CN103955883A - Asymmetric double-image encryption method based on fractional Fourier domain phase recovery procedure - Google Patents

Abstract

An asymmetric double-image encryption method based on a fractional Fourier domain phase recovery procedure comprises the steps of pure phase extraction, phase modulation and fractional Fourier transform. The asymmetric double-image encryption method based on the fractional Fourier domain phase recovery procedure is applied to double-image encryption, the encryption process is different from the decryption process, an encryption key is different from a decryption key, and the defects that a traditional symmetric encryption algorithm is easy to attack and an encryption key is the same as a decryption key are overcome. Through attack tests, it is proved that the method is high in resistance to violent attacks, noise attacks and other specific attacks. Meanwhile, key space is large, the problem that a traditional encryption algorithm is insufficient in key space is solved, the decryption process can be realized through an optical method, and a system is simple and convenient to operate.

Description

Asymmetric double image encryption method based on fractional Fourier domain phase place rejuvenation

Technical field

The invention belongs to virtual optics information ciphering method technical field, relate to a kind of asymmetric double image encryption method based on fractional Fourier domain phase place rejuvenation.

Background technology

Along with popularizing rapidly of internet, image has been widely used in various fields as the very efficient information carrier of contemporary society, and image encryption problem becomes an important field in information security field.From Refregier and Javidi propose classical based on double random phase, encrypt (DRPE) technology since, between the more than ten years, many encryption and Verification Systems based on Fourier transform domain, fractional Fourier transform domain, Fresnel territory, GT territory are proposed one after another in the past.And Alfalou and Brosseau point out: these technology can be used as squeeze operation simultaneously.Although the optical encryption systems based on DRPE issued of great majority for signal process have outstanding in processing power parallel, multidimensional.But we are noted that all these strategies all belong to the category of symmetric cryptosystem, encryption key is simultaneously as decruption key.Some research show: these strategies, due to linear properties intrinsic in their mathematics and optical transition, are easy under attack.For resisting these attacks, Qin and Peng propose a kind of asymmetric cryptosystem based on phase truncation Fourier transform (PTFT), the encryption key of this strategy is different from decruption key, by operate to avoid the linear properties of cryptographic system with nonlinear phase truncation.

Recently, since Situ state is extra large and Zhao Daomu proposes many image encryptions technology, the many image encryptions technology based on frequency multiplexing technique is more and more paid close attention at information security field.Alfalou and Mansour propose the encipherment scheme of two safe floors, and ground floor comes multiplexing and encrypts target image simultaneously by phase place rejuvenation, and the second layer is used double random phase system and carried out encrypted image.After work in, the people such as Alfalou utilize discrete cosine transform to compress and the work of encrypting multiple image simultaneously.Wang little Gang and Zhao Daomu propose the full phase image encipherment scheme based on superposition principle and hologram, and this scheme is encrypted to pure phase bit function (POF) by real-valued original image.Deng Xiaopeng and Zhao Daomu propose to use many image encryption methods of Fourier phase place rejuvenation and phase-modulation, and the method is avoided the impact of crosstalk noise completely.The people such as Hwang Hone-Ene propose in Fresnel territory the color image encryption scheme based on improved Gerchberg – Saxton algorithm (MGSA), reduce significantly the interference of crosstalk noise to image information.

Dual image is encrypted a special case as many image encryptions, has also attracted very large concern in optical encryption system.The dual image that Li Huijuan and Wang Yurong propose based on iteration Gyrator conversion is encrypted, with not on the same group Gyrator translation-angle two width original encryption are become to a width ciphertext graph picture simultaneously.The work that the people such as Li Huijuan do is two width images to be encrypted respectively to real part and the imaginary part of a complex function.The image encryption that two width wishs are encrypted that Wang little Gang and Zhao Daomu propose based on Phase Retrieve Algorithm and PTFT enters the image on bright, and encryption key is different from decruption key in the method.Yet, Wang little Gang and a kind of special attack of Zhao Daomu design, two step iteration amplitude restoration methods are used in this attack.Under this attack, when encryption key is during as PKI, enciphered message can be revealed.Subsequently, Wang little Gang and Zhao Daomu propose the another kind of a kind of dual image encryption technology that this attack is had to very strong repellence.Afterwards, Li Huijuan and Wang Yurong propose the dual image encryption technology based on discrete fraction stochastic transformation and chaotic maps, and this technology can improve the efficiency when encrypting, store, changing.The people such as Xiao Di propose the dual image optical encryption based on discrete Chirikov standard mapping, in the method, two width original images are respectively as amplitude and the phase place of complex function, use after this complex function of Chirikov standard mapping scramble, under the effect of the discrete fraction stochastic transformation based on chaos and 2 D chaotic random mask, obtain final ciphertext.Although above-mentioned algorithm has been simplified ciphering process to a certain extent, still there is the problems such as security is low, key space is little, speed of convergence is slow.

