JPEG image encryption method compatible in format and invariant in size

Abstract

The present invention provides a JPEG image encryption method compatible in format and invariant in size, and belongs to the technical field of multimedia information safety. The method of the presentinvention includes three encryption steps: 1) classifying and scrambling AC coefficient-encoded zero runs; 2) grouping and scrambling DC coefficient-differentially encoded adjacent same symbols; 3) grouping and iteratively encrypting DC coefficient differential codes. According to the invention, the method can be used for protecting the safety and the privacy of military images, commercial images, medical images or personal images when the images are transmitted through a public channel or stored in the public cloud. The method aims to improve the ubiquitous defect that the size of a ciphertext image increases and the format compatibility of the image is not ideal based on existing JPEG image encryption methods. The above method can resist the known-plaintext attack, and substantially maintain the size of the ciphertext image to be unchanged. Meanwhile, the format compatibility is better and the encryption strength is adjustable.

Description

technical field [0001] The invention belongs to the technical field of multimedia information security, and relates to a JPEG image encryption method with compatible format and constant size. Background technique [0002] With the continuous development of the Internet and the rapid popularization of mobile terminals, image applications are becoming more and more extensive. How to effectively protect the security and privacy of military images, commercial images, medical images or personal images when they are transmitted or stored in cloud space through open channels has attracted more and more attention. [0003] Image encryption is a common method of protecting images. The encryption algorithm converts a plaintext image into a noisy ciphertext image under the control of the key. Only with the correct key can the original plaintext image be decrypted from the ciphertext image; without the correct key, the attacker cannot obtain any relevant information about the content ...

AI Technical Summary

Problems solved by technology

At present, the existing JPEG image encryption algorithms generally have problems such as increased ciphertext image size or poor format compatibility.

[0005] A JPEG image encryption algorithm based on DCT coefficient classification address mapping proposed by Li et al. (Li S, ZhangY. Quantized DCT Coefficient Category Address Encryption for JPEG Image. KSIITransactions on Internet & Information Systems, 2016, Vol. 1806) will destroy the statistical correlation between adjacent DC coefficients, affect the efficiency of differential predictive coding of DC coefficients, and generate ciphertext images of increased size

[0006] A JPEG image encryption algorithm based on bitstream XOR proposed by Qian et al. (Qian Z, Zhang X, WangS. Reversible Data Hiding in Encrypted JPEG Bitstream. IEEE Transactions on Multimedia, 2014, Vol. ) can keep the size of the ciphertext image unchanged, but there are potential problems such as the quantization step size of the ciphertext image being zero and DC coefficient overflow, and the compatibility with the JPEG standard is not ideal

Images