Low-cost Chosen Plaintext Attack For Combined Multi-scrambling Image Encryption

With the rapid development of communication and computer technology and the spread of Internet in life,people widely use communication network to transmit images and voice data,so the security of multimedia data has gradually become the focus of research.In many practical applications,secure storage of digital multimedia data is needed,such as enterprise internal teleconference,medical images,pay TV and military imaging,and privacy related multimedia services.In order to meet the security requirements of image data,the reversible data hiding in encrypted image(RDH-EI)technology has been widely concerned.This technology combines image encryption technology and reversible data hiding technology,which can effectively ensure the security of image information in communication.At the same time,the core technology of RDH-EI is to prevent the original image from leaking to the third party attackers,so image encryption is very important for RDH-EI,and it is one of the important means to ensure the image security.Scrambling is widely used in RDH-EI image encryption technology because of its advantages of simple operation and low computational complexity.In order to improve the security,RDH-EI often uses the combination of multiple scrambling to encrypt the image.Aiming at this encryption method,this thesis designs an improved low-cost chosen plaintext attack algorithm,which reduces the attack cost of existing algorithms,that is,the number of plaintext and ciphertext required for the attack,the main contents of this thesis are as follows.A low-cost chosen plaintext attack algorithm based on bit row column scrambling encryption is designed.This thesis first analyzes the impact of the existing encryption algorithm defects on security,and then analyzes the attack principle and defects of the existing plaintext attack algorithm.According to the theoretical basis of the analysis,an improved low-cost chosen plaintext attack algorithm is designed to construct a special image with row column coordinates corresponding to the number and position of "0" or "1" bits.The scrambling matrix of the original encryption algorithm can be estimated by comparing the number characteristics of the constructed image and its corresponding encrypted image.The experimental data show that: the attack algorithm can ensure that the image can be completely restored,while reducing the number of required plaintext pairs from 9 to 2,and compared with the existing attack algorithm,the attack time is reduced,and the minimum time is reduced to 7.476 seconds,which proves the effectiveness of the improved algorithm.A low-cost chosen plaintext attack algorithm based on multiple scrambling image encryption algorithm is designed.This thesis first introduces the existing encryption algorithm,analyzes the potential security defects in the principle of the existing encryption algorithm,then introduces the existing plaintext attack for the encryption method,and analyzes the principle of the algorithm and the shortcomings in the construction of plaintext.Based on this theory,an improved low-cost chosen plaintext attack algorithm is designed.By marking a pair of pixel values and a special block in the image block,the number of plaintext pairs needed to estimate the bit plane scrambling and block scrambling matrix is effectively reduced,at the same time,a plaintext with special intra block pixels is constructed to estimate the intra block pixel scrambling matrix.The experimental results show that: compared with the existing attack algorithm,the improved attack algorithm can effectively reduce the attack cost.In the case of image size and block size,the logarithm of plaintext and ciphertext is reduced from 74 pairs to 2 pairs,and the minimum attack time of the improved algorithm is reduced to 7.713 seconds,which proves the effectiveness of the improved attack algorithm.