CN105761198B - The compound image selection encryption and decryption approaches of a kind of dynamic probability and null tone domain - Google Patents

Abstract

The present invention provides a kind of dynamic probability and null tone domain compound image selection encryption and decryption approaches, by the compound crash-protective characteristics to improve list Hash feature of image MD5 value to be encrypted and SHA-1 value, divided by generating intermediate key parameter with user key close coupling for probability interval, probability generates, block of pixels to be encrypted is screened and determines probability encryption event and transformation parameter.Designed encrypted event includes airspace and frequency domain replacement operator to improve encryption efficiency and frequency coefficient is avoided to overflow the influence to visual quality of images is restored, mentioned method treats the encrypted feature of encrypted image and user key is all updated, so that the key parameters under different encryption numbers are very different simultaneously again with characteristics of image to be encrypted and user key tight association, while it can pass through that preset encryption threshold value carries out visual quality of images and frequency domain is overflowed to screen and be controlled again.In decryption, intermediate key collection need to be restored first, then reverse decryption oprerations are executed to the block of pixels filtered out.

Description

The compound image selection encryption and decryption approaches of a kind of dynamic probability and null tone domain

Technical field

The invention belongs to information securities and digital image signal process crossing research field, are related to a kind of image encryption reconciliation Decryption method, the in particular to compound image selection encryption and decryption approaches of a kind of dynamic probability and null tone domain.

Background technique

Traditional images encryption generally directed to be entire image, it is changed beyond recognition with secret for being converted to entire image Figure, not only brings high calculating cost, also masks all features of the image to be encrypted almost in addition to size.Very much It in practical application, is often not required to encrypt entire image, and only needs bit plane, region and the part picture selected to image Element is encrypted, and encryption while need to provide the Partial Feature of original image come to potential user more to experience, To exchange bigger commercial interest for, and the characteristics of image that these encrypted images are retained, can be further used for image classification, Retrieval and identification etc. have more use value to encrypt relative to traditional images.This bit that only image is selected The method that plane, region and partial pixel encrypt, referred to as selective encryption.

It encrypts for selective image, mainly has than more typical selective image encryption method at present:

1. the partial bit plane or bit to selection carry out selective encryption.For example, Rehman A U, 2015. (Rehman A U,Liao X,Kulsoom A,et al.Selective encryption for gray images based on chaos and DNA complementary rules[J].Multimedia Tools and Applications, 2015,74 (13): 4655-4677) it treats the high-low-position bit plane of encrypted image and is encrypted by different DNA sequence dnas. Kulsoom A,2016.(Kulsoom A,Xiao D,Aqeel-ur-Rehman,et al.An efficient and noise resistive selective image encryption scheme for gray images based on chaotic maps and DNA complementary rules[J].Multimedia Tools and Applications,2016,75 (1): 1-23. it is further introduced into the MD5 value of image) to improve Rehman A U, the anti-chosen -plain attact of 2015 strategies Ability.Moon D,2006.(Moon D,Chung Y,Pan S B,et al.An efficient selective encryption of fingerprint images for embedded processors[J].ETRI journal, 2006,28 (4): 444-452.) using the LSB of pixel as random keystream and high order bit position carry out exclusive or encryption cover to Encrypted image feature, and improve by secrecy LSB the safety of the strategy.Vanogenbroeck M,2002. (Vanogenbroeck M,Benedett R.Techniques for a selective encryption of uncompressed and compressed images[C]//in Proceedings of Advanced Concepts For Intelligent Vision Systems (ACIVS) 2002.2002:90-97.) it is random using 2 values big with close figure etc. The selected bit plane of key pair carries out exclusive or by turn and encrypts.Zhong Ming, 2008. (Zhong Ming, Liao Xiaofeng, Zhou Qing one kind be based on four fork The spatial domain picture of tree selects Encryption Algorithm [J] computer engineering, 2008,34 (18): 174-178.) bit of selecting image Plane is divided into 8 × 8 fritters, and the position of node is decomposed by the positional relationship and exchange 8 × 8 fritters 4 fork tree same layer that change fritter Sequence is set to encrypt to selected bit plane.Xiang T,2007.(Xiang T,Wong K,Liao X.Selective image encryption using a spatiotemporal chaotic system[J].Chaos: An Interdisciplinary Journal of Nonlinear Science, 2007,17 (2): 415-427.) use base Selective encryption is carried out to the bit plane chosen in 1 dimension coupled map lattices of skew tent map, and by adjusting to be encrypted Significant bit plane quantity compromise in safety and encryption performance.Hoang T,2014.(Hoang T,Tran, D.Cryptanalysis and security improvement for selective image encryption[J] .European Physical Journal Special Topics, 2014,223 (8): 1635-1646.) to Xiang T, 2007 safety is analyzed, and improves the strategy by changing the significant number of bits of each pixel participation encryption Safety.Rehman A U, 2015, Kulsoom A, 2016, Moon D, 2006, Vanogenbroeck M, 2002, Zhong Ming, 2008, Xiang T, 2007 and Hoang T, 2014 are all based on the selective image encryption of bit plane or bit.It is different Be Rehman A U, 2015 and Kulsoom A, 2016 pairs of high-low-position bit planes use different encryption policies；Moon D, 2006 be using low-order bit plane as the key encrypted to high order bit plane exclusive or；Vanogenbroeck M, 2002, Zhong Ming, 2008 and Xiang T, 2007 are encrypted to the bit plane chosen；Hoang T, 2014 pairs of different pixels into The bit bit encryption of row different number.Selective encryption strategy based on bit plane and bit can be by adjusting the ratio of encryption The quantity of special plane and encrypting bit position tends to tradition if encryption amount is excessive to adjust the visual quality of image to be encrypted Image encryption loses the identification feature of image if only encrypting to significant position or significant plane, if only to not significant bit Plane encryption, then can not be effectively reduced the visual quality of image.If being easy to brokenly in transmission process using LSB as key It is bad, cause encrypted image that can not restore.For gray scale or color image, only limited alternative bit plane passes through Different bit planes is selected to regulate and control the visual quality of image encryption cost and encrypted image, the regulation that can be played It acts on extremely limited.

2. screening to image pixel and block of pixels, selective encryption is carried out to the pixel and block of pixels filtered out.Example Such as, Zhao Liang, 2010. (Zhao Liang, Liao Xiaofeng, to the such as great waves based on Z matrix map and select encryption color image degeneration algorithm grind Study carefully Acta Physica Sinica [J], 2010,59 [3]: 1507-1523.) it gives based on pixel random screening template and Pixel Information entropy Image degeneration encryption method.Lin Yangfei, a kind of 2015. (encryption method of medical image data selectivity of Lin Yangfei, Ye Shaozhen Application of electronic technology [J], 2015,41 (3): 107-110.) using image block pixel and to carry out the block of pixels of encryption Screening, encrypts the block of pixels filtered out by SCAN language and image hash value.Wen W,2015.(Wen W,Zhang Y,Fang Z,et al.Infrared target-based selective encryption bychaotic maps[J] .Optics Communications, 2015,341:131-139.) utilize geometric active contour and partial differential equation to infrared figure The target area of picture is screened, and is then encrypted to the block of pixels filtered out.Khashan O A,2014.(Khashan O A,Zin A M,Sundararajan E A.Performance study of selective encryption in comparison to full encryption for still visual images[J].Journal of Zhejiang University SCIENCE C, 2014,15 (6): 435-444.) pixel and root are calculated to the not overlap partition that image divides The block of pixels of blowfish encryption is filtered out according to the relationship between pixel and given threshold.Zhang T,2013.(Zhang T, El-Latif A,Han Q,et al.Selective Encryption for Cartoon Images[C]// Intelligent Human-Machine Systems and Cybernetics(IHMSC),2013 5th International Conference on.IEEE, 2013,2:198-201.) utilize the screening card release of scalable Shape context Important information block to be encrypted in logical image.Ayoup A M,2015.(Ayoup A M,Hussein A H,Attia M A A.Efficient selective image encryption[J].Multimedia Tools and Applications, AES encryption 2015:1-16.) is carried out to the comentropy largest block filtered out.Mehta G,2014.(Mehta G,Dutta M K, Travieso-Gonzalez C M,et al.Edge based selective encryption scheme for biometric data using chaotic theory[C]//Contemporary Computing and Informatics (IC3I), 2014International Conference on.IEEE, 2014:383-386.) only to edge It detects the significant block filtered out to be encrypted, and significant block and non-significant piece is distinguished by encryption vector.Zhao Liang, 2010, Wen W, 2015, the Khashan O A M of A, 2014, Mehta G, 2014, Zhang T, 2013, Ayoup, 2015 Hes Mehta G, 2014 be all to carry out selective encryption to the pixel and block of pixels filtered out on image, need to set screening in screening Threshold value filters out corresponding pixel and block of pixels, since encryption front and back block of pixels does not usually correspond to, to keep encryption policy Restorability need to generally guarantee that encryption screening feature does not change or by recording and being embedded in encryption parameter come to encryption and not The pixel and block of pixels of encryption distinguish.For the former, it is usually only capable of the fixed encrypted feature of selection, such as comentropy or only It can guarantee that encrypted feature does not change using simple encryption policy；For the latter, it is usual to store additional encryption parameter Need higher storage cost.

3. carrying out selective encryption to the sensitizing range that user selectes.Ravishankar K C,2006. (Ravishankar K C,Venkateshmurthy M G.Region based selective image encryption [C]//Computing&Informatics,2006.ICOCI'06.International Conference on.ieee, 2006:1-6.) sensitizing range for selecting user is divided into nonoverlapping fritter, selects the fritter comprising sensitizing range Property encryption.Ou Y,2007.(Ou Y,Sur C,Rhee K H.Region-based selective encryption for medical imaging[M]//Frontiers in Algorithmics.Springer Berlin Heidelberg, 2007:62-73.) specify sensitizing range to carry out AES decryption user.Ravishankar K C, 2006 and Ou Y, 2007 are all Selective encryption is carried out to the area-of-interest that user selectes, in decryption, sensitizing range selected in advance need to be provided, thus Bring additional storage cost.

