CN113364573B - Chaotic image encryption and transmission method based on public key system and Hash algorithm - Google Patents

Abstract

The invention provides a chaotic image encryption and transmission method based on a public key system and a hash algorithm, including an ECC-based comprehensive encryption scheme and a hash algorithm, which synthesizes a ciphertext image and an encrypted hash value into an encrypted data packet and performs transmission, and give an example under a fast dynamic block image encryption scheme, emphasizing the transmission process of the transmission scheme under the public channel and the reliability of the method, wherein the public key encryption algorithm based on ECC can be arbitrary Choice, the hyperchaotic system and the encryption and decryption schemes can be replaced arbitrarily, and the diversified system design makes the present invention have strong flexibility and reliability.

Description

Chaotic Image Encryption and Transmission Method Based on Public Key System and Hash Algorithm

technical field

The invention belongs to the technical field of image encryption, and relates to a chaotic image encryption and transmission method based on a public key system and a hash algorithm.

Background technique

For text, voice, image, video and other data transmitted in public channels, data security issues and transmission schemes have always been difficult points in scientific research. Public-key cryptography can be used to encrypt data, perform digital signatures, or exchange keys at the beginning of secure communication. Because of its asymmetry, this method can resist chosen-plaintext attacks and chosen-ciphertext attacks well. The existing popular image encryption algorithms are all carried out under the structure of scrambling-diffusion. Relevant documents or patents generally only provide encryption and decryption schemes, and do not give specific methods for actual application scenarios or transmission under public channels. . In addition, the existing algorithms all have a common feature: symmetry, which makes the key vulnerable to attack when it is transmitted on a public channel. Therefore, the present invention uses an asymmetric method to separate the public key from the private key, which can effectively solve this problem.

The hash algorithm is widely used to generate the initial value of the chaotic sequence. The usual practice is that the sender uses the plaintext image to obtain the hash value, and then uses the hash value for encryption. In order to decrypt the image, when passing the encrypted image, it needs to be passed along with the hash value. The defect of this method is that since the hash value is related to the plaintext, an attacker can obtain the plaintext information through the hash value, resulting in a greatly reduced security of the ciphertext. Therefore, the present invention also encrypts the hash value, which will be able to fix it.

Image encryption schemes based on discrete or continuous chaos generally require multiple rounds of scrambling-diffusion operations in order to achieve a good encryption effect. In the latest research, due to the complex dynamic behavior of the hyperchaotic system, only one round of diffusion can achieve reliable encryption.

In view of the above objective challenges or existing problems, the present invention proposes an image encryption and transmission scheme based on elliptic curve cryptography (ECC) and hash algorithm, which improves encryption efficiency and transmission security.

Contents of the invention

The purpose of the present invention is to address the problems existing in the prior art, to provide a chaotic image encryption and transmission method based on a public key system and a hash algorithm, which solves the problem that the key is very vulnerable to attacks during public channel transmission, resulting in security and transmission efficiency lower question.

For this reason, the present invention takes the following technical solutions:

A chaotic image encryption and transmission method based on a public key system and a hash algorithm, comprising the following steps:

S1: The receiver generates a key pair and sends the key pair to the sender. The key pair includes a public key and a private key, wherein the public key is used to encrypt data, and the private key is used to decrypt data;

S2: The sender uses the public key and ECIES to encrypt the hash value, encrypts the plaintext image according to the encryption scheme, and synthesizes the two into an encrypted data packet. After the above operations are completed, the sender sends the encrypted data packet to the receiver through the public channel;

S3: After receiving the encrypted data packet, the receiver disassembles the encrypted data packet into an encrypted image and an encrypted hash value. The encrypted hash value is decrypted by the private key and ECIES, and then the decrypted hash value is used for decryption Plaintext images are fine.

