关键词: 数据压缩, 图像加密, Huffman编码, 耦合映像格子

Abstract: This paper proposed a Secure LZW (SLZW) coding algorithm, where encryption was embedded into the improved LZW coding process, and SLZW can fulfill compression and encryption in a single step. In SLZW algorithm, dynamic Huffman tree was utilized to code the dictionary of LZW, and the initialization and updating of Huffman tree were controlled by a sequence of keystream generated by Coupled Map Lattcie (CML). The code words were further XORed with the keystream to generate the ciphertext. The SLZW was applied to GIF image encryption. The experimental results and their analyses indicate that the proposed SLZW algorithm not only has good security, but can also improves the compression ratio by about 10%. Therefore, SLZW can find its wide applications in practice.

Key words: data compression, image encryption, Huffman coding, Coupled Map Lattcie (CML)