of Video stream information encryption method based on the hyperchaos sequence.

[background technology]

Fast development along with Internet technology, Video Applications based on the Streaming Media transmission is developed rapidly, bring great convenience for people's work and life, simultaneously, also emerge many serious information security issues, the popularity of video data storage and transmission and conveniency wreck it easily and attack thereupon.Video flowings such as Digital Television, video-mail, video telephone are easy to suffer artificial attack in network environment, for example leakage of information, information are stolen, the resource unauthorized is invaded and used etc., thereby the video flowing safety problem receives increasing concern in the network environment, becomes one of current problem that needs to be resolved hurrily.

In recent years, the cryptographic algorithm of a lot of images and video occurred, yet there is defective in a lot of algorithm on fail safe or enciphering rate.In the selective encryption algorithm of video flowing, stream cipher encrypting obtains very extensive studies.A good encryption method of video stream should possess following characteristics: the first, possess enough fail safes, and can effectively resist various attack; The second, real-time, the enciphering rate of assurance video stream data.Shi and Bhargava change the direct current and the sign bit of ac coefficient or the sign bit of motion vector by key of XOR and come mpeg video stream is encrypted.Figure place is few, processing speed is fast, cannot stand known plain text attack though this stream cipher encrypting method is encrypted.The assailant carries out XOR with both corresponding positions and just can easily obtain key if know original text and ciphertext.So, be not enough only with the stream cipher encrypting video data, need to increase methods such as replacement or scramble.In addition, there is mutual restriction in a lot of cryptographic algorithm on fail safe and enciphering rate, can not realize real-time.Hyperchaotic system has initial value sensitiveness and randomlikeness, have two or more Lyapunov indexes, have the dynamics more more complicated than chaos system, can have broad application prospects at information security field for cryptographic algorithm provides huge key space and good security performance.

[summary of the invention]

The present invention seeks to solve existing cryptographic algorithm and on fail safe and enciphering rate, have mutual restriction, can not realize the problem of real-time, a kind of mpeg video stream encryption method based on the hyperchaos sequence is provided, and this method has very high security performance when guaranteeing the cryptographic algorithm real-time.

The performing step of the Video stream information encryption method based on the hyperchaos sequence provided by the invention is as follows:

1st, utilize I, P, the B frame structure features of MPEG, at first the I frame is encrypted; The I frame information is carried out dct transform, and as formula (1), it is that wherein, A (0,0) is the DC coefficient in 8 * 8 the matrix A that the DCT coefficient is read in dimension, and all the other coefficients are the AC coefficient;

$F(u,v)=\frac{2}{N}C\left(u\right)C\left(v\right)\underset{x=0}{\overset{N-1}{\mathrm{\Σ}}}\underset{y=0}{\overset{N-1}{\mathrm{\Σ}}}f(x,y)\cos \frac{(2x+1)\mathrm{u\π}}{2N}\cos \frac{(2y+1)\mathrm{v\π}}{2N}---\left(1\right)$

In the formula, when u=v=0,

Work as u, v is not 0 o'clock entirely, and C (u)=C (v)=1.

2nd, select hyperchaotic system, and set its initial value x ₁(0), x ₂(0), x ₃(0), x ₄(0), adopts fourth-order Runge-Kutta method that hyperchaotic system is carried out iterative, in each iterative process, all can obtain 4 data and be x ₁(i), x ₂(i), x ₃(i), x ₄And then obtain 4 hyperchaos sequence x (i), ₁, x ₂, x ₃, x ₄, use formula (2) that 4 sequences are carried out numerical value then and handle,

x′ _j(i)＝mod((round(|x _j(i)|-floor|x _j(i)|)×10 ¹⁴)，256) (2)

In the formula, i=1,2,3 ... represent iteration the i time, j=1,2,3,4, mod () is a MOD function, and round () is a bracket function, and floor () is downward bracket function;

3rd, calculate the m value by formula (3), m ∈ [0,2] decides which group of selection to be used for encrypting by the m value;

m＝mod(x′ ₁(i)，3) (3)

m	Combinations of states
		0	{x′ 1(i)，x′ 2(i)，x′ 3(i)}
1	{x′ 1(i)，x′ 2(i)，x′ 4(i)}
		2	{x′ 2(i)，x′ 3(i)，x′ 4(i)}

