110 results about "Color image encryption" patented technology

The invention discloses a color image encryption and decryption method based on multiple-fractional-order chaotic systems. An encryption algorithm comprises an original image scrambling stage and a scrambling image encryption stage. Firstly, two different fractional-order chaotic systems are utilize to generate three scrambling arrays and respectively process R, G and B three primary color component arrays of an original color image I0 in a scrambling mode to obtain scrambled image I1. Furthermore, another two different fractional-order chaotic systems are utilize to generate three secret key arrays and carries out exclusive OR operation on elements on the secret key arrays and pixel of the scrambled image I1 one by one to change values of all pixel points of the scrambled image I1 to obtain encrypted image I2, and the image decryption is a reversed process of the encryption. The method uses the multiple-fractional-order chaotic systems so as to greatly enhance safety. Furthermore, the algorithm secret keys are large in space, high in secret key sensitiveness and strong in impact resistance.

The invention belongs to the technical field of information security, and particularly relates to a color image encryption method based on cellular neural network hyperchaos and a DNA sequence. The method provided by the invention comprises the steps of separating red, green and blue three primary color components of a color plaintext image; updating and generating parameters and initial values of a six-order cellular neural network hyperchaotic system and a Logistic-Sine mapping system through the plaintext image, respectively carrying out iterative operation on the two chaotic systems, and obtaining red, green and blue components of an encrypted image according to a DNA encoding rule and a DNA decoding rule; and finally, changing the pixel values of the encrypted image through key stream and a bitwise XOR operation to obtain a final ciphertext image. The decryption is a reverse operation of the encryption process. Compared with the existing image encryption method, the color image encryption method provided by the invention has the advantages of high security, good encryption effect, strong robustness, no information loss and the like, and thus being capable of being widely used in military, remote sensing, remote medical treatment, commerce and other fields.

The invention relates to a color image encryption method based on an SHA-384 function, a spatiotemporal chaotic system, a quantum chaotic system and a neural network. The method includes the steps that an original color image I0 is calculated through the SHA-384 function, a Hash value is obtained as a secret key, the Hash value, a CML and one-dimension Logistic chaotic mapping are utilized for generating a chaos sequence, bit-level line-column scrambling is carried out on high four-digit images of components of three primary colors of the I0 through the chaos sequence, and a scrambled image I1 is obtained; the Logistic quantum chaotic system is utilized for generating a chaos sequence for encrypting the scrambled image, and is combined with the neural network to carry out parallel diffusion processing on all pixel values of components of three primary colors of the I1, and a final encrypted image I2 is obtained. By the method, the space of the secret key is greatly enlarged, the safety, encryption effect and secret key sensibility are higher, the attack resistance capacity is higher, the scrambling process and the encryption time are shorter, and hardware implementation is easier.

The present invention relates to a DNA dynamic coding based colored image encryption method, comprising: obtaining a key through a colored plain-text image; by the key, calculating an initial value and a parameter of a chaotic system used in scrambling and diffusion processes; substituting the initial value and the parameter to the chaotic system for iteration to obtain W1 and W2, obtaining a scrambling matrix K from W1, obtaining an integer matrix Y and an index matrix Ind from W2, and performing DNA coding on Y according to the index matrix Ind; and performing scrambling on the plain-text image row by row by using the matrix K, then performing coding and diffusion until all rows finish DNA coding, and finally performing decoding and recomposing on a DNA matrix, to obtain a final colored ciphertext image. According to the method, a function SHA256 is used to generate the key, so that the key space is expanded; the generation of the key depends on a plain-text, so that plain-text attack can be effectively resisted; chaotic characteristics are combined with DNA dynamic coding, so that the security is further improved; and meanwhile, scrambling and diffusion operations are performed according to the row of images, so that parallel computing is facilitated and the efficiency is improved.

The invention relates to a double-random-phase optical color image encryption device and method, which belong to the field of optical image processing technique. The double-random-phase optical color image encryption device comprises an optical image encryption device and an optical image decryption device. The double-random-phase optical color image encryption device has high flexibility by adopting a joint fractional Fourier transform correlator, and the encryption technique based on the joint fractional Fourier transform correlator structure has high safety even if a correct phase mask cannot decrypt the original image information if the position has a slight change due to the translation variability of the fractional Fourier transform. The decryption device can be achieved only by arranging an electronic shutter of the encryption device and using the original illumination parallel light as the light source, and does not generate the optical field distribution conjugated to the encryption process. Based on the parallel processing characteristics of an optical information processing system, the double-random-phase optical color image encryption device can achieve color image encryption and decryption by use of single wavelength. Therefore, the double-random-phase optical color image encryption device has the advantages of simple structure, simplified system, lowered cost, high safe performance, and wide application range, and is convenient in operation.