Summary of the invention

The object of the invention is to propose a kind of asymmetric double image encryption method based on fractional Fourier domain phase place rejuvenation, solve the security that prior art exists low, be vulnerable to the problem of attacking.

The technical solution adopted in the present invention is that the asymmetric double image encryption method based on fractional Fourier domain phase place rejuvenation, comprises pure phase extraction, phase-modulation, fractional fourier transform step.Specifically comprise the steps:

The first step, pure phase extraction: have two width original-gray image, use fractional Fourier domain phase place rejuvenation to extract i (i=1,2) width gray level image f _ipure phase bit function exp (the j ξ of (i=1,2) _{i, 1}) (i=1,2); Using fractional Fourier domain phase place rejuvenation extraction original-gray image f _iin the pure phase bit function process of (i=1,2), supervene phase mask function phi _{i, 1}, φ _{i, 2}, ξ _{i, 2}(i=1,2);

Second step, phase-modulation: in intermediate images generation module, a complex matrix H _i(i=1,2) by amplitude image as g and corresponding two phase function ξ _{i, 1}, ξ _{i, 2}produce

H _i＝F ^β2{F ^β1[gexp(jξ _i,1)]exp(jξ _i,2)} (1)

Carry out phase-modulation, two H _iby convolution algorithm, be combined into a matrix H

H=H ₁* H ₂(2) in formula (1), (2), j is the imaginary part of symbol, and exp{} is exponent arithmetic, and g is phase image, F ^αrepresent fractional fourier transform, ξ _{i, 1}, ξ _{i, 2}be phase function, H is modulation result, and * represents convolution algorithm;

The 3rd step, fractional fourier transform: the modulation result H that second step is obtained implements α ₃rank fractional fourier transform obtains calculate the amplitude of matrix be ciphertext C _final, decruption key φ _i,dalso generated simultaneously:

${\mathrm{\φ}}_{i,d}=\arg \left[\exp \left(j\arg \right\{F^{{\mathrm{\α}}_3}\left(H_i\right)\left\}\right)\frac{\left|F^{{\mathrm{\α}}_3}{H}_i\right|}{\left|H\right|}\right]---\left(3\right)$

Wherein, | H| represents the amplitude of combinatorial matrix, and j is the imaginary part of symbol, and exp{} is exponent arithmetic, the phase place of arg{} representing matrix.

Fractional Fourier domain phase place rejuvenation is used three phase place masterplate functions, φ _{i, 1}, φ _{i, 2}, ξ _{i, 1}, (i=1,2) are three phase place masterplate functions of this process;

The decrypting process of above-mentioned encryption method is specially, by final ciphertext C _finalbe multiplied by phase function exp (j φ _i,d) generation complex matrix right enforcement-(α ₂+ α ₃) result H after rank are modulated against fractional fourier transform _i, by H _iwith phasing matrix exp (j φ _{i, 2}) multiplying each other obtains h _i, to h _ienforcement-α ₁rank obtain against fractional fourier transform then extract amplitude as deciphering image f _i, that is:

f _i＝|F ^-α1{F ^-(α2+α3)[C _finalexp(jφ _i,d)]}expj(φ _i,2)| (4)

Above-mentioned decryption method decryption device used comprises two spatial light modulators and two lens, and two spatial light modulators and two lens are spaced; Two spatial light modulators are spatial light modulator PM1 and spatial light modulator PM2, and two lens are lens L1 and lens L2; Lens L1 is arranged between spatial light modulator PM1 and spatial light modulator PM2, lens L2 is arranged on spatial light modulator PM2 between deciphering image, spatial light modulator PM1 is connected with electronic controller with spatial light modulator PM2, and electronic controller is connected with deciphering image by computing machine.