If m=2, then select x ' ₂(i), x ' ₃(i), x ' ₄(i) } be used for encrypting, utilize x ' ₂Sequence is carried out the XOR cryptographic operation to DC coefficient sequence in the I frame, establishes that the DC coefficient sequence is L in the I frame _Dc, the DC coefficient sequence is L ' behind the xor operation _DcUtilize x ' ₃It is the position scramble of unit that the Y plane space is carried out with 8 * 8 block of pixels,

$L_{\mathrm{dc}}^{\′}=L_{\mathrm{dc}}\⊕x_2^{\′}---\left(3\right)$

In the formula,

The expression xor operation;

4th, the AC coefficient sequence of establishing non-zero in the I frame is L _Ac, its element number is n, the k that calculates according to formula (4) is as internal key,

$k=\frac{1}{256}(\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{L}_{\mathrm{ac}}\left(i\right),256)---\left(4\right)$

Utilize formula (5) to change the initial value of hyperchaotic system, and then, after formula (2) numerical value is handled, can obtain sequence of values based on the new hyperchaos sequence of hyperchaotic system generation

${\tilde{x}}_1\left(0\right)=x_1\left(0\right)+0.1\×k$

(5)

${\tilde{x}}_2\left(0\right)=x_2\left(0\right)+0.1\×k$

Intercepting

Preceding n data of sequence and L _AcCarry out xor operation, the sequence behind the xor operation is designated as L ' _Ac, as formula (6),

$L_{\mathrm{ac}}^{\′}=L_{\mathrm{ac}}\⊕{\tilde{x}}_1---\left(6\right)$

In the formula,

The expression xor operation; With L ' _AcCoefficient sequence is carried out the haul distance compressed encoding, with L ' then according to the ordering of Zig-Zag shape _DcCoefficient sequence is carried out differential pulse coding, carries out the Huffman coding at last, finishes the encryption of I two field picture;

5th, for guaranteeing the fail safe of algorithm, select the motion vector of F macro block in the P frame to encrypt, be provided with two macro block M ₁And M ₂, coded image macro block M ₁Be reference picture macro block M ₂Best matching blocks, their difference is exactly the poor of respective pixel values in these two macro blocks, and the difference of gained is carried out color space transformation, and does 4: 1: 1 sampling and obtain Y, C _r, C _bComponent value carries out dct transform, quantification and variable-length encoding then; Motion vector r with each F macro block of present frame _i(x _i, y _i) convert one-dimensional sequence L to _Mv=(x ₁, y ₁, x ₂, y ₂...) after, with x ' ₄Carry out xor operation;

$L_{\mathrm{mv}}^{\′}=L_{\mathrm{mv}}\⊕x_4^{\′}---\left(7\right)$

After operation is finished, the motion vector of each macro block of present frame is carried out the Huffman coding, finish the encryption of P frame information;

Above-mentioned cryptographic algorithm embeds in the compression encoding process of MPEG, and decipherment algorithm is the inverse process of cryptographic algorithm, is reversible owing to encrypt engineering, according to the reverse order of ciphering process encrypted video stream is handled, and just can obtain decrypted video stream.

More than the 2nd the step described hyperchaotic system be the four-dimension hyperchaotic system, its model is as follows:

$\left\{\begin{array}{c}{\stackrel{\·}{x}}_1=a(x_2-x_1)+x_4\\ {\stackrel{\·}{x}}_2=d{x}_2-x_2{x}_3+c{x}_4\\ {\stackrel{\·}{x}}_3=x_1{x}_2-b{x}_3\\ {\stackrel{\·}{x}}_4=x_2{x}_3+r{x}_4\end{array}\right.---\left(8\right)$

X wherein ₁, x ₂, x ₃, x ₄Be state variable, a, b, c, d are parameters, work as a=35, b=3, c=12, d=7, during r=0.6, system is a hyperchaotic system.

Advantage of the present invention and good effect:

The present invention proposes a kind of mpeg video stream encryption method based on the hyperchaos sequence.This cryptographic algorithm combines stream encryption technology and block encryption technology; Respectively DC, the AC coefficient of I frame carried out xor operation, is that unit carries out the position scramble with the piece to the monochrome information of I frame based on the hyperchaos sequence; Motion vector to the P frame carries out xor operation; Because introduce hyperchaotic system as signal source, the key space of this encryption method is huge, uprising power attacking ability strengthens; Ciphering process embeds MPEG and gets in the compression encoding process, and algorithm has good real-time, and simultaneously, the introducing of internal key significantly strengthens the anti-plaintext attack ability of algorithm.This algorithm security height, real-time are good, and the real-time Transmission that is suitable for mpeg video stream is encrypted.