The invention relates to a color image encrypting method based on a multi-chaos system, which is technically characterized in that the gray value of each pixel of an Input-image is recorded as a two-dimensional matrix P(x,y), S box transformation is performed to the P(x,y), and a transformation result is transformed into a pile of pixel groups P(h*x+y), i.e. P0, P1, P2, P3, to Pn, and the pixel groups are recorded as a sequence Pi; XOR operation is performed to each value of {XL1'} and {XL2'} and each pixel in Pi, i.e. Pi'=Pi +XL2'+XL1', thereby finishing the encrypting process. The invention has the advantages of large key space, high key sensitivity, good security and strong anti-attack ability. The security of the method can be completely independent of the attribute of an image and is especially suitable for the condition with higher security requirement.

A single-channel color image encryption method based on chaos and phase retrieval process comprises a color image chaos scrambling and decomposition step, a pure phase extraction and modulation step and a chaos diffusion step. Combining fractional Fourier transform and paired Logistic chaotic mapping, an encrypted image has nonlinearity and randomness, security and convergence speed of an encryption system are raised, and the problem of slow convergence speed existing in a present encryption method is solved. Meanwhile, complexity of the color image encryption system is reduced, the system is simple, and operation is convenient.

The invention relates to the field of strand displacement, and provides a color image encryption method based on a DNA strand displacement analog circuit. Firstly, a reaction module with a light-emitting group and a quenching group is designed through Visual DSD software, and by utilizing the equivalence of a DNA strand displacement reaction module and an ideal reaction module, an analog circuit formed by the DNA strand displacement reaction module can perform analog on the dynamics characteristics of an ideal reaction network formed by the ideal reaction module, wherein the Rössler chaotic system can be described by the idealized reaction network. Secondly, data generated by the DNA strand displacement analog circuit is converted into a chaotic sequence matched with a plaintext image in size after being extended, and finally, the color image encryption effect is achieved through scrambling and diffusion operations.

The invention discloses a color image encryption method based on dynamic chaos and matrix convolution operation. According to the method, a cloud model and generalized Fibonacci are combined to propose a new composite chaotic system, dynamic random change of a chaotic sequence is realized, and scrambling transformation of pixel point coordinates is performed on spliced images of R, G and B components of a color image by using the chaotic sequence; then, the chaotic sequence value is used as a matrix convolution cloud side for alternately updating an input value and a pixel value of matrix convolution operation, and replacement transformation of an original pixel value is realized; and finally, positive and negative two-way exclusive OR operation is carried out on the replaced pixel value,a cloud model Fibonacci chaotic sequence and the pixel values of the front (rear) adjacent pixel points to realize linkage diffusion transformation of the pixel values of the whole pixel points causedby the change of any pixel value so as to generate encrypted images in sequence. The method has the characteristics of high encryption security, high anti-interference performance, high robustness and the like.

A single channel color image encryption method based on GT conversion and chaos relates to two encryption frames. In the first encryption frame, first, normalization operation is performed on a color image, and the normalized image is decomposed into three red, green and blue component images; then, Arnold conversion is performed on the three component images to perform pixel permutation; finally, Logistic chaotic mapping, tent chaotic mapping and Gyrator conversion with an rotating angle of alpha are used for combining the three component images in chaos into data information relevant to a three-channel structure; in the second encryption frame, first, Arnold conversion is performed on data information relevant to the three-channel structure; then, phase modulation is performed on the Arnold conversion result; finally, Gyrator conversion is performed on a phase modulation result, the encryption process is completed, and gray image information is obtained.

