In this paper, a novel method for lossless image encryption based on set partitioning in hierarchical trees and cellular automata. The proposed encryption method embeds the encryption into the compression process, in which a small part of the data is encrypted quickly, while maintaining the good coding characteristics of set partitioning in hierarchical trees (SPIHT). The proposed encryption system adopts three stages of scrambling and diffusion. In each stage of encryption, different chaotic systems are used to generate the plaintext-related key stream to maintain high security and to resist some attacks. Moreover, the channel length of the coded-and-compressed color image is more uncertain, resulting into higher difficulty for attackers to decipher the algorithm. The experimental results indicate that the length of bitstream is compressed to 50% of the original image, showing that our proposed algorithm has higher lossless compression ratio compared with the existing algorithms. Meanwhile, the encryption scheme passes the entropy analysis, sensitivity analysis, lossless recovery test, and SP800-22 test.

本文提出了一种基于层次树和元胞自动机中集合划分的无损图像加密新方法。所提出的加密方法将加密嵌入压缩过程中，其中一小部分数据被快速加密，同时保持了分层树（SPIHT）中集合划分的良好编码特性。所提出的加密系统采用加扰和扩散的三个阶段。在加密的每个阶段，将使用不同的混沌系统来生成与明文相关的密钥流，以维持较高的安全性并抵抗某些攻击。此外，编码和压缩的彩色图像的通道长度更加不确定，从而使攻击者解密该算法的难度更高。实验结果表明，比特流的长度被压缩为原始图像的50％，表明与现有算法相比，本文提出的算法具有更高的无损压缩率。同时，该加密方案通过了熵分析，敏感性分析，无损恢复测试和SP800-22测试。