[description of drawings]

Fig. 1 is that mpeg video stream is encrypted schematic diagram.

Fig. 2 is a mpeg video stream I frame scrambled flow process.

Fig. 3 is a mpeg video stream P frame scrambled flow process.

Fig. 4 is the normal structure of MPEG.

Fig. 5 is cipher round results figure, the former video figure of A, and B encrypts rear video figure, C deciphering rear video figure.

[embodiment]

Embodiment 1:

Give an example below and realize

1, mpeg video stream I two field picture is divided into 8 * 8 segment, uses formula (1) that each segment is carried out discrete cosine transform, obtain AC, DC coefficient after the quantification;

2, get hyperchaotic system initial value x ₁(0)=x ₂(0)=x ₃(0)=x ₄(0)=0.1 as external key, hyperchaotic system is carried out iteration 200000 times, obtain hyperchaos sequence x with fourth-order Runge-Kutta method ₁, x ₂, x ₃, x ₄, utilize formula (3) hyperchaos sequence to carry out numerical value and handle, obtain x ' ₁, x ' ₂, x ' ₃, x ' ₄Calculate the m value according to formula (4), select the chaos sequence combination;

3, the k that calculates according to formula (6) changes the initial value of hyperchaotic system as internal key, obtains new hyperchaos sequence

4, utilize x ' ₁, x ' ₂, x ' ₃, x ' ₄Sequence is carried out xor operation to DC coefficient in the I frame, and the piece that the Y plane space is carried out with 8 * 8 is the space scramble of unit; Utilize sequence

The AC coefficient is carried out xor operation, then DC, AC coefficient after encrypting are encoded;

5, utilize x ' ₁, x ' ₂, x ' ₃, x ' ₄Motion vector to F macro block in the P frame carries out xor operation, then, the motion vector of each macro block is carried out the Huffman coding;

Operate according to above-mentioned step, be that a tested object is 128 * 128 the mpeg video stream in 6 seconds of length below, test platform CPU is a Pentium IV 1.7G processor, 2G internal memory, operating system are Windows XP, a fragment in the intercepting video, its cipher round results as shown in Figure 5, it is abundant to encrypt the rear video image scrambling as can be seen, can't reflect any information of original image, and cipher round results is good; Video image and original image after the correct deciphering are in full accord.

Claims (2)

1. Video stream information encryption method based on the hyperchaos sequence is characterized in that the concrete steps of this method are as follows:

1st, utilize I, P, the B frame structure features of MPEG, at first the I frame is encrypted; The I frame information is carried out dct transform, and as formula (1), it is that wherein, A (0,0) is the DC coefficient in 8 * 8 the matrix A that the coefficient of DCT is read in dimension, and all the other coefficients are the AC coefficient;

$F(u,v)=\frac{2}{N}C\left(u\right)C\left(v\right)\underset{x=0}{\overset{N-1}{\mathrm{\Σ}}}\underset{y=0}{\overset{N-1}{\mathrm{\Σ}}}f(x,y)\cos \frac{(2x+1)\mathrm{u\π}}{2N}\cos \frac{(2y+1)\mathrm{v\π}}{2N}---\left(1\right)$

In the formula, when u=v=0,

Work as u, v is not 0 o'clock entirely, and C (u)=C (v)=1;

2nd, select hyperchaotic system, and set its initial value x ₁(0), x ₂(0), x ₃(0), x ₄(0), adopts fourth-order Runge-Kutta method that hyperchaotic system is carried out iterative, in each iterative process, all can obtain 4 data and be x ₁(i), x ₂(i), x ₃(i), x ₄And then obtain 4 hyperchaos sequence x (i), ₁, x ₂, x ₃, x ₄, use formula (2) that 4 sequences are carried out numerical value then and handle,

x′ _j(i)＝mod((round(|x _j(i)|-floor|x _j(i)|)×10 ¹⁴)，256) (2)

In the formula, i=1,2,3 ... represent iteration the i time, j=1,2,3,4, mod () is a MOD function, and round () is a bracket function, and floor () is downward bracket function;