The invention discloses a double color image encryption method based on DNA sequence operation and deformed coupled map lattices. The method comprises: utilizing a secret key and two color plaintext images to generate parameters and initial values of iterating the deformed coupled map lattices, and generating secret key streams of L1, L2, K1 and K2 and random numbers of d1, d2 and d3 through iteration; separating red, green and blue trichromatic components of the plaintext images, transforming the components into binary matrices, and recombining the six binary matrices to obtain recombination matrices of A and B, utilizing the secret key streams of L1 and L2 to carry out bit-level scrambling on the matrices of A and B, and dividing the same into six binary matrices; utilizing a DNA encoding rule and combining the random numbers of d1, d2 and d3 to transform the binary matrices into DNA matrices, and executing DNA addition, subtraction and exclusive OR operations; and utilizing a DNA decoding rule to transform the DNA matrix into decimal matrices, utilizing the secret key streams of K1 and K2 and the bitwise exclusive OR operation to change values of image pixels, and obtaining ciphertext images of C1 and C2. The method can encrypt the two plaintext images at the same time, and has the advantages of high security, good encryption effect, no information loss, fast encryption speed and the like.

The invention provides a color image encrypting and embedding method based on a discrete domain and relates to digital image processing techniques. The method comprises the steps of introducing a secret image feature coefficient to Logistic chaotic mapping and Rabinovich hyperchaotic mapping and making generated sequences associated with the secret image; rearranging the RGB order of the image byusing the generated Logistic chaotic sequences to eliminate color information of the color image; encrypting the image pixel positions by using a group of sequences in four groups of chaotic sequencesgenerated by Rabinovich hyperchaotic mapping, and using a block scrambling method to encrypt the image quickly; scrambling and diffusing a low frequency coefficient obtained after discrete wavelet transform (DWT) of the image by using the remaining three groups of Rabinovich hyperchaotic sequences in different channels; embedding the encrypted image into a DWT high frequency coefficient of a public image by using the least significant bit replacement algorithm (LSB). The method can effectively protect the existence of image information and guarantees the security of an image in a communication process on the basis of protecting the security of image content.

The invention relates to a color image encryption method based on Latin square scrambling. Plaintext keys r1, g1 and b1 are calculated through utilization of R, G and B components of a color plaintextimage, an initial value and a parameter obtained through calculation based on the keys are substituted into a chaotic system, and three groups of chaotic sequences are generated; the chaotic sequences for scrambling and diffusion are selected through utilization of a chaotic sequence selection mechanism based on the plaintext and digital arrangement; and a final ciphertext image is obtained through adoption of a block scrambling policy based on a Latin square and the chaotic sequences, and diffusion operation based on the plaintext and a scrambled image. The encryption method is closely related to the plaintext, so the plaintext attack resistance is improved. The employed chaotic system is an improved chaotic system, a chaotic characteristic is good, the randomness is high and a key spaceis great, so a security level is further improved. A simulation result and safety analysis show that according to the encryption provided by the invention, an image complete encryption demand can besatisfied, the encryption efficiency is high, and the robustness is high.

The invention discloses an RGB color image encryption method based on inverse difference chaotic mapping, and belongs to the field of cryptology and information security. The method comprises the following steps: inputting an original RGB color image P, selecting a parameter and an initial value of inverse difference chaotic mapping as a secret key K, presetting to carry out T rounds of encryptionoperation, and using the secret key K to iterate inverse difference chaotic mapping to generate a chaotic pseudo-random sequence; performing arrangement operation on the chaotic pseudo-random sequence, and performing corresponding inverse difference chaotic mapping scrambling on the image data of the plaintext image P to change the positions of pixel points to obtain a scrambled image; discretizing the chaotic pseudo-random sequence to obtain a discrete random sequence, and performing exclusive-OR operation on the discrete random sequence and the scrambled image to change the gray value of the pixel point to obtain a mixed image; and returning the mixed image to carry out scrambling processing and mixing processing, and repeating the operation to a preset value T to carry out encryption operation to obtain a ciphertext image E. The encryption method is high in safety, large in secret key space and high in calculation implementation speed.

The embodiments of the present invention disclose a color image encryption method and a device. The method comprises the following steps of subjecting a RGB component of a to-be-encrypted plaintext color image to the two-dimensional pixel scrambling treatment by using a non-periodic two-dimensional Cat transformation with a pixel value to be unchanged; subjecting the gray value of each pixel of the plaintext color image after the scrambling treatment to the operation of XOR together with three groups of chaotic sequences obtained through the mapping of Henon_Kent so as to obtain intermediate ciphertext components; subjecting an intermediate ciphertext matrix formed by intermediate ciphertext components to the gray value exchange of pixels by using the non-periodic three-dimensional Cat transformation, and iteratively conducting the operation for t times (t is a positive integer); successively circulating and executing the above steps for T times (T is a positive integer), and outputting the encrypted image of the plaintext color image. The key space is enlarged, so that the security of color image encryption is improved. The method and the device are good in robustness, and variousattack means can be effectively resisted.