4. carrying out selective encryption to the specific frequency coefficient of image.Wang Lihua, 2010. (Wang Lihua, Liao Xiaofeng, Xiang Tao Equal image of the based on wavelet transformation is manually degenerated algorithm [J] computer engineering, 2010,36 (16): 203-207.) by original graph Wavelet field subgraph as being converted to different frequency ingredient, by adding multiplicative noise and additive noise to high frequency section come to figure As carrying out frequency domain selective encryption.Nidhi Taneja,2011.(Nidhi Taneja,Balasubramanian Raman, Indra Gupta.Selective image encryption in fractionalwavelet domain[J].AEU- International Journal of Electronics and Communications,2011,65(4):338-344.) In Fourier Transform of Fractional Order domain, the displacement of the position Arnold is carried out to the sub-band that energy component is greater than threshold value and exclusive or encrypts. Wang Lihua, 2010 and Nidhi Taneja, 2011 be all to convert image to frequency domain, and specific frequency coefficient is selected to be added Close, in frequency domain, visual quality of images can effectively be regulated and controled by choosing the different frequency coefficient of significance level, but simultaneously to frequency coefficient Encryption can also change the amplitude area of frequency coefficient, overflow and fail to decrypt correctly so as to cause airspace pixel.

In addition to the above problems, the selective image encryption safety problem existing there is also traditional images encryption, example If replaced and the loose coupling of process of obfuscation, the problems such as specific encryption policy is unrelated with image to be encrypted.

Summary of the invention

Present invention aims to overcome that prior art defect, provide a kind of dynamic probability and null tone domain compound image selection Property encryption and decryption approaches, designed encrypted event includes airspace and frequency domain replacement operator to improve encryption efficiency and avoid frequency Domain coefficient overflows the influence to visual quality of images is restored, while can be by preset encryption threshold value to visual quality of images It is controlled.

To achieve the above object, the invention adopts the following technical scheme:

The compound image selection encryption method of a kind of dynamic probability and null tone domain, comprising the following steps:

Step 1: remember that image to be encrypted is A=(a_i,j)_m×nAnd a_i,j∈ 0,1 ..., 255 }, i=0,1 ..., m-1, j=0, 1 ..., n-1, setting encryption number t, t > 0, primary iteration control parameter k=1, select initial parameter μ₀∈ [3.57,4] and Setting encryption judgment threshold δ, δ > 0, remember the MD5 value of A and SHA-1 value are respectively 16 system Number Sequence S_MD5=< m₀,m₁,…,m₃₁ > and S_SHA-1=< s₀,s₁,…,s₃₉>, by S_MD5And S_SHA-1Series connection is 16 system Number Sequence S_ms=S_MD5||S_SHA-1=< sm_i>₇₂,i =0,1 ..., 71 and initialization encryption event subscript index sequence S_idFor S_id=<0,1 ..., 5>, wherein " | | " it is bit bit string Serial operation symbol；

Step 2: by S_msIt is mapped as 16 system sequence S_h=< h₀,h₁,…,h₃₉>；

Step 3: by S_hIt is divided intoThen four parts willBe converted to (0,1) 10 system decimal G in range_i, i=0,1 ..., 3；

Step 4: by G₃As parameter alpha, G₀,G₁,G₂10 system decimal G being mapped as in (0,1) range₀′,G₁′,G₂', By G₀′,G₁′,G₂' it is used as key parameter X_init,Y_init,x_init, i.e. X_init=G₀′,Y_init=G₁′,x_init=G₂′；

Step 5: by initial parameter μ₀As system parameter, key parameter x_init5 (0,1) ranges are generated as initial value Interior random number is as sequence S_p=< p₀,p₁,p₂,p₃,p₄>, by S_pConstruct the interval division sequence S ' in (0,1) range_p=< p′₀,p₁′,p′₂,p′₃,p′₄>, to obtain probability interval [0, p '₀),[p₀′,p₁′),[p₁′,p₂′),[p₂′,p₃′),[p₃′, p₄′),[p₄′,1]；

Step 6: by key parameter Y_init,μ₀It is mapped as μ₁∈ [3.57,4], by X_initAnd μ₁Respectively as initial value and it is Parameter iteration of uniting generates the intermediate key parameter Z in (0,1) range_init；

Step 7: by X_init,Y_init,Z_initAs initial value, 3 real value random numbers of iteration 1 time generation are successively used as parameter X₀,Y₀,Z₀；

Step 8: by X₀,Y₀It is mapped as image A=(a to be encrypted_i,j)_m×nOn random point (r₀,v₀)；

Step 9: by (r₀,v₀) it is used as starting point, from image A=(a to be encrypted_i,j)_m×nFilter out M_in=(m_u,w)_4×4, calculate M_inMapping value Map (M_in), if Map (M_in) >=δ then executes step 10, on the contrary by x_initAs probabilistic determination value P, by X₀,Y₀, Z₀Mapping value as transformation parameter v, according to the P probability interval fallen into and S_id, execute corresponding airspace and frequency domain displacement add Close operation, then to encrypted matrix fritter M_outCalculate mapping value Map (M_out)；If Map (M_out) < δ, then by M_outIn picture Element is successively used as image A=(a to be encrypted_i,j)_m×nThe pixel of corresponding position, it is on the contrary by M_inMiddle pixel is directly as figure to be encrypted As A=(a_i,j)_m×nCorresponding position pixel；

Step 10: X is utilized₀,Y₀,Z₀To S_idCarry out rearrangement update；

Step 11: X is utilized₀,Y₀,Z₀To initial parameter μ₀And S_ms=< sm_i>₇₂In element be updated operation；

Step 12: if when k≤t, updating k=k+1, step 2~step 11 is executed repeatedly；

Step 13: by A=(a_i,j)_m×nOutput is used as encrypted image.

Further, step 2 is by S_msIt is mapped as S_h=< h₀,h₁,…,h₃₉> specific method be formula (1):

S_h=Draw (S_ms,start,gap,|S_h|) (1)

In formula (1), Draw () is that sequential element extracts function, and wherein start is to extract starting point, and gap is the sample skipped Number, | S_h| it is S_hMiddle number of elements, i.e., from S_msCirculation extracts | S_h| a 16 system number is as S_h, start, gap are respectively by formula (2) It is obtained with formula (3) mapping:

Step 3 is by S_hIt is divided intoTetrameric specific method is formula (4):

Step 3 willBe converted to 10 system decimal G in (0,1) range_i, i=0,1 ..., 3 it is specific Method is formula (5), and in formula (5), [] is round function:

Further, step 4 is by G₃As parameter alpha, G₀,G₁,G₂10 system decimal G being mapped as in (0,1) range₀′, G₁′,G₂' specific method be by G₀,G₁,G₂Respectively as the input parameter of formula (6), 3 sequences of formula (6) iteration 1 time generation are substituted into Train value G₀′,G₁′,G₂′；

Step 5 is by μ₀As system parameter, x_initThe random number in 5 (0,1) ranges is generated as sequence as initial value S_p=< p₀,p₁,p₂,p₃,p₄> specific method be by μ₀As system parameter, x_initFormula (7) are brought into iteration 5 times as initial value 5 random numbers generated are as sequence S_p=< p₀,p₁,p₂,p₃,p₄>

x_i+1=μ x_i(1-x_i) (7)；

By S in step 5_pConstruct the interval division sequence S ' in (0,1) range_p=< p '₀,p₁′,p′₂,p′₃,p′₄< tool Body method is by S_pMiddle element obtains interval division sequence S ' by descending order_p=< p '₀,p₁′,p′₂,p₃′,p′₄<。

Further, step 6 is by Y_init,μ₀It is mapped as μ₁The specific method of ∈ [3.57,4] is formula (8):

Step 6 is by X_initAnd μ₁The intermediate key ginseng in (0,1) range is generated respectively as initial value and system parameter iteration Number Z_initSpecific method be by X_initAnd μ₁Respectively as in formula (7) initial value and system parameter by formula (7) iteration 1 time work For intermediate key parameter Z_init；

x_i+1=μ x_i(1-x_i) (7)；

Step 7 is by X_init,Y_init,Z_initAs initial value, 3 random numbers of iteration 1 time generation are successively used as parameter X₀,Y₀, Z₀Specific method be by X_init,Y_init,Z_initAs the initial value of formula (9), 3 random numbers of iterative (9) 1 generations are successively As parameter X₀,Y₀,Z₀, formula (9) system parameter takes a=b=0.2, c=5.7；

Further, step 8 is by X₀,Y₀It is mapped as image A=(a to be encrypted_i,j)_m×nOn random point (r₀,v₀) specific side Method is formula (10), in formula (10)For downward rounding operation symbol；

Step 9 is by (r₀,v₀) it is used as starting point, from image A=(a to be encrypted_i,j)_m×nFilter out 4 × 4 matrix fritter M_in= (m_u,w)_4×4Specific method be formula (11):

Step 9 calculates M_inMapping value Map (M_in) specific method be by formula (12) calculate M_inVariance:

Step 9 is to encrypted matrix fritter M_outCalculate mapping value Map (M_out) specific method be same by formula (12) Method calculate M_outVariance；

By X in step 9₀,Y₀,Z₀Mapping value as transformation parameter v specific method be formula (13):

The specific method that corresponding airspace and frequency domain displacement cryptographic operation are executed in step 9 is formula (14):

M_out=Encrypt (M_in,v,P,f,S_id,S′_p) (14)

In formula (14), f={ f₀,f₁,…,f₅It is encrypted event set, S_idIt is the encrypted event subscript index sequence of f, S′_pFor interval division sequence, encrypted event set f corresponds to 6 group encryption events, wherein f₀,f₁,f₂Airspace displacement box encrypted event, As shown in formula (15), f₃,f₄,f₅Transform domain displacement box encrypted event, as shown in formula (16), f₀,f₁,…,f₅Corresponding displacement Box Px₀,Px₁,…,Px₅As shown in formula (17)；