Spatial light modulator PM1 and spatial light modulator PM2 are set to respectively to exp (j φ _i,d) and exp (j φ _{i, 2}), decrypting process is with ciphertext image C _finalas incident light input, usage space photomodulator PM1 modulation ciphertext image C _final, the image of modulation sees through lens L1 realization-(α ₂+ α ₃) rank fractional fourier transform; Usage space photomodulator PM2 modulation-(α ₂+ α ₃) result of rank fractional fourier transform, the image after modulation sees through lens L2 realization-α ₁rank fractional fourier transform, can obtain original plaintext image f _i.

Above-mentioned decryption method also can realize with PMD, and PMD comprises two masks and two lens, and two masks and two lens are spaced; Two masks are mask exp (j φ _i,d) and mask exp (j φ _{i, 2}), two lens are lens L1 and lens L2; Lens L1 is arranged on mask exp (j φ _i,d) and mask exp (j φ _{i, 2}) between, lens L2 is arranged on mask mask exp (j φ _{i, 2}) and decipher between image mask exp (j φ _i,d) and mask exp (j φ _{i, 2}) be connected with electronic controller, electronic controller is connected with ccd image sensor by computing machine, by obtaining deciphering image on CCD.

The present invention has following beneficial effect:

1, ciphering process of the present invention is different from decrypting process, and encryption key is different from decruption key, has avoided identical with decruption key, the pregnable shortcoming of rivest, shamir, adelman encryption key, has improved security.

2, by attack test, prove that the present invention is not only strong for the resistibility of brute force attack, and also very strong for the resistibility of noise and other particular attack.Disabled user cannot be by attacking any valuable information of Image Acquisition.

3, encryption method of the present invention has solved the little problem of existing encryption system key space, has improved key space.By statistical study, for key φ _i,d, key space is about S ₁≈ 116 ^{256 * 256}; φ _{i, 2}key space be about S ₁≈ 6 ^{256 * 256}.Because the key space of encryption system is S ₁* S ₂, therefore, the present invention has the enough large key spaces that are enough to oppose violence and attack.

4, encryption method of the present invention has improved speed of convergence simultaneously.The convergence number of times of existing single channel encryption method is 400 left and right, and the convergence number of times of encryption method of the present invention is approximately 40 times, and speed of convergence is significantly improved.

5, decrypting process of the present invention can be realized by optical means, and system is simple, easy to operate.

Accompanying drawing explanation

Fig. 1 is the asymmetric double image encryption method schematic diagram that the present invention is based on fractional Fourier domain phase place rejuvenation.

Fig. 2 is the asymmetric double image encryption method ciphering process figure that the present invention is based on fractional Fourier domain phase place rejuvenation.

Fig. 3 is the asymmetric double image encryption method decrypting process figure that the present invention is based on fractional Fourier domain phase place rejuvenation.

Fig. 4 is the asymmetric double image decryption square law device structural representation that the present invention is based on fractional Fourier domain phase place rejuvenation.

Fig. 5 adopts to the present invention is based on the original image " Zelda " that the asymmetric double image decryption method of fractional Fourier domain phase place rejuvenation is encrypted.

Fig. 6 adopts to the present invention is based on the original image " Peppers " that the asymmetric double image decryption method of fractional Fourier domain phase place rejuvenation is encrypted.

Fig. 7 adopts the ciphertext graph picture obtaining after the asymmetric double image encryption method encryption that the present invention is based on fractional Fourier domain phase place rejuvenation.

Fig. 8 adopts the decruption key φ the present invention is based on the image " Zelda " that the asymmetric double image decryption method of fractional Fourier domain phase place rejuvenation is encrypted _{i, 2}.

Fig. 9 adopts the decruption key φ the present invention is based on the image " Zelda " that the asymmetric double image decryption method of fractional Fourier domain phase place rejuvenation is encrypted _i,d.