An encryption method based on iteration FrFT and chaotic single-channel color images is characterized by comprising the steps that firstly the color images are placed in chaos and divided into three parts, then two parts are encrypted to obtain a middle result, and finally the amplitude of the middle result and the third part are encrypted to obtain a final cryptograph. The FrFT and the paired Logistic chaotic mapping are combined, so that the encrypted image has the nonlinearity and randomness, the safety and convergence rate of an encryption system are improved, the problem that an existing encryption method is low in convergence rate is solved, meanwhile, the complexity of the color image encryption system is reduced, the system is simple, and operation is convenient.

The invention relates to the technical field of information security and optical information processing. In order to realize single channel encryption of a color image, greatly reduce the complexity of a cryptosystem, greatly increase a key space, improve the security of the system, enable the management and transmission for random phase plate keys become very convenient and effectively resist common cryptology attacks, the technical scheme employed by the invention is a single channel color image encryption method based on discrete wavelet transform and chaotic double random phase encoding. The method comprises the following steps that 1), according to an encryption part of the image, a to-be-encrypted color image is decomposed into three color channels: read R, green G and blue B, and then a gray carrier image is decomposed into four bands through discrete wavelet transform; 2), according a decryption part of the image, inverse transformer of secondary Gyrator transform is carried out on an encrypted image and then the encrypted image is modulated by a conjugate plate of a second chaotic random phase plate. The method is mainly applied to an information security occasion.

The invention provides a color image encryption method based on three-dimensional Logistic mapping and generalized Cat mapping, which comprises the following steps: reading an original color image toobtain two-dimensional pixel matrixes corresponding to R, G and B components, and straightening the two-dimensional pixel matrixes to obtain three pixel sequences; three groups of chaotic sequences are generated through three-dimensional Logistic mapping iteration, and subjecting the three groups of chaotic sequences and the three pixel sequences to XOR operation to realize diffusion processing; carrying out data reconstruction on the chaotic sequence obtained after diffusion processing and expanding the chaotic sequence into a three-dimensional cube; performing position scrambling processingon the three-dimensional cube through generalized Cat mapping; and converting the three-dimensional cube with the scrambled position into a cuboid which is a ciphertext image. According to the method,parameters and initial values of three-dimensional Logistic mapping and generalized Cat mapping and the plaintext image size are used as keys, the key space is increased. Encryption safety is improved, and the method has the advantages of being high in key sensitivity, high in anti-attack capability and the like.

The invention relates to the technical field of information security and optical information processing, and aims to greatly reduce the complexity of an encryption system. The security of the system is improved, and common cryptography attacks can be effectively resisted. Therefore, the single-channel color image encryption method based on vector decomposition and phase encoding comprises the following steps: (1) an image encryption part: firstly decomposing a color image to be encrypted into three color channels, namely red R, green G and blue B; Carrying out first three-dimensional chaotic random phase mask modulation on the synthesized grayscale image, carrying out first Gyrator transformation on the modulated image, and then carrying out second Gyrator transformation on the modulated image, so that the transformed image is a final encrypted image; And (2) an image decryption part: firstly, carrying out inverse transformation of Gyrator transformation for the second time on the encrypted image, and integrating the three color channels together to obtain a decrypted color image. The method is mainly applied to an optical information encryption and decryption processing occasion.

The invention discloses a color image encryption method based on a fractional order discrete neural network and DNA operation. The method comprises the following steps: S1, establishing an initial value; s2, scrambling pixels among the three color components R, G and B; s3, calculating a DNA code; s4, in order to further improve the encryption security, giving a plaintext-independent DNA diffusionalgorithm based on DNA operation; s5, carrying out secondary scrambling and XOR, wherein secondary scrambling is used for disturbing the positions of elements in the three signal channels. The methodhas the advantages that 1, the problems that the dynamic behavior is not complex enough and the secret key space is small due to the fact that an integer order chaotic system is used in traditional chaotic encryption are solved; 2, the problems of single encryption rule and insensitivity to plaintexts and secret keys of partial DNA encryption algorithms are solved; and 3, the problem that the ciphertext cannot resist noise and information loss attacks in the transmission process is solved; and 4, noise and shear attacks can be dealt with.