3rd, calculate the m value by formula (3), m ∈ [0,2] decides which group of selection to be used for encrypting by the m value;

m＝mod(x′ ₁(i)，3) (3)

m Combinations of states 0 {x′ ₁(i)，x′ ₂(i)，x′ ₃(i)} 1 {x′ ₁(i)，x′ ₂(i)，x′ ₄(i)} 2 {x′ ₂(i)，x′ ₃(i)，x′ ₄(i)}

If m=2, then select x ' ₂(i), x ' ₃(i), x ' ₄(i) } be used for encrypting, utilize x ' ₂Sequence is carried out the XOR cryptographic operation to DC coefficient sequence in the I frame, establishes that the DC coefficient sequence is L in the I frame _Dc, the DC coefficient sequence is L ' behind the xor operation _DcUtilize x ' ₃It is the position scramble of unit that the Y plane space is carried out with 8 * 8 block of pixels,

$L_{\mathrm{dc}}^{\′}=L_{\mathrm{dc}}\⊕x_2^{\′}---\left(3\right)$

In the formula,

The expression xor operation;

4th, the AC coefficient sequence of establishing non-zero in the I frame is L _Ac, its element number is n, the k that calculates according to formula (4) is as internal key,

$k=\frac{1}{256}(\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{L}_{\mathrm{ac}}\left(i\right),256)---\left(4\right)$

Utilize formula (5) to change the initial value of hyperchaotic system, and then, after formula (2) numerical value is handled, can obtain sequence of values based on the new hyperchaos sequence of hyperchaotic system generation

${\tilde{x}}_1\left(0\right)=x_1\left(0\right)+0.1\×k$

(5)

${\tilde{x}}_2\left(0\right)=x_2\left(0\right)+0.1\×k$

Intercepting

Preceding n data of sequence and L _AcCarry out xor operation, the sequence behind the xor operation is designated as L ' _Ac, as formula (6),

$L_{\mathrm{ac}}^{\′}=L_{\mathrm{ac}}\⊕{\tilde{x}}_1---\left(6\right)$

In the formula,

The expression xor operation; With L ' _AcCoefficient sequence is carried out the haul distance compressed encoding, with L ' then according to the ordering of Zig-Zag shape _DeCoefficient sequence is carried out differential pulse coding, all carries out the Huffman coding at last, finishes the encryption of I two field picture;

5th, for guaranteeing the fail safe of algorithm, select the motion vector of F macro block in the P frame to encrypt, establish two macro block M ₁And M ₂, coded image macro block M ₁Be reference picture macro block M ₂Best matching blocks, their difference is exactly the poor of respective pixel values in these two macro blocks, and the difference of gained is carried out color space transformation, and does 4: 1: 1 sampling and obtain Y, C _r, C _bComponent value carries out dct transform, quantification and variable-length encoding then; Motion vector r with each F macro block of present frame _i(x _i, y _i) convert one-dimensional sequence L to _Mv=(x ₁, y ₁, x ₂, y ₂...) after, with x ' ₄Carry out xor operation;

$L_{\mathrm{mv}}^{\′}=L_{\mathrm{mv}}\⊕x_4^{\′}---\left(7\right)$

After operation is finished, the motion vector of each macro block of P frame is carried out the Huffman coding, finish the encryption of P frame information;

Above-mentioned cryptographic algorithm embeds in the compression encoding process of MPEG, decipherment algorithm is the inverse process of cryptographic algorithm, because xor operation and position scramble process all are reversible, according to the reverse order of ciphering process encrypted video stream are handled, just the video flowing that can obtain deciphering.

2. method according to claim 1 is characterized in that described hyperchaotic system of the 2nd step is four-dimensional hyperchaotic system, and its model is as follows:

$\left\{\begin{array}{c}{\stackrel{\·}{x}}_1=a(x_2-x_1)+x_4\\ {\stackrel{\·}{x}}_2=d{x}_2-x_2{x}_3+c{x}_4\\ {\stackrel{\·}{x}}_3=x_1{x}_2-b{x}_3\\ {\stackrel{\·}{x}}_4=x_2{x}_3+r{x}_4\end{array}\right.---\left(8\right)$

X wherein ₁, x ₂, x ₃, x ₄Be state variable, a, b, c, d are parameters, work as a=35, b=3, c=12, d=7, during r=0.6, system is a hyperchaotic system.

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