In formula (15), M_codeIt is M_inNumber matrix, remember M_inIn element m_u,wIn M_codeIn number be id, then Permute₀The function that () function executes is by m_u,wIt is moved to Px_iMiddle element value is the coordinate position of (id+v) mod16；

In formula (16), M_HIt is Hadamard transform battle array, remembers M_tempIn element mt_u,wIn M_codeIn number be id and id ≠ ×, Permute₁The operation that () executes is by mt_u,wIt is moved to Px_iMiddle element value is the coordinate position of (id+v) mod16+1, together Permute₀The difference of () is Permute₁() in conversion process, M_tempIn (0,0) position element, i.e. id=× element It remains at (0,0) position and position change does not occur；

Further, step 10 utilizes X₀,Y₀,Z₀To S_idThe specific method for carrying out resetting update is by X₀,Y₀,Z₀By formula (18) It is mapped as start, gap with formula (19), right back-pushed-type (20) is to case index sequence S_idIt is updated:

S_id=Draw (S_id,start,gap,|S_id|) (20)；

X is utilized in step 11₀,Y₀,Z₀To initial parameter μ₀The specific method of update is formula (22):

To S in step 11_ms=< sm_i<₇₂In element be updated operation method particularly includes: first use X₀,Y₀,Z₀By formula (21) x is generated_init, then by x_init,μ₀Substitution formula (7) iteration generates random sequence S_R=< r_i>₇₂, by formula (23) to S_ms=< sm_i>₇₂In element be updated operation；

x_init=(X₀+X₀Y₀+X₀Y₀Z₀)mod1 (21)

x_i+1=μ x_i(1-x_i) (7)

The compound image selection decryption method of a kind of dynamic probability and null tone domain, comprising the following steps:

Step 1: key μ is inputted by user₀∈[3.57,4],S_MD5=< m₀,m₁,…,m₃₁>,S_SHA-1=< s₀,s₁,…,s₃₉ >, encrypt number t, t > 0 and encrypted image C=(c_i,j)_m×n, i=0,1 ..., m-1, j=0,1 ..., n-1, primary iteration control Parameter k=0, input encryption judgment threshold δ, δ > 0, by S_MD5And S_SHA-1Series connection is 16 system Number Sequence S_ms=S_MD5||S_SHA-1= <sm_i>₇₂, i=0,1 ..., 71 and initialization encryption event subscript index sequence S_id=<0,1 ..., 5>and intermediate key parameter sequence Arrange S_{X >},S_{Y >},S_{Z >},S_{X >},S_p′_>,S_{Id >}For empty sequence；

Step 2: by S_msIt is mapped as 16 system sequence S_h=< h₀,h₁,…,h₃₉>；

Step 3: by S_hIt is divided intoThen four parts willBe converted to (0,1) 10 system decimal G in range_i, i=0,1 ..., 3；

Step 4: by G₃As parameter alpha, G₀,G₁,G₂10 system decimal G being mapped as in (0,1) range₀′,G₁′,G₂', By G₀′,G₁′,G₂' it is used as key parameter X_init,Y_init,x_init, i.e. X_init=G₀′,Y_init=G₁′,x_init=G₂', by x_initMake For sequence S_{X >}In k-th of element

Step 5: by μ₀As system parameter, x_initThe random number in 5 (0,1) ranges is generated as sequence as initial value Arrange S_p=< p₀,p₁,p₂,p₃,p₄>, by S_pConstruct the interval division sequence S ' in (0,1) range_p=< p '₀,p₁′,p′₂,p′₃,p′₄ >, to obtain 6 probability intervals [0, p₀′),[p′₀,p₁′),[p₁′,p₂′),[p₂′,p₃′),[p₃′,p₄′),[p₄', 1], it will p₀′,p₁′,p₂′,p₃′,p₄' it is used as sequence S '_{P >}In 5k, 5k+1 ..., 5k+4 element

Step 6: by Y_init,μ₀The μ being mapped as in [3.57,4] range₁, by X_initAnd μ₁Respectively as initial value and system Parameter, then iteration 1 time mapping value is as intermediate key parameter Z_init；

Step 7: by X_init,Y_init,Z_init3 real value random numbers of chaos system iteration 1 time generation are substituted into as initial value X₀,Y₀,Z₀, and by X₀,Y₀,Z₀Successively respectively as S_{X >},S_{Y >},S_{Z >}In k-th of element

Step 8: X is utilized₀,Y₀,Z₀To S_idIt is updated, by S_idIn all elements be successively used as S_{Id >}In 6k, 6k+ 1 ..., 6k+5 element

Step 9: X is utilized₀,Y₀,Z₀To μ₀And S_ms=< sm_i>₇₂In element be updated operation；

Step 10: if k ≠ t updates k=k+1, step 2~step 9 is executed repeatedly, sequence can be obtained

Step 11: by S_{X >},S_{Y >}- 1 element of kthIt is mapped as C=(c_i,j)_m×nOn random point (r₀,v₀), By S_{Z >}- 1 element of kth in sequenceWithIt is mapped as transformation parameter v；

Step 12: by (r₀,v₀) it is used as starting point, from C=(c_i,j)_m×nFilter out 4 × 4 matrix fritter M_in=(m_u,w)_4×4, meter Calculate M_inMapping value Map (M_in), if Map (M_in) >=δ then updates k=k-1 as k ≠ 0, executes step 11, holds as k=0 Row step 14, if above-mentioned condition Map (M_in) >=δ is not satisfied, and takes S_{X >}- 1 element of kthAs probabilistic determination value P, utilize S′_{P >}5k-5,5k-4 ..., 5k-1 elementConstruct probability intervalTake S_{Id >}6k-6,6k-5 ..., 6k-1 elementAs S_id, using v as transformation parameter, the probability interval fallen into according to P, By matrix fritter M_in=(m_u,w)_4×4Decryption is matrix fritter M_out；

Step 13: M is calculated_outCorresponding mapping value Map (M_out), if Map (M_out) < δ, then by M_outIn element successively make For C=(c_i,j)_m×nThe pixel of corresponding position, it is on the contrary by M_inMiddle element is as C=(c_i,j)_m×nThe pixel of corresponding position, when k ≠ 0 Shi Gengxin k=k-1 executes step 11~step 13 repeatedly；

Step 14: by C=(c_i,j)_m×nOutput is used as decrypted image.

Further, by S in step 2_msIt is mapped as sequence S_h=< h₀,h₁,…,h₃₉< specific method be formula (1):

S_h=Draw (S_ms,start,gap,|S_h|) (1)

In formula (1), Draw () is that sequential element extracts function, and wherein start is to extract starting point, and gap is the sample skipped Number, | S_h| it is S_hMiddle number of elements, i.e., from S_msCirculation extracts | S_h| a 16 system number is as S_h, start, gap are respectively by formula (2) It is obtained with formula (3) mapping:

Step 3 is by S_hIt is divided intoTetrameric specific method is formula (4):

Step 3 willBe converted to 10 system decimal G in (0,1) range_i, i=0,1 ..., 3 it is specific Method is formula (5), and [] is round function:

Step 4 is by G₃As parameter alpha, G₀,G₁,G₂10 system decimal G being mapped as in (0,1) range₀′,G₁′,G₂' Specific method is by G₀,G₁,G₂Respectively as the input parameter of formula (6), 3 sequential value G of formula (6) iteration 1 time generation are substituted into₀′, G₁′,G₂′；

By μ in step 5₀As system parameter, x_initThe random number in 5 (0,1) ranges is generated as sequence as initial value Arrange S_p=< p₀,p₁,p₂,p₃,p₄> specific method be by μ₀As system parameter, x_initFormula (7) iteration 5 is brought into as initial value Secondary generation sequence S_p=< p₀,p₁,p₂,p₃,p₄>:

x_i+1=μ x_i(1-x_i) (7)；

By S in step 5_pConstruct the interval division sequence S ' in (0,1) range_p=p '₀,p₁′,p′₂,p′₃,p′₄> it is specific Method is by S_pMiddle element obtains interval division sequence S ' by descending order_p=< p '₀,p₁′,p′₂,p₃′,p′₄<。

Further, step 6 is by Y_init,μ₀The μ being mapped as in [3.57,4] range₁Specific method be formula (8):

Step 6 is by X_initAnd μ₁Respectively as initial value and system parameter iteration 1 time mapping value as intermediate key parameter Z_initSpecific method be use formula (7):

x_i+1=μ x_i(1-x_i) (7)；

Step 7 is by X_init,Y_init,Z_init3 real value random number X of chaos system iteration 1 time generation are substituted into as initial value₀, Y₀,Z₀Specific method be by X_init,Y_init,Z_initAs the initial value of formula (9), formula (9) system parameter takes a=b=0.2, c= 5.7,3 real value random value X of iterative (9) 1 generations₀,Y₀,Z₀:

Step 8 utilizes X₀,Y₀,Z₀To S_idThe specific method being updated is by X₀,Y₀,Z₀It is mapped by formula (18) and formula (19) For start, gap, right back-pushed-type (20) is to S_idIt is updated, whereinIt is accorded with for downward rounding operation:

S_id=Draw (S_id,start,gap,|S_id|) (20)；

Step 9 utilizes X₀,Y₀,Z₀To μ₀The specific method being updated is formula (22):

Step 9 is to S_ms=< sm_i<₇₂In element be updated operation method particularly includes: first use X₀,Y₀,Z₀By formula (21) Generate x_init, then by x_init,μ₀Substitution formula (7) iteration generates random sequence S_R=< r_i<₇₂, by formula (23) to S_ms=< sm_i<₇₂ In element be updated operation；

x_init=(X₀+X₀Y₀+X₀Y₀Z₀)mod1 (21)

x_i+1=μ x_i(1-x_i) (7)