The invention provides a chaos-based quick color image encryption method. According to the method, a scrambling key and a substitution key are initialized; to-be-encrypted image pixels are marked as aone-dimensional array; a chaotic sequence of a hyperchaotic Lu system is generated; quantification processing is performed on the chaotic sequence to obtain a scrambling key stream; scrambling operation is performed on the array of the to-be-encrypted image pixels according to the scrambling key stream permKstr; the substitution key is used as a state variable initial value of logistic chaotic mapping for logistic mapping iteration, and three substitution key stream elements are generated according to a current state variable value of logistic chaotic mapping to encrypt three sub-pixels of one pixel point of the array imgDatal after scrambling operation; and the to-be-encrypted image pixels are encrypted multiple turns, and an encrypted array is obtained. In this way, encryption efficiency is remarkably improved; by introducing a plaintext-based chaotic orbit disturbance mechanism, the key stream is relevant to a plaintext, the ability of an encryption system in resisting selection ofa plaintext attack is enhanced, and meanwhile the random statistical characteristic of the chaotic key stream sequence is improved.

The invention relates to a color image encryption system and an encryption and decryption method based on compression holography and belongs to the technical field of optical image encryption. The system comprises a laser device, a first reflecting mirror, a second reflecting mirror, a beam expanding and collimating system, a beam splitter, a first spatial light modulator, a second spatial light modulator, a third spatial light modulator, a fourth spatial light modulator, a first random phase mask, a second random phase mask, a third random phase mask, a high-speed image collecting device and a computer. Firstly, gray level images of three channels of color images are extracted and are arranged at the positions with different distances to a CCD to serve as object information needing to be encrypted, the three random phase masks are tightly attached to the three gray level images and then are used for modulating light beams containing the object information, the three light beams are interfered by a beam combining prism and reference light to generate a holographic image, and the gray level images of the three channels are simultaneously encrypted on the same holographic image. Lastly, decryption is carried out with a TwIST algorithm, and color image composition is carried out. According to the color image encryption system and the encryption and decryption method based on the compression holography, the color images can be encrypted through one-time exposure, and the encryption efficiency and the confidentiality degree of the encrypted information are improved.

The invention provides a color image encryption method based on dynamic DNA and 4D chaos, aiming at solving the technical problem of image encryption based on traditional static DNA. The method comprises: using 4D chaos to generate two groups of four chaos matrixes which respectively correspond to a DNA confusion operation and a dynamic DNA coding matrix of three channels of red, green and blue,and a rule matrix and a chaos matrix of a dynamic DNA diffusion operation of the three channels. Due to the fact that the initial parameters of the 4D chaos are determined by the Hash algorithm and the plaintext, the encryption method can resist plaintext selection attacks, and dynamic DNA encryption can be achieved. The method is high in robustness and good in safety.

The invention discloses a lossless color image encryption method based on a hyperchaotic system. The lossless color image encryption method comprises the following steps: separating a color image to be encrypted into a three-primary-color component matrix; processing the three-primary-color component matrix through a hyperchaotic system to obtain an original chaotic sequence; training the originalchaotic sequence by using a BP neural network, and outputting a new chaotic sequence; eliminating a transient effect and encrypting by combining the new chaotic sequence; converting the image encrypted in the step 4 into a frequency domain space through two-dimensional discrete wavelet transform to obtain a corresponding sub-band; scrambling and encrypting the sub-bands of the frequency domain space; performing two-dimensional discrete wavelet inverse transformation on the scrambled and encrypted sub-bands, and converting the scrambled and encrypted sub-bands into a spatial domain to obtain aciphertext image of three primary colors; and combining the ciphertext images of the three primary colors to obtain an encrypted color image. According to the method, the security of the image encryption algorithm is effectively improved, and attack means which are difficult to resist at present, such as plaintext attack selection, can be effectively resisted.

The invention belongs to the technical field of information security, and particularly relates to a color image encryption method based on compressed sensing and deformation coupling mapping lattices,which comprises the following steps: separating three primary color components of a color plaintext image to obtain a component matrix; updating parameters and initial values of the deformation coupling image grids through an SHA-256 function in combination with the initial key, and obtaining a measurement matrix and a key stream through an iterative space-time chaotic system; segmenting the component matrix and obtaining a new image matrix; generating a sparse dictionary for the new image matrix; measuring a new image by using the measurement matrix to obtain an intermediate image; converting the intermediate image into a coefficient matrix, and executing scrambling and diffusion operations in a frequency domain to obtain a scrambling diffusion matrix; and performing pixel-level diffusion operation on the scrambling diffusion matrix by using the key stream matrix to obtain a final ciphertext image. Statistics, known and selected plaintexts, selected ciphertext attacks and the like are effectively resisted, the safety and the encryption effect are improved, and the method has a good application prospect.