Figure 10 adopts to the present invention is based on the image that the asymmetric double image decryption method of fractional Fourier domain phase place rejuvenation is encrypted " Peppers " decruption key φ _{i, 2}.

Figure 11 adopts to the present invention is based on the image that the asymmetric double image decryption method of fractional Fourier domain phase place rejuvenation is encrypted " Peppers " decruption key φ _i,d.

Figure 12 adopts the deciphering image the present invention is based on the image " Zelda " that the asymmetric double image decryption method of fractional Fourier domain phase place rejuvenation is encrypted.

Figure 13 adopts the deciphering image the present invention is based on the image " Peppers " that the asymmetric double image decryption method of fractional Fourier domain phase place rejuvenation is encrypted.

Embodiment

Below in conjunction with the drawings and specific embodiments, the present invention is described in detail.

Asymmetric double image encryption method based on fractional Fourier domain phase place rejuvenation, comprises pure phase extraction, phase-modulation, fractional fourier transform; Concrete steps are as follows:

The first step, pure phase extraction: have two width original-gray image, use fractional Fourier domain phase place rejuvenation to extract i (i=1,2) width gray level image f _ithe pure phase bit function ξ of (i=1,2) _{i, 1}(i=1,2); Using fractional Fourier domain phase place rejuvenation extraction original-gray image f _iin the pure phase bit function process of (i=1,2), supervene phase mask function phi _{i, 1}, φ _{i, 2}, ξ _{i, 2}(i=1,2);

Second step, phase-modulation: in intermediate images generation module, a complex matrix H _i(i=1,2) by amplitude image as g and corresponding two phase function ξ _{i, 1}, ξ _{i, 2}produce

H _i＝F ^β2{F ^β1[gexp(jξ _i,1)]exp(jξ _i,2)} (1)

Carry out phase-modulation, two H _iby convolution algorithm, be combined into a matrix H

H＝H ₁*H ₂ (2)

In formula (1), (2), j is the imaginary part of symbol, and exp{} is exponent arithmetic, and g is phase image, F ^αrepresent fractional fourier transform, ξ _{i, 1}, ξ _{i, 2}be phase function, H is modulation result, and * represents convolution algorithm;

The 3rd step, fractional fourier transform: the modulation result H that second step is obtained implements α ₃rank fractional fourier transform obtains calculate the amplitude of matrix | be ciphertext C _final, decruption key φ _i,dalso generated simultaneously:

${\mathrm{\φ}}_{i,d}=\arg \left[\exp \left(j\arg \right\{F^{{\mathrm{\α}}_3}\left(H_i\right)\left\}\right)\frac{\left|F^{{\mathrm{\α}}_3}{H}_i\right|}{\left|H\right|}\right]---\left(3\right)$

Wherein, | H| represents the amplitude of combinatorial matrix, and j is the imaginary part of symbol, and exp{} is exponent arithmetic, the phase place of arg{} representing matrix.

Fractional Fourier domain phase place rejuvenation is used three phase place masterplate functions, φ _{i, 1}, φ _{i, 2}, ξ _{i, 1}, (i=1,2) are three phase place masterplate functions of this process.

The decrypting process of above-mentioned encryption method is specially, by final ciphertext C _finalbe multiplied by phase function exp (j φ _i,d) generation complex matrix right enforcement-(α ₂+ α ₃) result H after rank are modulated against fractional fourier transform _i, by H _iwith phasing matrix exp (j φ _{i, 2}) multiplying each other obtains h _i, to h _ienforcement-α ₁rank obtain against fractional fourier transform then extract amplitude as deciphering image f _i, that is:

f _i＝|F ^-α1{F ^-(α2+α3)[C _finalexp(jφ _i,d)]}expj(φ _i,2)| (4)

The principle of work of encryption method of the present invention is: first, the asymmetric double image encryption method of use based on fractional Fourier domain phase place rejuvenation extracts the pure phase bit function of every width image in two width original-gray image.Then, utilize convolution algorithm by two width image integrations in piece image.Finally, exchange the result making and implement a α ₃rank fractional fourier transform, the amplitude that extracts the rear result of conversion obtains final ciphertext.Meanwhile, in ciphering process, decruption key also produces in the lump.

