针对异构化程度不断加剧的通信网络环境对码率转换能力的需求,提出了一种支持密文域转码的层次化加密算法CT-HEA.与以往基于JPEG2000图像的加密算法相比,CT-HEA针对率失真优化截断模型的特点,按照图像质量层和分辨率对压缩流重新进行截断与合并,对重组后的码流采用密码学算法进行分层加密.该算法支持对加密压缩流的透明码率转换.仿真实验结果表明,CT-HEA算法复杂度低、保密性好,具有灵活的安全转码特性和低的转码代价.Aiming at the increasing demand for transcoding capacity caused by the aggravating isomerization degree in communication networks,a digital image hierarchical encryption algorithm supporting ciphertext domain transcoding named CT-HEA(Ciphertext Transcoding-Hierarchical Encryption Algorithm)was proposed.Compared with the tradi-tional JPEG2000image encryption algorithms,aiming at the feature of rate-distortion optimized truncation model,CT-HEA truncates and combines the compressed codestream according to image quality layer and resolution,applies hierarchical encryption to the codestream after reorganization by using cryptographic algorithms.It supports transparent transcoding operations directly on the encrypted and compressed bitstream.Simulation results demonstrate that CT-HEA is characterized by low complexity,high performance of secure,high secure transcoding flexibility and low transcoding overhead