The invention belongs to the technical field of information security and particularly relates to a color image encryption method based on a hybrid domain and an LSS type coupled map lattice. The method comprises the steps of inputting a color plaintext image, separating red, green and blue three primary color components of the plaintext image to obtain corresponding three matrixes, generating a parameter and an initial value of the LSS type coupled map lattice through combination of a key, and generating key streams through utilization of the LSS type coupled map lattice; carrying out two-dimensional discrete wavelet transform on the three matrixes to obtain three groups of sub-bands; keeping a high and low frequency sub-band unchanged, scrambling the other sub-bands through utilization ofthe key streams, and shrinking the scrambled sub-bands; switching the content of the shrunk sub-bands; carrying out the two-dimensional discrete wavelet transform on the three groups of sub-bands toobtain three encryption components; and blocking the three encryption components, and carrying out bit level diffusion operation on the blocked matrixes through utilization of the key streams to obtain a ciphertext image. According to the method, statistics attacks, known and chosen plaintext attacks and chosen ciphertext attacks can be effectively resisted.

The invention relates to a new intersected composite chaotic color image encryption algorithm which can rapidly encrypt an original image. The algorithm mainly relates to two kinds of chaotic encryption ideas, namely, spatial domain scrambling and pixel value diffusion. The algorithm carries out pixel scrambling and diffusion after a to-be-encrypted color image is subjected to pretreatment. The algorithm applies a composite new chaotic encryption sequence to an image encryption method which carries out scrambling, diffusion and re-scrambling. The experiment shows that the algorithm has high safety than other algorithms in color image encryption.

The invention belongs to the technical field of information security and optical information processing, and provides a single-lens color image encryption system for solving the problem that a first random phase mask cannot play a role of secret key when an image is a real value in the aspect of an optical system, and solving the problem of secret key management, transmission and updating in the aspect of a secret key generation method. The technical scheme adopted by the invention is that the single-lens color image encryption system comprises four parts including (1) a secret key generation part, (2) an image encryption part, (3) a secret key transmission part and (4) an image decryption part, wherein a first random phase mask is generated by a Duffing chaotic system, and a second random phase mask is generated by a Tinkerbell chaotic system; the image encryption part can obtain an encrypted color image by integrating three encryption channels; and the secret key transmission part selects an RSA public key algorithm for encrypting a secret key used in the part (2), so as to ensure the security of secret key transmission. The single-lens color image encryption system is mainly applied to information security and optical information processing occasions.

The invention relates to the information safety and light information processing technology field and provides a color image encryption and hiding method based on PT-LCT and discrete wavelet transform-singular value decomposition (DWT-SVD). Finally, a color carrier image including a secret image is acquired. The color image encryption and hiding method based on PT-LCT and DWT-SVD is characterized by firstly, encrypting a color image to be hidden through Arnold scrambling and a PT-LCT system; then, converting the color carrier image from an RGB color space into a YCbCr space; and then, embedding the encrypted color image into Cb and Cr channels through a DWT-SVD method; and finally, converting the Cb and Cr channels including the secret image and a Y channel into the RGB color space so that the color carrier image including the secret image is acquired. The method is mainly applied to an information safety and light information processing occasion.

The invention provides a color image encryption method based on circuitous cylindrical diffraction and phase preservation truncation. According to the method, a complex combination of any two components in the red, green and blue components of a color image is encrypted by using the circuitous cylindrical diffraction process, two pseudo-random phase plates are respectively loaded on an object surface and an intermediate diffraction surface; the complex amplitude distribution obtained by cylindrical diffraction is separated by adopting a phase preservation truncation method to obtain an amplitude portion and a phase portion, two phase portions obtained by performing phase preservation twice serve as two decryption keys, complex combination is performed on the amplitude obtained by the firsttime of phase truncation and another component of the color image, the amplitude obtained the second time of phase truncation serve as ciphertext output. The method realizes asymmetric encryption byusing cylindrical diffraction and phase truncation, can solve three problems such as a linear system, complex value output and information leakage at the same time, and greatly improves the security of the encryption system.