Further, by S in step 11_{X >},S_{Y >}- 1 element of kthIt is mapped as C=(c_i,j)_m×nUpper random point (r₀,v₀) specific method be formula (24):

Step 11 is by S_{Z >}- 1 element of kth in sequenceWithIt is mapped as the specific method of transformation parameter v For formula (25):

Step 12 is by (r₀,v₀) it is used as starting point, from C=(c_i,j)_m×nFilter out 4 × 4 matrix fritter M_in=(m_u,w)_4×4's Specific method is formula (26):

Step 12 calculates M_inMapping value Map (M_in) specific method be by formula (12) to calculate M_inCorresponding variance:

By matrix M in step 12_in=(m_u,w)_4×4Decryption is matrix M_outSpecific method be formula (27):

M_out=Decryption (M_in,v,P,f′,S_id,S′_{P >}) (27)

In formula (27), f '={ f₀′,f₁′,…,f₅' it is program event set, f ' corresponds to 6 groups of program events, wherein f₀′, f₁′,f₂' airspace displacement box program event, as shown in formula (28), f₃′,f₄′,f₅' transform domain displacement box program event, such as formula (29) It is shown, f₀′,f₁′,…,f₅' corresponding displacement box Px₀,Px₁,…,Px₅As shown in formula (17):

In formula (28), M_codeIt is number matrix, remembers M_inIn element m_{U, w}In Px_iIn number be id, thenThe function that function executes is by m_u,wIt is moved to M_codeMiddle element number is the coordinate bit of (id-v+16) mod16 It sets；

In formula (29), M_HIt is Hadamard transform battle array, Permute₁ ^-1The operation that () executes is will be in Px_iIn number be id ≠ × element mt_u,wIt is moved to M_codeIt is middle number be (id-v+16) mod16+1 coordinate position, id=× element protect always It holds and position change does not occur in (0,0) position；

Step 13 calculates M_outCorresponding mapping value Map (M_out) specific method be to be calculated by the same method of formula (12) M_outCorresponding variance.

Compared with technology difference, advantages of the present invention is mainly reflected in:

1. The present invention gives a kind of, the selective image compound based on dynamic probability event and null tone domain is encrypted and is decrypted Method improves proposed Encryption Algorithm by introducing with the MD5 value of image plaintext attribute extreme sensitivity to be encrypted and SHA-1 value Plaintext sensibility, and pass through the compound crash-protective characteristics to improve single MD5 value or SHA-1 value to MD5 value and SHA-1 value, institute Method is proposed by the attribute of image to be encrypted, the probability interval fallen into, the encryption link of participation, corresponding transformation parameter is closely Be coupled in together, thus even if using identical key, to different plaintext images encrypted all by correspondence it is different plus Close result.

2. different with the encryption policy that tradition converts plaintext into random noise, designed encryption method only reduces image Visual quality, the approximation characteristic of image can be retained while encryption, and this approximation characteristic can be by preset Encryption threshold value is controlled, and is extracted so as to conveniently treat encrypted image for classifying and knowing another characteristic, while in decryption, Encrypted image can restore in high quality again.

3. traditional frequency domain selective cryptographic method may result in airspace pixel value when encrypting to frequency coefficient It overflows, to reduce the visual quality for recovering image.To reduce influence of the frequency coefficient change to visual quality of images is restored, Present invention adds encryption threshold value screening strategies, for being encrypted the screening of front and back threshold value to block of pixels selected at random, once Threshold value screening is more than preset threshold value before and after pixel block encryption, then abandons being encrypted to ensure that figure to block of pixels selected at random Visual quality when as restoring, while also the encryption visual quality of image randomized block is constrained.

4. what the present invention provided is not only a kind of image encryption method based on probability encryption event, and is that one kind has The image Probabilistic Encryption Methods of update mechanism.Mentioned method is the key parameter for giving user and image MD5, SHA- to be encrypted 1 value is mapped as different probability encryption sections, then by key parameter and MD5 value and SHA-1 value mapping parameters come to be added Close pixel carries out random screening, and different probability encryption events is executed according to the different probability section fallen into.Mentioned method is not Only probability interval is updated, and probability encryption arrangement of objects sequence and initial key are all carried out by mapping parameters It updates, then encryption random sequence is generated by updated initial key, the multiplexed sequence that MD5 value and SHA-1 value form is carried out Encryption updates, thus the sequence of encrypted event corresponding to different probability intervals also not exactly the same and different encrypted state phase Mutually tangle and close-coupled.

Detailed description of the invention

Fig. 1 is encryption flow figure；

Fig. 2 is decryption flow chart；

Fig. 3 is image to be encrypted, and MD5 value corresponding to 8 gray level images face, Fig. 3 for 256 × 256 resolution ratio is S_MD5=<D, 1,1, C, B, B, B, C, 3,7, A, A, 8, B, F, 5,1,4,5,1,3, C, E, F, F, 3,4, E, 4,2,0,7>, SHA-1 Value is S_SHA-1=< 2, A, E, 0, D, B, A, B, 1,1,6,3,2, E, 8,9, B, 4, A, D, D, 0,7,1, F, 9,3,7, C, 1,5,5,7, 0,E,C,2,A,1,E>；

Fig. 4 is embodiment: t=10000, encrypted image when δ=1300, the PSNR=22.939dB relative to Fig. 3；

Fig. 5 is embodiment: t=10000, decrypted image when δ=1300, the PSNR=50.825dB relative to Fig. 3；

Fig. 6 is embodiment: t=15000, encrypted image when δ=1600, the PSNR=21.752dB relative to Fig. 3；

Fig. 7 is embodiment: t=15000, decrypted image when δ=1600, relative to Fig. 3 PSNR=48.276dB；

Fig. 8 is embodiment: t=10000, and when δ=1300, the μ value for providing mistake corresponding (is revised as 3.989 3.989999998) decrypted image, the PSNR=21.282dB relative to Fig. 3；

Fig. 9 is embodiment: t=10000, when δ=1300, provides the S of mistake_MD5It is worth (S_MD5=< D, 1,1, C, B, B, B, C, 3,7, A, A, 8, B, F, 5, Isosorbide-5-Nitrae, 5,1,3, C, E, F, F, 3,4, E, 4,2,0,8 >) corresponding decrypted image, relative to Fig. 3's PSNR=21.278dB；

Figure 10 is embodiment: t=10000, when δ=1300, provides the S of mistake_SHA-1It is worth (S_SHA-1=< 2, A, E, 0, D, B, A, B, 1,1,6,3,2, E, 8,9, B, 4, A, D, D, 0,7,1, F, 9,3,7, C, 1,5,5,7,0, E, C, 2, A, 1, F >) corresponding solution Close image, the PSNR relative to Fig. 3 are PSNR=21.253dB；

Figure 11 is embodiment: t=10000, encrypted image when δ=2500, the PSNR=22.352dB relative to Fig. 3；

Figure 12 is embodiment: t=10000, decrypted image when δ=2500, the PSNR=43.642dB relative to Fig. 3；

Figure 13 is embodiment: t=10000, encrypted image when δ=3500, the PSNR=22.049dB relative to Fig. 3；

Figure 14 is embodiment: t=10000, decrypted image when δ=3500, the PSNR=46.990dB relative to Fig. 3；

Figure 15 is embodiment: t=15000, encrypted image when δ=2500, the PSNR=21.415dB relative to Fig. 3；

Figure 16 is embodiment: t=15000, decrypted image when δ=2500, the PSNR=39.739dB relative to Fig. 3；

Figure 17 is embodiment: t=15000, encrypted image when δ=3500, the PSNR=21.092dB relative to Fig. 3；

Figure 18 is embodiment: t=15000, decrypted image when δ=3500, the PSNR=37.506dB relative to Fig. 3.

Specific embodiment

Below in conjunction with specific embodiment, the present invention will be described:

Using JAVA jdk1.8.0_20 as case implementation environment, embodiment of the present invention is carried out specifically in conjunction with attached drawing It is bright, but it is not limited to the implementation case, wherein Fig. 1 is encryption flow figure, and Fig. 2 is decryption flow chart；

Ciphering process is as follows:

Step 1: choose image A as shown in figure 3, be 256 × 256 gray level image face, remember image A=to be encrypted (a_i,j)_m×n, i=0,1 ..., m-1, j=0,1 ..., the corresponding 40 16 system MD5 values of n-1 are S_MD5=< D, 1,1, C, B, B, B, C, 3,7, A, A, 8, B, F, 5,1,4,5,1,3, C, E, F, F, 3,4, E, 4,2,0,7 >, SHA-1 value is

S_SHA-1=< 2, A, E, 0, D, B, A, B, 1,1,6,3,2, E, 8,9, B, 4, A, D, D, 0,7,1, F, 9,3,7, C, 1,5, 5,7,0, E, C, 2, A, 1, E >, by S_MD5And S_SHA-1Series connection is 16 system Number Sequence S_ms=S_MD5||S_SHA-1=< sm_i>₇₂, i=0, 1 ..., 71 and initialization encryption event subscript index sequence S_idFor S_id=<0,1 ..., 5>, setting encryption number t=10000, Primary iteration control parameter k=1 selectes initial parameter μ₀=3.989, encrypt judgment threshold δ=1300；

Step 2: by S_msSubstitution formula (1) is mapped as 16 system sequence S_h=< h₀,h₁,…,h₃₉>, by S_msFormula is substituted into respectively (2) and formula (3) is mapped as start, gap；Such as: by S_ms=< D, 1,1, C, B, B, B, C, 3,7, A, A, 8, B, F, 5,1,4,5, 1,3, C, E, F, F, 3,4, E, 4,2,0,7,2, A, E, 0, D, B, A, B, 1,1,6,3,2, E, 8,9, B, 4, A, D, D, 0,7,1, F, 9,3,7, C, 1,5,5,7,0, E, C, 2, A, 1, E > substitution formula (1) are mapped as S_h=< A, E, 7,2,4,0, A, B, 6,9,0, C, 2, B, 5,4, B, 5, C, F, D, D, C, 1,7,3,1,1, B, 4,1,0,2,1, B, E, 3,7, D, 9 >, by S_msFormula (2) and formula are substituted into respectively (3) start=43, gap=67 can be obtained；