Further, the method for combining the hash value and the encrypted plaintext image into an encrypted data packet includes a scrambling process and a diffusion process, and after the scrambling process is completed, a diffusion operation is performed, wherein the scrambling process includes the following steps:

S1: For a plaintext image P with a size of M×N, first convert it from the original pixel-level format to 5 bit-level planes, the set of planes includes a set of low 1-4 bits of all pixels in the original image. The combined plane and four planes composed of bits 5-8 in turn;

S2: After completing the conversion of the picture, for each plane in the plane set, if it contains more information than other planes, it will be divided into smaller blocks. Specifically, it will be divided into smaller blocks by The plane composed of the 8th bit is divided into several 1×1 blocks, the plane composed of the 7th, 6 and 5 bits is divided into several 2×2, 4×4 and 8×8 blocks, and all pixels of the original image are divided into The plane composed of the lower 1-4 bits is divided into 16×16 blocks;

S3: Since the divided plane is equivalent to a matrix composed of divided blocks, continue to perform row shift operation and column shift operation on the above matrix, and the shift distance is determined by the hyperchaotic sequence ;

S4: Combine the above five scrambled planes together and convert them into an image in pixel-level format, and the size is M×N.

Further, the diffusion process includes the following steps:

S1: On the basis of the generated chaotic sequence, generate a sub-chaotic sequence for diffusion operation. The parent sequence used to generate the sub-chaotic sequence is x(i), and the sub-sequence will be generated from x(i), Convert the subsequence into a two-dimensional sequence x(i,j) with a size of M×N;

S2: The association between each pixel in the picture PM(i,j) after the scrambling process and its adjacent pixels on the right and below will be through the relationship between pixel values and the two-dimensional sequence x(i,j) An XOR operation is established, and what is generated after the diffusion process is the final encrypted picture C(i,j).

Further, the displacement distance is calculated by the following formula:

row = floor(mod(rowChao(indexRow2 + n)×10 ⁴ , indexCol))

col = floor(mod(colChao(indexCol2 + n)×10 ⁴ , indexRow))

Among them, indexRow and indexCol represent the number of blocks in the row and the number of blocks in the column respectively, rowChao and colChao are two generated chaotic sequences, n represents the serial number of the current row or the current column, floor(x) represents the largest but An integer not greater than x.

The beneficial effects of the present invention are:

1. The present invention proposes an asymmetric public key system image encryption transmission scheme, which separates the public key from the private key, so that the encrypted image can be safely transmitted in the public channel. In addition, the present invention uses hyperchaotic Sequence, compared with chaotic sequence, its dynamic behavior is more complex and safer;

2. The present invention only needs one round of scrambling-diffusion fast dynamic block image encryption algorithm in the encryption process, which can improve the encryption efficiency;

3. In the present invention, the ECC-based public key encryption algorithm can be selected arbitrarily, and the hyperchaotic system and encryption and decryption schemes can also be replaced arbitrarily. The diversified system design makes the present invention have strong flexibility and reliability.

Description of drawings

Fig. 1 is a schematic diagram of the transmission process of the present invention;

Fig. 2 is a schematic diagram of the encryption process of the present invention;

Fig. 3 is a schematic diagram of plane transformation of the scrambling process in the embodiment of the present invention;

Fig. 4 is a block schematic diagram of the scrambling process in the embodiment of the present invention;

FIG. 5 is a schematic diagram of matrix shifting in an embodiment of the present invention;

Fig. 6 is the schematic diagram of the diffusion process in the embodiment of the present invention;

Fig. 7 is a schematic diagram of a diffusion algorithm in an embodiment of the present invention.

Detailed ways

The technical solutions of the present invention will be described below in conjunction with the accompanying drawings and implementation methods.