Encryption method principle of the present invention is referring to Fig. 1, (x _i, y _i) and (x _o, y _o) represent respectively to input and output coordinate.And conversion core is as follows:

K(x _i,y _i；x _o,y _o)＝A _φexp{iπ[(x _i ²+y _i ²+x _o ²+y _o ²)cotφ _α-2(x _ix _o+y _iy _o)cscφ _α]}

(5)

$A_{\mathrm{\φ}}=\frac{\exp [-\mathrm{i\πsgn}\left(\sin {\mathrm{\φ}}_{\mathrm{\α}}\right)/2+i{\mathrm{\φ}}_{\mathrm{\α}}]}{\left|\sin {\mathrm{\φ}}_{\mathrm{\α}}\right|}---\left(6\right)$

φ _α＝απ/2 (7)

Ciphering process of the present invention, referring to Fig. 2, first, extracts the pure phase bit function of the every width image of two width original-gray image.Detailed process: use fractional Fourier domain phase place rejuvenation to extract i width gray level image f _ipure phase bit function ξ _{i, 1}, φ _{i, 1}, φ _{i, 2}, ξ _{i, 2}for extracting the phase mask function of supervening in the pure phase bit function process of i width original-gray image, i=1 wherein, 2.α ₁, α ₂, α ₃, β ₁, β ₂fractional exponent for iterative phase rejuvenation.Secondly, to obtain two H _i(i=1,2), utilize convolution algorithm to calculate H.Then, by relevant fractional exponent α ₁, α ₂, α ₃, β ₁, β ₂set.The result H that second step is obtained implements α ₃rank fractional fourier transform obtains the amplitude of compute matrix be ciphertext C _final, decruption key φ _i,daccording to formula, also generated simultaneously.

Deciphering is the inverse process of encrypting.Decrypting process of the present invention, referring to Fig. 3, is specially, by final ciphertext C _finalbe multiplied by phase function exp (j φ _i,d) generation complex matrix right enforcement-(α ₂+ α ₃) result H after rank are modulated against fractional fourier transform _i, by H _iwith phasing matrix exp (j φ _{i, 2}) multiplying each other obtains h _i, to h _ienforcement-α ₁rank obtain against fractional fourier transform then extract amplitude as deciphering image f _i,

f _i＝|F ^-α1{F ^-(α2+α3)[C _finalexp(jφ _i,d)]}expj(φ _i,2)| (4)

Fig. 4 is the structural representation that the present invention is based on the asymmetric double image decryption method equipment therefor of fractional Fourier domain phase place rejuvenation.This device is similar to the 4f imaging system of DRPE, comprises two spatial light modulators and two lens, and two spatial light modulators and two lens are spaced.In the embodiment of the present invention, two spatial light modulators are spatial light modulator PM1 and spatial light modulator PM2, and two lens are lens L1 and lens L2.Lens L1 is arranged between spatial light modulator PM1 and spatial light modulator PM2, and lens L2 is arranged on spatial light modulator PM2 between deciphering image, and PM1 is connected with electronic controller with PM2, and electronic controller is connected with CCD image sensor by computing machine.PM1 and PM2 are set to respectively to exp (j φ _i,d) and exp (j φ _{i, 2}), decrypting process is with ciphertext image C _finalas incident light input, usage space photomodulator PM1 modulation ciphertext image C _final, the image of modulation sees through lens L1 realization-(α ₂+ α ₃) rank fractional fourier transform; Usage space photomodulator PM2 modulation-(α ₂+ α ₃) result of rank fractional fourier transform, the image after modulation sees through lens L2 realization-α ₁rank fractional fourier transform can obtain the plaintext image f decrypting on CCD _i.

Above-mentioned encryption method also can realize with PMD, is similar to the 4f imaging system of DRPE, in ciphering process, just PM1 and PM2 is replaced to phase mask exp (j φ _i,d) and exp (j φ _{i, 2}).