Step 3: by S_hIt is divided by formula (4)Then four parts willIt substitutes into Formula (5) is converted to 10 system decimal G in (0,1) range_i, i=0,1 ..., 3；Such as: it can be by S_hIt is divided into Substitution formula (5) mapping are as follows: G₀=0.6748477158235295, G₁= 0.07244421382352942,G₂=0.8483371302352942, G₃=0.06013199052941176；

Step 4: by G₃As parameter alpha, G₀,G₁,G₂Respectively as the input parameter of formula (6), formula (6) are substituted into iteration 1 time Generate 3 sequential value G₀′,G₁′,G₂', by G₀′,G₁′,G₂' it is used as key parameter X_init,Y_init,x_init；

Such as: α=0.06013199052941176 is taken, by G₀,G₁,G₂Formula (6) are substituted into respectively maps G₀'= 0.34595526276037764,G₁'=0.9869000506772724, G₂'=0.16136613677290165, X_init= 0.34595526276037764,Y_init=0.9869000506772724, x_init=0.16136613677290165；

Step 5: by μ₀As system parameter, x_init5 random numbers for bringing formula (7) iteration 5 times generations into as initial value are made For sequence S_p=< p₀,p₁,p₂,p₃,p₄>, by S_pMiddle element obtains interval division sequence S ' by descending order_p=< p '₀, p₁′,p′₂,p₃′,p′₄>；Such as: μ₀=3.989, x_init=0.16136613677290165 substitutes into formula (7) iteration 5 times mappings, S_p=< p₀,p₁,p₂,p₃,p₄>,p₀=0.5398198285301286, p₁=0.9909249668295106, p₂= 0.035871788327397826,p₃=0.13795957748394325, p₄=0.4743987358004721, then it can obtain S '_p =< p '₀,p₁′,p′₂,p′₃,p′₄<, i.e. p₀'=0.035871788327397826, p₁'=0.13795957748394325, p₂′ =0.4743987358004721, p₃'=0.5398198285301286, p₄'=0.9909249668295106；

Step 6: by Y_init,μ₀Substitution formula (8) is mapped as μ₁∈ [3.57,4], by X_initAnd μ₁It is initial respectively as formula (7) Value and system parameter press formula (7) iteration 1 time as intermediate key parameter Z_init；Such as: by μ₀=3.989, Y_init= 0.9869000506772724, which substitutes into formula (8), can obtain μ₁=3.9916826088662414, by X_init= 0.34595526276037764 and μ₁=3.9916826088662414, which substitute into formula (7), can obtain Z_init= 0.9031988978023509；

Step 7: by X_init,Y_init,Z_initAs the initial value of formula (9), 3 real value random numbers of iterative (9) 1 generations Successively it is used as parameter X₀,Y₀,Z₀, formula (9) system parameter takes a=b=0.2, c=5.7；

Such as: X_init=0.34595526276037764, Y_init=0.9869000506772724, Z_init= 0.9031988978023509 obtains X by formula (9)₀=0.1755933912994469, Y₀=1.0326377639685018, Z₀= 0.5476634933830886；

Step 8: by X₀,Y₀It is A=(a that substitution formula (10), which is mapped as image to be encrypted,_i,j)_m×nOn random point (r₀,v₀)；

Such as: X₀=0.1755933912994469, Y₀=1.0326377639685018 substitute into formula (10), can be mapped as Encrypted image is A=(a_i,j)_m×nOn random point r₀=36, v₀=6；

Step 9: by (r₀,v₀) it is used as starting point, by formula (11) from image A=(a to be encrypted_i,j)_m×nFilter out M_in= (m_u,w)_4×4, by M_inSubstitution formula (12) calculates mapping value Map (M_in), if Map (M_in) >=δ then executes step 10, on the contrary by x_init As probabilistic determination value P, by X₀,Y₀,Z₀Substitution formula (13) mapping transformation parameter v, according to the P probability interval fallen into and S_id, press Formula (14) executes corresponding airspace and frequency domain displacement cryptographic operation, and the same method of right back-pushed-type (12) calculates M_outMapping value Map (M_out), if Map (M_out) < δ, then by M_outIn pixel be successively used as image A=(a to be encrypted_i,j)_m×nThe pixel of corresponding position, Otherwise by M_inMiddle pixel is directly as image A=(a to be encrypted_i,j)_m×nThe pixel of corresponding position；Such as: by (r₀,v₀) be used as Point, by formula (11) from image A=(a to be encrypted_i,j)_m×nFilter out 4 × 4 matrix fritterBy M_inSubstitution formula (12), due to Map (M_in)=172.4375 are Map (M_in) < δ passes through Judgement continues to execute cryptographic operation, and P=0.16136613677290165 passes through X₀=0.1755933912994469, Y₀= 1.0326377639685018,Z₀=0.5476634933830886 substitutes into formula (13) mapping transformation parameter v=10, according to P institute The probability interval and S fallen into_id, corresponding airspace is executed by formula (14) and frequency domain displacement cryptographic operation obtainsBy M_outSubstitution formula (12) judged, Map (M_out)=172.4375 are Map (M_out) < δ, then by M_outMiddle element is successively used as image A=(a to be encrypted_i,_j)_m×nCorresponding position pixel；

Step 10: X is utilized₀,Y₀,Z₀It is mapped as start, gap by formula (18) and formula (19), right back-pushed-type (20) is to S_idInto Row updates；Such as: by S_id=0,1,2 ..., and 5 } substitute into the new S of formula (20) mapping_id={ 3,1,0,2,5,4 }, by X₀= 0.1755933912994469,Y₀=1.0326377639685018, Z₀=0.5476634933830886 substitutes into formula respectively (18), (19) can obtain parameter start=0, gap=3；

Step 11: X is utilized₀,Y₀,Z₀Substitution formula (22) maps initial parameter μ₀, then use X₀,Y₀,Z₀It is generated by formula (21) x_init, then by x_init,μ₀Substitution formula (7) iteration generates random sequence S_R=< r_i>₇₂, by formula (23) to S_ms=< sm_i>₇₂In Element is updated operation；Such as: by X₀,Y₀,Z₀Substitution formula (22) undated parameter μ₀=3.7798190064841766, by X₀, Y₀,Z₀Substitution formula (21) maps x_init=0.45622249450285557, by x_init,μ₀Substitution formula (7) maps random sequence S_R= <r_i>₇₂, and by S_R=< r_i>₇₂To S_ms=< sm_i>₇₂Encryption, which updates, obtains new S_ms=< D, 5,9,2, F, 8, E, 1, D, 1,6, F, E,D,F,D,C,7,F,B,5,6,9,3,C,C,0,D,1,8,0,9,B,D,9,0,F,1,9,8,0,2,A,B,1,9,9,A,F,7, 0,A,E,C,C,B,9,D,E,9,1,8,1,6,E,6,3,5,D,3,E,E>；

Step 12: if when k≤t, updating k=k+1, step 2~step 11 is executed repeatedly；

Step 13: by A=(a_i,j)_m×nOutput is as shown in Figure 4 as encrypted image.

Decrypting process is as follows:

Step 1: input key μ₀=3.989, encryption number t=10000, juxtaposition k=0, input encryption judgment threshold δ= 1300, S_MD5=<D, 1,1, C, B, B, B, C, 3,7, A, A, 8, B, F, 5, Isosorbide-5-Nitrae, 5,1,3, C, E, F, F, 3,4, E, 4,2,0,7>, S_SHA-1=< 2, A, E, 0, D, B, A, B, 1,1,6,3,2, E, 8,9, B, 4, A, D, D, 0,7,1, F, 9,3,7, C, 1,5,5,7,0, E, C, 2, A, 1, E >, by S_MD5And S_SHA-1Series connection is 16 system Number Sequence S_ms=S_MD5||S_SHA-1=< sm_i>₇₂, i=0,1 ..., 71 simultaneously Initialization encryption event subscript index sequence S_id=<0,1 ..., 5>and intermediate key argument sequence S_{X >},S_{Y >},S_{Z >},S_{X >},S_p ′_>,S_{Id >}For empty sequence, encrypted image C=(c_i,j)_m×n, i=0,1 ..., m-1, j=0,1 ..., n-1 is as shown in Figure 4；

Step 2: by S_msSubstitution formula (1) is mapped as 16 system sequence S_h=< h₀,h₁,…,h₃₉>, by S_msFormula is substituted into respectively (2) and formula (3) maps start, gap；Such as: by S_ms=< D, 1,1, C, B, B, B, C, 3,7, A, A, 8, B, F, 5,1,4,5,1, 3, C, E, F, F, 3,4, E, 4,2,0,7,2, A, E, 0, D, B, A, B, 1,1,6,3,2, E, 8,9, B, 4, A, D, D, 0,7,1, F, 9, 3,7, C, 1,5,5,7,0, E, C, 2, A, 1, E > substitute into formula (1) mapping S_h=< A, E, 7,2,4,0, A, B, 6,9,0, C, 2, B, 5, 4, B, 5, C, F, D, D, C, 1,7,3,1,1, B, 4,1,0,2,1, B, E, 3,7, D, 9 >, wherein by S_msFormula (2) and formula are substituted into respectively (3) start=43, gap=67 are mapped；

Step 3: by S_hIt is divided by formula (4)Then four parts willIt substitutes into Formula (5) is converted to 10 system decimal G in (0,1) range_i, i=0,1 ..., 3；Such as: by S_hIt is divided into Substitution formula (5) is mapped as G₀=0.6748477158235295, G₁= 0.07244421382352942,G₂=0.8483371302352942, G₃=0.06013199052941176；