As shown in Figures 1 and 2, the chaotic image encryption and transmission method based on the public key system and the hash algorithm includes the following steps:

S1: The receiver generates a key pair and sends the key pair to the sender. The key pair includes a public key and a private key, wherein the public key is used to encrypt data, and the private key is used to decrypt data;

S2: The sender uses the public key and ECIES to encrypt the hash value, encrypts the plaintext image according to the encryption scheme, and synthesizes the two into an encrypted data packet. After the above operations are completed, the sender sends the encrypted data packet to the receiver through the public channel;

S3: After receiving the encrypted data packet, the receiver disassembles the encrypted data packet into an encrypted image and an encrypted hash value. The encrypted hash value is decrypted by the private key and ECIES, and then the decrypted hash value is used for decryption Plaintext images are fine.

Wherein, the method of combining the hash value and the encrypted plaintext image into an encrypted data package includes a scrambling process and a diffusion process, and after the scrambling process is completed, the diffusion operation is performed.

Specifically, the scrambling process includes the following steps:

S1: As shown in Figure 3, convert the plaintext image into 5 different planes, one of which is composed of the 1st to 4th bits of each pixel in the plaintext image, and the remaining four planes are composed of Composed of the 5th-8th bits;

S2: Divide the above plane into blocks of different sizes according to the total amount of information contained in each bit. Since the 8th bit plane contains more information than any other plane, the size of the block is 1×1. When the length of the plane When both and width are multiples of 16, the 7th, 6th, and 5th bit planes will be divided into 2×2, 4×4, and 8×8 blocks in turn, otherwise, the planes will be filled with 0. For the combination Plane, because it contains the least amount of information, in order to improve time efficiency, the size of 16×16 is used for block division;

As shown in Figure 4, the figure shows the process of dividing a 7th bit plane example. In this process, the example plane is divided into several blocks with a size of 2×2. For the convenience of description, the From the right and from top to bottom, the divided blocks are named A-P in turn;

S3: In order to ensure randomness and the relationship with the plaintext image, the previously generated hyperchaotic sequence is used to determine the shift distance during the shifting process. In order to avoid the insecurity caused by excessive use of the sequence, the following formula is used to calculate the shifted distance:

row = floor(mod(rowChao(indexRow2 + n)×10 ⁴ , indexCol))

col = floor(mod(colChao(indexCol2 + n)×10 ⁴ , indexRow))

Among them, indexRow and indexCol represent the number of blocks in the row and the number of blocks in the column respectively, rowChao and colChao represent the two generated chaotic sequences, n represents the serial number of the current row or the current column, floor(x) represents The largest integer not greater than x.

As shown in Figure 5, after the shift distance is determined, the shift operation is as shown in the figure: after the block, all matrix rows will be shifted sequentially according to the previously calculated shift distance, and then all columns will also be shifted according to A similar process is performed for shifting.

S4: Combine all five scrambled planes into a pixel-level image with a size of M×N. This process is essentially the reverse process of S1. So far, the scrambling process is completed.

The steps of the diffusion process are as follows:

S1: On the basis of the generated chaotic sequence, the sub-chaotic sequence used for the diffusion operation is generated based on an already generated chaotic sequence, assuming that the parent sequence selected for generation is x(i), a certain sub-sequence will be generated from x(i). After generating the required subsequence, the subsequence will be converted into a two-dimensional sequence x(i,j) with a size of M×N;

S2: As the input of the diffusion part, each pixel in the picture PM(i,j) after the scrambling process will be associated with the adjacent pixels on the right and below through the pixel value and the two-dimensional sequence x The XOR operation of (i,j) is established, and the final encrypted picture C(i,j) is generated after the diffusion process.

As shown in Figure 6, if the pixel to be operated is located in the lower right corner of the image, it will be XORed with the value of the corresponding position in the two-dimensional chaotic sequence x(i, j) to obtain the value of the ciphertext; if the pixel to be operated Located on the rightmost or bottom row, it first needs to perform XOR operation with the value of the corresponding position in the two-dimensional chaotic sequence x(i,j), and then perform XOR operation with the pixel value of the adjacent pixel on the right or below. Calculate the value of the ciphertext; for a pixel with adjacent pixels on the right and below, compare its pixel value with the value of the corresponding position in the two-dimensional chaotic sequence x(i,j), and the value of the adjacent pixel on the right with the adjacent pixel below The values of are sequentially XORed and transported to obtain the corresponding ciphertext value.