In the present invention, by correlation coefficient (CC) or mean square deviation (MSE) as phase place rejuvenation iteration ending standard, when CC is greater than of preset in advance, approaches 1 value or mean square deviation MSE value and be less than of preset in advance and approach 0 value, iteration stops, and the computing formula of CC and MSE is as follows:

$\mathrm{CC}=\frac{E\left\{\right[g-E\left(g\right)\left]\right[g^k-E\left(g^k\right)\left]\right\}}{\sqrt{E\left\{{[g-E\left(g\right)]}^2\right\}}\sqrt{E\left\{{[g^k-E\left(g^k\right)]}^2\right\}}}---\left(8\right)$

$\mathrm{MSE}=\frac{\underset{0}{\overset{M-1}{\mathrm{\Σ}}}\underset{0}{\overset{N-1}{\mathrm{\Σ}}}{[g-g^k]}^2}{M\×N}---\left(9\right)$

Wherein, g is plaintext image, g ^kfor the approximate plaintext image that iteration obtains, M, N is respectively expressly width and the height of image, E[] be expectation value compute sign.Suppose that last iterations is K, best phase function is:

φ ₁＝φ ₁ ^K,φ ₂＝φ ₂ ^K,ξ ₁＝ξ ₁ ^K- ¹,ξ ₂＝ξ ₂ ^K (10)

" Zelda " in Fig. 5, Fig. 6 and " Peppers " and the ciphertext graph picture that obtains after encrypting of original image as shown in Figure 7, ciphertext graph looks like to present fixing white noise and distributes, and only containing strength information, image cannot provide any valuable information for disabled user.Visible, encryption method of the present invention to add density very high.

Image " Zelda " decruption key φ _{i, 2}referring to Fig. 8, can find out, decruption key is similar to white noise and distributes.

Image " Zelda " decruption key φ _i,dreferring to Fig. 9, can find out, decruption key is similar to white noise and distributes.

Image " Peppers " decruption key φ _{i, 2}referring to Figure 10, can find out, decruption key is similar to white noise and distributes.

Image " Peppers " decruption key φ _i,dreferring to Figure 11, can find out, decruption key is similar to white noise and distributes.

The image decrypting " Zelda " is referring to Figure 12, comparison diagram 5 Central Plains figure " Zelda " with decrypt " Zelda " image, can find out that deciphering image and original image almost do not have error.

The image decrypting " Peppers " is referring to Figure 13, comparison diagram 6 Central Plains figure " Peppers " with decrypt " Peppers " image, can find out that deciphering image and original image almost do not have error.

Encryption method of the present invention has solved the little problem of existing encryption system key space, has improved key space.By statistics, for key φ _i,d, key space is about S ₁≈ 116 ^{256 * 256}; φ _{i, 2}key space be about S ₁≈ 6 ^{256 * 256}.Because the key space of encryption system is S ₁* S ₂, therefore, the present invention has the enough large key spaces that are enough to oppose violence and attack.

Encryption key of the present invention is different from decruption key, has avoided identical with decruption key, the pregnable shortcoming of rivest, shamir, adelman encryption key, has improved security.

By attack test, prove that the present invention is not only strong for the resistibility of brute force attack, and also also very strong for the resistibility of noise and other particular attack.Disabled user cannot be by attacking any valuable information of Image Acquisition.

Decrypting process of the present invention can be realized by optical means, and system is simple, easy to operate.

Claims (7)

1. the asymmetric double image encryption method based on fractional Fourier domain phase place rejuvenation, is characterized in that, comprises pure phase extraction, phase-modulation, fractional fourier transform step.

2. the asymmetric double image encryption method based on fractional Fourier domain phase place rejuvenation as claimed in claim 1, is characterized in that ciphering process is different from decrypting process, and encryption key is different from decruption key, specifically comprises the steps:

The first step, pure phase extraction: have two width original-gray image, use fractional Fourier domain phase place rejuvenation to extract i width gray level image f _ithe pure phase bit function ξ of (i=1,2) _{i, 1}(i=1,2); Using fractional Fourier domain phase place rejuvenation extraction original-gray image f _iin the pure phase bit function process of (i=1,2), supervene phase mask function phi _{i, 1}, φ _{i, 2}, ξ _{i, 2}(i=1,2);

Second step, phase-modulation: in intermediate images generation module, a complex matrix H _iby amplitude image as g and corresponding two phase function ξ _{i, 1}, ξ _{i, 2}produce

H _i＝F ^β2{F ^β1[gexp(jξ _i,1)]exp(jξ _i,2)} (1)