Step 4: by G₃As parameter alpha, G₀,G₁,G₂Respectively as the input parameter of formula (6), formula (6) are substituted into iteration 1 time Generate 3 sequential value G₀′,G₁′,G₂', by G₀′,G₁′,G₂' it is used as key parameter X_init,Y_init,x_init, by x_initAs sequence S_{X >}In k-th of elementSuch as: α=0.06013199052941176 is used as initial parameter, by G₀,G₁,G₂It substitutes into respectively Formula (6) is mapped as G₀'=0.34595526276037764, G₁'=0.9869000506772724, G₂'= 0.16136613677290165 i.e. X_init=0.34595526276037764, Y_init=0.9869000506772724, x_init= 0.16136613677290165, by x_initAs sequence S_{X >}In k-th of element

Step 5: by μ₀As system parameter, x_init5 random numbers for bringing formula (7) iteration 5 times generations into as initial value are made For sequence S_p=< p₀,p₁,p₂,p₃,p₄>, by S_pMiddle element obtains interval division sequence S ' by descending order_p=< p '₀, p₁′,p′₂,p₃′,p′₄>, by p₀′,p₁′,p₂′,p₃′,p₄' it is used as sequence S '_p5k in >, 5k+1 ..., 5k+4 elementSuch as: μ₀=3.989, x_init=0.16136613677290165 substitutes into formula (7) iteration 5 times mappings S_p=< p₀,p₁,p₂,p₃,p₄>,p₀=0.5398198285301286, p₁=0.9909249668295106, p₂= 0.035871788327397826,p₃=0.13795957748394325, p₄=0.4743987358004721, then it can be obtained S′_p=< p '₀,p₁′,p′₂,p′₃,p′₄>, i.e. p₀'=0.035871788327397826, p₁'=0.13795957748394325, p₂'=0.4743987358004721, p₃'=0.5398198285301286, p₄'=0.9909249668295106, by p₀′, p₁′,p₂′,p₃′,p₄' it is used as sequence S '_{P >}In 5k, 5k+1 ..., 5k+4 element

Step 6: by Y_init,μ₀Substitution formula (8) is mapped as μ₁∈ [3.57,4], by X_initAnd μ₁Respectively as in formula (7) Initial value and system parameter press formula (7) iteration 1 time as intermediate key parameter Z_init；Such as: μ₀=3.989, Y_init= 0.9869000506772724, which substitutes into formula (8), maps μ₁=3.9916826088662414, by X_init= 0.34595526276037764,μ₁=3.9916826088662414, which substitute into formula (7), to obtain: Z_init= 0.9031988978023509；

Step 7: by X_init,Y_init,Z_initAs the initial value of formula (9), 3 real value random numbers of iterative (9) 1 generations Successively it is used as parameter X₀,Y₀,Z₀, formula (9) system parameter takes a=b=0.2, c=5.7, and by X₀,Y₀,Z₀Successively respectively as S_{X >},S_{Y >},S_{Z >}In k-th of elementSuch as: X_init=0.34595526276037764, Y_init= 0.9869000506772724, Z_init=0.9031988978023509 substitutes into 1 mapping X of formula (9) iteration₀= 0.1755933912994469,Y₀=1.0326377639685018, Z₀=0.5476634933830886, by X₀,Y₀,Z₀Successively Respectively as S_{X >},S_{Y >},S_{Z >}In k-th of element

Step 8: X is utilized₀,Y₀,Z₀It is mapped as start, gap by formula (18) and formula (19), right back-pushed-type (20) is to S_idIt carries out It updates, by S_idIn all elements be successively used as S_{Id >}In 6k, 6k+1 ..., 6k+5 elementSuch as: by S_id=0,1,2 ..., and 5 } substitute into the new S of formula (20) mapping_id=3,1,0,2, 5,4 }, wherein by X₀=0.1755933912994469, Y₀=1.0326377639685018, Z₀= 0.5476634933830886 substitutes into formula (18) respectively, (19) mapping parameters start=0, gap=3, by S_idIn all elements Successively it is used as S_{Id >}In 6k, 6k+1 ..., 6k+5 element

Step 9: X is utilized₀,Y₀,Z₀Substitution formula (22) maps μ₀, then use X₀,Y₀,Z₀X is generated by formula (21)_init, then will x_init,μ₀Substitution formula (7) iteration generates random sequence S_R=< r_i>₇₂, by formula (23) to S_ms=< ms_i>₇₂In element be updated Operation；Such as: by X₀,Y₀,Z₀Substitution formula (22) undated parameter μ₀=3.7798190064841766, by X₀,Y₀,Z₀Substitution formula (21) x is mapped_init=0.45622249450285557, by x_init, the substitution of μ 0 formula (7) mapping random sequence S_R=< r_i>₇₂, and will S_R=< r_i>₇₂To S_ms=< sm_i>₇₂Encryption, which updates, obtains new S_ms=< D, 5,9,2, F, 8, E, 1, D, 1,6, F, E, D, F, D, C, 7,F,B,5,6,9,3,C,C,0,D,1,8,0,9,B,D,9,0,F,1,9,8,0,2,A,B,1,9,9,A,F,7,0,A,E,C,C, B,9,D,E,9,1,8,1,6,E,6,3,5,D,3,E,E>；

Step 10: if k ≠ t updates k=k+1, step 2~step 9 is executed repeatedly, sequence can be obtained

Step 11: by S_{X >},S_{Y >}- 1 element of kthSubstitution formula (24) is mapped as C=(c_i,j)_m×nOn it is random Point (r₀,v₀), by S_{Z >}- 1 element of kth in sequenceWithFormula (25) are substituted into together is mapped as transformation parameter v；Such as:Substitution formula (24) maps C= (c_i,j)_m×nOn random point r₀=238, v₀=52, it willWithSubstitution formula (25) v=1 is mapped；

Step 12: by (r₀,v₀) it is used as starting point, by formula (26) from C=(c_i,j)_m×nFilter out 4 × 4 matrix fritter M_in= (m_u,w)_4×4, M is calculated by formula (12)_inMapping value Map (M_in), if Map (M_in) >=δ then updates k=k-1 as k ≠ 0, executes Step 11 executes step 14 as k=0, if above-mentioned condition Map (M_in) >=δ is not satisfied, and takes S_{X >}- 1 element of kthMake For probabilistic determination value P, S ' is utilized_{P >}5k-5,5k-4 ..., 5k-1 elementConstruct probability intervalTake S_{Id >}6k-6,6k-5 ..., 6k-1 member ElementAs S_id, using v as transformation parameter, the probability interval fallen into according to P, by formula (27) By matrix fritter M_in=(m_u,w)_4×4Decryption is matrix fritter M_out；Such as: by (r₀,v₀) it is used as starting point, by formula (26) from C= (c_i,j)_m×nFilter out 4 × 4 matrix fritterBy M_inSubstitution formula (12) judged, Due to Map (M_in)=239.75 are Map (M_in) < δ, then by S_{X >}- 1 element of kthAs probabilistic determination value P= 0.31040996788505415, utilize S '_{P >}5k-5,5k-4 ..., 5k-1 element Construct probability intervalTake S_{Id >}6k-6,6k-5 ..., 6k-1 member ElementSequence is indexed as subscript Column, using v=1 as transformation parameter, the probability interval fallen into according to P, by matrix fritter M_in=(m_u,w)_4×4Substitution formula (27) solution Close is matrix fritter

Step 13: M is calculated by formula (12) same method_outCorresponding mapping value Map (M_out), if Map (M_out) < δ, then By M_outIn element be successively used as C=(c_i,j)_m×nThe pixel of corresponding position, it is on the contrary by M_inMiddle element is as C=(c_i,j)_m×nIt is right The pixel for answering position updates k=k-1 as k ≠ 0, executes step 11~step 13 repeatedly；Such as: by M_outSubstitution formula (12), Due to Map (M_out)=237.484375 are Map (M_out) < δ, then by M_outMiddle pixel is successively used as C=(c_i,j)_m×nCorresponding position Pixel；

Step 14: by C=(c_i,j)_m×nOutput is as shown in Figure 5 as decrypted image.

Fig. 6 is that encryption number is respectively t=15000, and the encrypted image of δ=1600, Fig. 7 is corresponding decrypted image, can from Fig. 6 Find out the method for the present invention encrypted image relative to original image although can recognize, visual quality is integrally poor, solves as can be seen from Figure 7 Close image is clear relative to original image visual quality, has certain application value；

Fig. 8~10 are respectively to modify one of them corresponding decrypted image；It can be seen that the method for the present invention from decrypted image, it is right The key and picture characteristics extreme sensitivity to be encrypted that user provides will lead to decrypted image vision matter if providing the parameter of mistake Amount decline, decrypted image visual quality are more fuzzy；

Figure 11,13,15,17 encrypted image embodiments corresponding when being different encryption number t, δ respectively, Figure 12,14, 16,18 be corresponding decrypted image embodiment, be can be seen that from decrypted image visual quality, by controlling t, δ, be can be obtained The decrypted image of different visual qualities, to have more extensive application value.