As shown in Figure 7, the process of the above algorithm is: for the picture to be operated, starting from the pixel in the lower right corner, from right to left, from bottom to top, carry out the same two-dimensional chaotic sequence x(i, j) and adjacent pixels. XOR operation, after the pixel in the upper left corner is executed, the entire algorithm flow is executed.

After encrypting the plaintext image, the hash value used to generate the chaotic system will be encrypted based on the public key received from the receiver through ECIES, and the encrypted hash value and ciphertext image will be combined into an encrypted Data packets are used for final transmission, and the generation of encrypted data packets means the end of the entire encryption process.

Claims (1)

1. The chaotic image encryption and transmission method based on the public key system and the Hash algorithm is characterized by comprising the following steps of:

s1: a receiver generates a key pair and sends the key pair to a sender, wherein the key pair comprises a public key and a private key, the public key is used for encrypting data, and the private key is used for decrypting data;

s2: the sender encrypts a plaintext image according to an encryption scheme by using the public key and the ECIES encrypted hash value, combines the encrypted plaintext image and the encrypted image into an encrypted data packet, and sends the encrypted data packet to the receiver through a public channel after the operation is finished;

s3: after receiving the encrypted data packet, a receiver disassembles the encrypted data packet into an encrypted image and an encrypted hash value, wherein the encrypted hash value is decrypted by a private key and an ECIES, and the decrypted hash value is used for decrypting a plaintext image;

the method for combining the hash value and the encrypted plaintext image into the encrypted data packet comprises a scrambling process and a diffusion process, and after the scrambling process is finished, the diffusion operation is executed, wherein the scrambling process comprises the following steps:

s1: for a plaintext image P with the size of M multiplied by N, firstly converting the plaintext image P from an original pixel level format into 5 bit level planes, wherein a plane set comprises a plane formed by combining lower 1-4 bits of all pixels of the original image and four planes formed by sequentially forming 5-8 bits;

s2: after the conversion of the picture is completed, for each plane in the set of planes, if it contains more information amount than the other planes, it is divided into smaller blocks, specifically, the plane composed of the 8 th bit is divided into several 1 × 1 blocks, the plane composed of the 7 th, 6 th and 5 th bits is divided into several 2 × 2, 4 × 4 and 8 × 8 blocks, and the plane composed of the lower 1-4 bit of all the pixels of the original image is divided into 16 × 16 blocks;

s3: because the divided plane is equivalent to a matrix consisting of divided blocks as a unit, the matrix is continuously subjected to row shift operation and column shift operation, and the shift distance is determined by the hyperchaotic sequence;

s4: combining the five scrambled planes together and converting the combined planes into an image in a pixel-level format, wherein the size of the image is M multiplied by N;

the diffusion process comprises the following steps:

s1: generating a sub-chaotic sequence for diffusion operation on the basis of the generated chaotic sequence, wherein a parent sequence for generating the sub-chaotic sequence is x (i), and after the sub-sequence is generated from the x (i), the sub-sequence is converted into a two-dimensional sequence x (i, j) with the size of M multiplied by N;

s2: the association of each pixel in the picture PM (i, j) after the scrambling process and adjacent pixels at the right and below of the pixel is established through the XOR operation between the pixel values and the two-dimensional sequence x (i, j), and a final encrypted picture C (i, j) is generated after the diffusion process;

the shift distance is calculated by the following formula:

row = floor(mod(rowChao(indexRow2 + n)×10 ⁴ , indexCol))

col = floor(mod(colChao(indexCol2 + n)×10 ⁴ , indexRow))

wherein indexRow and indexCol represent the number of blocks in a row and the number of blocks in a column, respectively, rowChao and colChao are two generated chaotic sequences, n represents the number of sequence numbers of a current row or a current column, and floor (x) represents the largest integer but not larger than x.

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