Carry out phase-modulation, two H _iby convolution algorithm, be combined into a matrix H

H＝H ₁*H ₂ (2)

In formula (1), (2), j is the imaginary part of symbol, and exp{} is exponent arithmetic, and g is phase image, F ^αrepresent fractional fourier transform, ξ _{i, 1}, ξ _{i, 2}be phase function, H is modulation result, and * represents convolution algorithm;

The 3rd step, fractional fourier transform: the result H that second step is obtained implements α ₃rank fractional fourier transform obtains be ciphertext C _final, decruption key φ _i,dalso generated simultaneously:

Wherein, | H| represents the amplitude of combinatorial matrix, and j is the imaginary part of symbol, and exp{} is exponent arithmetic, the phase place of arg{} representing matrix.

3. the asymmetric double image encryption method based on fractional Fourier domain phase place rejuvenation as claimed in claim 2, is characterized in that: described fractional Fourier domain phase place rejuvenation is used three phase place masterplate functions, φ _{i, 1}, φ _{i, 2}, ξ _{i, 1}(i=1,2) are three phase mask functions of this process.

4. the asymmetric double image encryption method based on fractional Fourier domain phase place rejuvenation as described in claim 1-3 any one, is characterized in that, its decrypting process is specially: by final ciphertext C _finalbe multiplied by phase function exp (j φ _i,d) generation complex matrix right enforcement-(α ₂+ α ₃) result H after rank are modulated against fractional fourier transform _i, by H _iwith phasing matrix exp (j φ _{i, 2}) multiplying each other obtains h _i, to h _ienforcement-α ₁rank obtain against fractional fourier transform then extract amplitude as deciphering image f _i, that is:

f _i＝|F ^-α1{F ^-(α2+α3)[C _finalexp(jφ _i,d)]}expj(φ _i,2)| (4)

Wherein, j is the imaginary part of symbol, and exp{} is exponent arithmetic, C _finalrepresent final ciphertext of encrypting, F ^αrepresent fractional fourier transform.

5. the asymmetric double image decryption method based on fractional Fourier domain phase place rejuvenation as claimed in claim 4, it is characterized in that: decryption device used comprises two spatial light modulators and two lens, two spatial light modulators and two lens are spaced; Two spatial light modulators are spatial light modulator PM1 and spatial light modulator PM2, and two lens are lens L1 and lens L2; Lens L1 is arranged between spatial light modulator PM1 and spatial light modulator PM2, lens L2 is arranged on spatial light modulator PM2 between deciphering image, spatial light modulator PM1 is connected with electronic controller with spatial light modulator PM2, electronic controller is connected with ccd image sensor by computing machine, by obtaining deciphering image on CCD.

6. the asymmetric double image decryption method based on fractional Fourier domain phase place rejuvenation as claimed in claim 5, is characterized in that: spatial light modulator PM1 and spatial light modulator PM2 are set to respectively to exp (j φ _i,d) and exp (j φ _{i, 2}), decrypting process is with ciphertext image C _finalas incident light input, usage space photomodulator PM1 modulation ciphertext image C _final, the image of modulation sees through lens L1 realization-(α ₂+ α ₃) rank fractional fourier transform; Usage space photomodulator PM2 modulation-(α ₂+ α ₃) result of rank fractional fourier transform, the image after modulation sees through lens L2 realization-α ₁rank fractional fourier transform, can obtain the plaintext image f decrypting _i.

7. the asymmetric double image decryption method based on fractional Fourier domain phase place rejuvenation as claimed in claim 4, it is characterized in that: decryption device is PMD, PMD comprises two masks and two lens, and two masks and two lens are spaced; Two masks are mask exp (j φ _i,d) and mask exp (j φ _{i, 2}), two lens are lens L1 and lens L2; Lens L1 is arranged on mask exp (j φ _i,d) and mask exp (j φ _{i, 2}) between, lens L2 is arranged on mask mask exp (j φ _{i, 2}) and decipher between image mask exp (j φ _i,d) and mask exp (j φ _{i, 2}) be connected with electronic controller, electronic controller is connected with ccd image sensor by computing machine, by obtaining deciphering image on CCD.