Claims (10)

1. the compound image selection encryption method of a kind of dynamic probability and null tone domain, it is characterised in that the following steps are included:

Step 1: remember that image to be encrypted is A=(a_i,j)_m×nAnd a_i,j∈ 0,1 ..., 255 }, i=0,1 ..., m-1, j=0, 1 ..., n-1, setting encryption number t, t > 0, primary iteration control parameter k=1, select initial parameter μ₀∈ [3.57,4] and Setting encryption judgment threshold δ, δ > 0, remember the MD5 value of A and SHA-1 value are respectively 16 system Number Sequence S_MD5=< m₀,m₁,…,m₃₁ > and S_SHA-1=< s₀,s₁,…,s₃₉>, by S_MD5And S_SHA-1Series connection is 16 system Number Sequence S_ms=S_MD5||S_SHA-1=< sm_i>₇₂,i =0,1 ..., 71 and initialization encryption event subscript index sequence S_idFor S_id=<0,1 ..., 5>, wherein " | | " it is bit bit string Serial operation symbol；

Step 2: by S_msIt is mapped as 16 system sequence S_h=< h₀,h₁,…,h₃₉>；

Step 3: by S_hIt is divided intoThen four parts willBe converted to (0,1) range 10 interior system decimal G_i, i=0,1 ..., 3；

Step 4: by G₃As parameter alpha, G₀,G₁,G₂10 system decimal G ' being mapped as in (0,1) range₀,G′₁,G′₂, by G ′₀,G′₁,G′₂As key parameter X_init,Y_init,x_init, i.e. X_init=G '₀,Y_init=G '₁,x_init=G '₂；

Step 5: by initial parameter μ₀As system parameter, key parameter x_initIt is generated in 5 (0,1) ranges as initial value Random number is as sequence S_p=< p₀,p₁,p₂,p₃,p₄>, by S_pConstruct the interval division sequence S ' in (0,1) range_p=< p '₀, p′₁,p′₂,p′₃,p′₄>, to obtain probability interval [0, p '₀),[p′₀,p′₁),[p′₁,p′₂),[p′₂,p′₃),[p′₃,p′₄), [p′₄,1]；

Step 6: by key parameter Y_init,μ₀It is mapped as μ₁∈ [3.57,4], by X_initAnd μ₁Join respectively as initial value and system Number iteration generates the intermediate key parameter Z in (0,1) range_init；

Step 7: by X_init,Y_init,Z_initAs initial value, 3 real value random numbers of iteration 1 time generation are successively used as parameter X₀,Y₀, Z₀；

Step 8: by X₀,Y₀It is mapped as image A=(a to be encrypted_i,j)_m×nOn random point (r₀,v₀)；

Step 9: by (r₀,v₀) it is used as starting point, from image A=(a to be encrypted_i,j)_m×nFilter out M_in=(m_u,w)_4×4, calculate M_in's Mapping value Map (M_in), if Map (M_in) >=δ then executes step 10, on the contrary by x_initAs probabilistic determination value P, by X₀,Y₀,Z₀'s Mapping value is as transformation parameter v, according to the P probability interval fallen into and S_id, execute corresponding airspace and frequency domain displacement encryption behaviour Make, then to encrypted matrix fritter M_outCalculate mapping value Map (M_out)；If Map (M_out) < δ, then by M_outIn pixel according to It is secondary to be used as image A=(a to be encrypted_i,j)_m×nThe pixel of corresponding position, it is on the contrary by M_inMiddle pixel is directly as image A=to be encrypted (a_i,j)_m×nCorresponding position pixel；

Step 10: X is utilized₀,Y₀,Z₀To S_idCarry out rearrangement update；

Step 11: X is utilized₀,Y₀,Z₀To initial parameter μ₀And S_ms=< sm_i>₇₂In element be updated operation；

Step 12: if when k≤t, updating k=k+1, step 2~step 11 is executed repeatedly；

Step 13: by A=(a_i,j)_m×nOutput is used as encrypted image.

2. the compound image selection encryption method of a kind of dynamic probability as described in claim 1 and null tone domain, feature exist In: step 2 by S_msIt is mapped as S_h=< h₀,h₁,…,h₃₉> specific method be formula (1):

S_h=Draw (S_ms,start,gap,|S_h|) (1)

In formula (1), Draw () is that sequential element extracts function, and wherein start is to extract starting point, and gap is the sample number skipped, | S_h| it is S_hMiddle number of elements, i.e., from S_msCirculation extracts | S_h| a 16 system number is as S_h, start, gap are respectively by formula (2) and formula (3) mapping obtains:

Step 3 is by S_hIt is divided intoTetrameric specific method is formula (4):

Step 3 willBe converted to 10 system decimal G in (0,1) range_i, i=0,1 ..., 3 specific method For formula (5), in formula (5), [] is round function:

3. the compound image selection encryption method of a kind of dynamic probability as described in claim 1 and null tone domain, feature exist In: step 4 by G₃As parameter alpha, G₀,G₁,G₂10 system decimal G ' being mapped as in (0,1) range₀,G′₁,G′₂It is specific Method is by G₀,G₁,G₂Respectively as the input parameter of formula (6), 3 sequential value G ' of formula (6) iteration 1 time generation are substituted into₀,G′₁, G′₂；

Step 5 is by μ₀As system parameter, x_initThe random number in 5 (0,1) ranges is generated as sequence S as initial value_p= <p₀,p₁,p₂,p₃,p₄> specific method be by μ₀As system parameter, x_initFormula (7) iteration 5 times generations are brought into as initial value 5 random numbers as sequence S_p=< p₀,p₁,p₂,p₃,p₄>

x_i+1=μ x_i(1-x_i) (7)；

By S in step 5_pConstruct the interval division sequence S ' in (0,1) range_p=< p '₀,p′₁,p′₂,p′₃,p′₄> specific method For by S_pMiddle element obtains interval division sequence S ' by descending order_p=< p '₀,p′₁,p′₂,p′₃,p′₄>。

4. the compound image selection encryption method of a kind of dynamic probability as described in claim 1 and null tone domain, feature exist In: step 6 by Y_init,μ₀It is mapped as μ₁The specific method of ∈ [3.57,4] is formula (8):

Step 6 is by X_initAnd μ₁The intermediate key parameter in (0,1) range is generated respectively as initial value and system parameter iteration Z_initSpecific method be by X_initAnd μ₁Respectively as in formula (7) initial value and system parameter press 1 conduct of formula (7) iteration Intermediate key parameter Z_init；

x_i+1=μ x_i(1-x_i) (7)；

Step 7 is by X_init,Y_init,Z_initAs initial value, 3 random numbers of iteration 1 time generation are successively used as parameter X₀,Y₀,Z₀'s Specific method is by X_init,Y_init,Z_initAs the initial value of formula (9), 3 random number successively conducts of iterative (9) 1 generations Parameter X₀,Y₀,Z₀, formula (9) system parameter takes a=b=0.2, c=5.7；

5. the compound image selection encryption method of a kind of dynamic probability as described in claim 1 and null tone domain, feature exist In: step 8 by X₀,Y₀It is mapped as image A=(a to be encrypted_i,j)_m×nOn random point (r₀,v₀) specific method be formula (10), In formula (10)For downward rounding operation symbol；

Step 9 is by (r₀,v₀) it is used as starting point, from image A=(a to be encrypted_i,j)_m×nFilter out 4 × 4 matrix fritter M_in= (m_u,w)_4×4Specific method be formula (11):

Step 9 calculates M_inMapping value Map (M_in) specific method be by formula (12) calculate M_inVariance:

Step 9 is to encrypted matrix fritter M_outCalculate mapping value Map (M_out) specific method be by the same side of formula (12) Method calculates M_outVariance；

By X in step 9₀,Y₀,Z₀Mapping value as transformation parameter v specific method be formula (13):

The specific method that corresponding airspace and frequency domain displacement cryptographic operation are executed in step 9 is formula (14):

M_out=Encrypt (M_in,v,P,f,S_id,S′_p) (14)

In formula (14), f={ f₀,f₁,…,f₅It is encrypted event set, S_idIt is the encrypted event subscript index sequence of f, S '_pFor Interval division sequence, encrypted event set f correspond to 6 group encryption events, wherein f₀,f₁,f₂Airspace displacement box encrypted event, such as formula (15) shown in, f₃,f₄,f₅Transform domain displacement box encrypted event, as shown in formula (16), f₀,f₁,…,f₅Corresponding displacement box Px₀,Px₁,…,Px₅As shown in formula (17)；

In formula (15), M_codeIt is M_inNumber matrix, remember M_inIn element m_u,wIn M_codeIn number be id, then Permute₀ The function that () function executes is by m_u,wIt is moved to Px_iMiddle element value is the coordinate position of (id+v) mod16；

In formula (16), M_HIt is Hadamard transform battle array, remembers M_tempIn element mt_u,wIn M_codeIn number be id and id ≠ ×, Permute₁The operation that () executes is by mt_u,wIt is moved to Px_iMiddle element value is the coordinate position of (id+v) mod16+1, together Permute₀The difference of () is Permute₁() in conversion process, M_tempIn (0,0) position element, i.e. id=× element It remains at (0,0) position and position change does not occur；

6. the compound image selection encryption method of a kind of dynamic probability as described in claim 1 and null tone domain, feature exist In: step 10 utilizes X₀,Y₀,Z₀To S_idThe specific method for carrying out resetting update is by X₀,Y₀,Z₀It is mapped by formula (18) and formula (19) For start, gap, right back-pushed-type (20) is to case index sequence S_idIt is updated:

S_id=Draw (S_id,start,gap,|S_id|) (20)；

X is utilized in step 11₀,Y₀,Z₀To initial parameter μ₀The specific method of update is formula (22):

To S in step 11_ms=< sm_i>₇₂In element be updated operation method particularly includes: first use X₀,Y₀,Z₀By formula (21) Generate x_init, then by x_init,μ₀Substitution formula (7) iteration generates random sequence S_R=< r_i>₇₂, by formula (23) to S_ms=< sm_i>₇₂ In element be updated operation；

x_init=(X₀+X₀Y₀+X₀Y₀Z₀)mod1 (21)

x_i+1=μ x_i(1-x_i) (7)

7. the compound image selection decryption method of a kind of dynamic probability corresponding with claim 1 and null tone domain, feature Be the following steps are included:

Step 1: key μ is inputted by user₀∈[3.57,4],S_MD5=< m₀,m₁,…,m₃₁>,S_SHA-1=< s₀,s₁,…,s₃₉>, add Close number t, t > 0 and encrypted image C=(c_i,j)_m×n, i=0,1 ..., m-1, j=0,1 ..., n-1, primary iteration control parameter K=0, input encryption judgment threshold δ, δ > 0, by S_MD5And S_SHA-1Series connection is 16 system Number Sequence S_ms=S_MD5||S_SHA-1=< sm_i >₇₂, i=0,1 ..., 71 and initialization encryption event subscript index sequence S_id=<0,1 ..., 5>and intermediate key argument sequence S_{X >},S_{Y >},S_{Z >},S_{X >},S′_{P >},S_{Id >}For empty sequence；

Step 2: by S_msIt is mapped as 16 system sequence S_h=< h₀,h₁,…,h₃₉>；

Step 3: by S_hIt is divided intoThen four parts willBe converted to (0,1) range 10 interior system decimal G_i, i=0,1 ..., 3；

Step 4: by G₃As parameter alpha, G₀,G₁,G₂10 system decimal G being mapped as in (0,1) range₀′,G₁′,G₂', it will G₀′,G₁′,G₂' it is used as key parameter X_init,Y_init,x_init, i.e. X_init=G₀′,Y_init=G₁′,x_init=G₂', by x_initAs Sequence S_{X >}In k-th of element

Step 5: by μ₀As system parameter, x_initThe random number in 5 (0,1) ranges is generated as sequence S as initial value_p =< p₀,p₁,p₂,p₃,p₄>, by S_pConstruct the interval division sequence S ' in (0,1) range_p=< p '₀,p′₁,p′₂,p′₃,p′₄>, from And obtain 6 probability intervals [0, p '₀),[p′₀,p′₁),[p′₁,p′₂),[p′₂,p′₃),[p′₃,p′₄),[p′₄, 1], by p '₀, p′₁,p′₂,p′₃,p′₄As sequence S '_{P >}In 5k, 5k+1 ..., 5k+4 element

Step 6: by Y_init,μ₀The μ being mapped as in [3.57,4] range₁, by X_initAnd μ₁Respectively as initial value and system parameter The mapping value that iteration is 1 time is as intermediate key parameter Z_init；

Step 7: by X_init,Y_init,Z_init3 real value random number X of chaos system iteration 1 time generation are substituted into as initial value₀,Y₀, Z₀, and by X₀,Y₀,Z₀Successively respectively as S_{X >},S_{Y >},S_{Z >}In k-th of element

Step 8: X is utilized₀,Y₀,Z₀To S_idIt is updated, by S_idIn all elements be successively used as S_{Id >}In 6k, 6k+1 ..., 6k+5 element

Step 9: X is utilized₀,Y₀,Z₀To μ₀And S_ms=< sm_i>₇₂In element be updated operation；

Step 10: if k ≠ t updates k=k+1, step 2~step 9 is executed repeatedly, sequence can be obtained

Step 11: by S_{X >},S_{Y >}- 1 element of kthIt is mapped as C=(c_i,j)_m×nOn random point (r₀,v₀), by S_{Z >} - 1 element of kth in sequenceWithIt is mapped as transformation parameter v；

Step 12: by (r₀,v₀) it is used as starting point, from C=(c_i,j)_m×nFilter out 4 × 4 matrix fritter M_in=(m_u,w)_4×4, calculate M_in Mapping value Map (M_in), if Map (M_in) >=δ, then update k=k-1 as k ≠ 0, executes step 11, and the is executed as k=0 14 steps, if above-mentioned condition Map (M_in) >=δ is not satisfied, and takes S_{X >}- 1 element of kthAs probabilistic determination value P, S ' is utilized_{P >} 5k-5,5k-4 ..., 5k-1 elementConstruct probability intervalTake S_{Id >}6k-6,6k-5 ..., 6k-1 elementAs S_id, using v as transformation parameter, the probability interval fallen into according to P, By matrix fritter M_in=(m_u,w)_4×4Decryption is matrix fritter M_out；

Step 13: M is calculated_outCorresponding mapping value Map (M_out), if Map (M_out) < δ, then by M_outIn element be successively used as C =(c_i,j)_m×nThe pixel of corresponding position, it is on the contrary by M_inMiddle element is as C=(c_i,j)_m×nThe pixel of corresponding position, as k ≠ 0 K=k-1 is updated, executes step 11~step 13 repeatedly；

Step 14: by C=(c_i,j)_m×nOutput is used as decrypted image.

8. the compound image selection decryption method of a kind of dynamic probability as claimed in claim 7 and null tone domain, feature exist In: by S in step 2_msIt is mapped as sequence S_h=< h₀,h₁,…,h₃₉> specific method be formula (1):

S_h=Draw (S_ms,start,gap,|S_h|) (1)

In formula (1), Draw () is that sequential element extracts function, and wherein start is to extract starting point, and gap is the sample number skipped, | S_h| it is S_hMiddle number of elements, i.e., from S_msCirculation extracts | S_h| a 16 system number is as S_h, start, gap are respectively by formula (2) and formula (3) mapping obtains:

Step 3 is by S_hIt is divided intoTetrameric specific method is formula (4):

Step 3 willBe converted to 10 system decimal G in (0,1) range_i, i=0,1 ..., 3 specific method For formula (5), [] is round function:

Step 4 is by G₃As parameter alpha, G₀,G₁,G₂10 system decimal G ' being mapped as in (0,1) range₀,G′₁,G′₂It is specific Method is by G₀,G₁,G₂Respectively as the input parameter of formula (6), 3 sequential value G ' of formula (6) iteration 1 time generation are substituted into₀,G′₁, G′₂；

By μ in step 5₀As system parameter, x_initThe random number in 5 (0,1) ranges is generated as sequence S as initial value_p =< p₀,p₁,p₂,p₃,p₄> specific method be by μ₀As system parameter, x_initFormula (7) iteration 5 times productions are brought into as initial value Raw sequence S_p=< p₀,p₁,p₂,p₃,p₄>:

x_i+1=μ x_i(1-x_i) (7)；

By S in step 5_pConstruct the interval division sequence S ' in (0,1) range_p=< p '₀,p′₁,p′₂,p′₃,p′₄> specific method For by S_pMiddle element obtains interval division sequence S ' by descending order_p=< p '₀,p′₁,p′₂,p′₃,p′₄>。

9. the compound image selection decryption method of a kind of dynamic probability as claimed in claim 7 and null tone domain, feature exist In: step 6 by Y_init,μ₀The μ being mapped as in [3.57,4] range₁Specific method be formula (8):

Step 6 is by X_initAnd μ₁Respectively as initial value and system parameter iteration 1 time mapping value as intermediate key parameter Z_init Specific method be use formula (7):

x_i+1=μ x_i(1-x_i) (7)；

Step 7 is by X_init,Y_init,Z_init3 real value random number X of chaos system iteration 1 time generation are substituted into as initial value₀,Y₀,Z₀ Specific method be by X_init,Y_init,Z_initAs the initial value of formula (9), formula (9) system parameter takes a=b=0.2, c=5.7, 3 real value random value X of iterative (9) 1 generations₀,Y₀,Z₀:

Step 8 utilizes X₀,Y₀,Z₀To S_idThe specific method being updated is by X₀,Y₀,Z₀It is mapped as by formula (18) and formula (19) Start, gap, right back-pushed-type (20) is to S_idIt is updated, whereinIt is accorded with for downward rounding operation:

S_id=Draw (S_id,start,gap,|S_id|) (20)；

Step 9 utilizes X₀,Y₀,Z₀To μ₀The specific method being updated is formula (22):

Step 9 is to S_ms=< sm_i>₇₂In element be updated operation method particularly includes: first use X₀,Y₀,Z₀It is generated by formula (21) x_init, then by x_init,μ₀Substitution formula (7) iteration generates random sequence S_R=< r_i>₇₂, by formula (23) to S_ms=< sm_i>₇₂In Element is updated operation；

x_init=(X₀+X₀Y₀+X₀Y₀Z₀)mod1 (21)

x_i+1=μ x_i(1-x_i) (7)

10. the compound image selection decryption method of a kind of dynamic probability as claimed in claim 7 and null tone domain, feature exist In: by S in step 11_{X >},S_{Y >}- 1 element of kthIt is mapped as C=(c_i,j)_m×nUpper random point (r₀,v₀) specific side Method is formula (24):

Step 11 is by S_{Z >}- 1 element of kth in sequenceWithThe specific method for being mapped as transformation parameter v is formula (25):

Step 12 is by (r₀,v₀) it is used as starting point, from C=(c_i,j)_m×nFilter out 4 × 4 matrix fritter M_in=(m_u,w)_4×4It is specific Method is formula (26):

Step 12 calculates M_inMapping value Map (M_in) specific method be by formula (12) to calculate M_inCorresponding variance:

By matrix M in step 12_in=(m_u,w)_4×4Decryption is matrix M_outSpecific method be formula (27):

M_out=Decryption (M_in,v,P,f′,S_id,S′_{P >}) (27)

In formula (27), f '={ f '₀,f′₁,…,f′₅It is program event set, f ' corresponds to 6 groups of program events, wherein f '₀,f′₁, f′₂Airspace displacement box program event, as shown in formula (28), f '₃,f′₄,f′₅Transform domain displacement box program event, such as formula (29) institute Show, f '₀,f′₁,…,f′₅Corresponding displacement box Px₀,Px₁,…,Px₅As shown in formula (17):

In formula (28), M_codeIt is number matrix, remembers M_inIn element m_u,wIn Px_iIn number be id, thenLetter The function that number executes is by m_u,wIt is moved to M_codeMiddle element number is the coordinate position of (id-v+16) mod16；

In formula (29), M_HIt is Hadamard transform battle array, Permute₁ ^-1The operation that () executes is will be in Px_iIn number be id ≠ × Element mt_u,wIt is moved to M_codeIt is middle number be (id-v+16) mod16+1 coordinate position, id=× element remain at (0,0) position change does not occur for position；

Step 13 calculates M_outCorresponding mapping value Map (M_out) specific method be to calculate M by the same method of formula (12)_outInstitute Corresponding variance.