基于上下文的分块图像联合压缩加密算法

Joint compression-encryption of block image based on context

为了研究图像压缩与加密同步进行及提高安全性问题,提出了一种基于改进零树结构的分块图像联合压缩加密算法,将图像对应不同分块区域映射到相应子带中。利用密钥对图像压缩产生的原始上下文进行修正,然后与判决一起送往自适应算术编码器实现图像联合压缩加密。由于自适应算术编码的概率跳转规律复杂,相对概率固定的区间分裂算术编码安全性更好。对所提出的算法进行仿真,结果表明:与原始图像压缩算法相比较,所提出的算法具有基本相当的压缩效率;而采用的图像分块方法能够灵活地控制不同区域图像的相对质量及更好地实现信息安全防护;使用不同的密钥可以进行分块加密,实现了对重要信息的隐私和机密保护。

This paper proposed a novel algorithm, in which the data of block regions mapped to the corresponding sub-band coefficients in order to make the image compression and encryption realized simultaneously and improve security. It used the key to modify the original context. And then it sent the modified context and the corresponding decision to arithmetic coder to implement the joint compression-encryption. The security encryption by the adaptive arithmetic coding is better than the one by arithmetic coding based on interval splitting （ACIP）. The distribution of the adaptive arithmetic coding is more complex than the probability distribution of ACIP which is fixed. It simulated the proposed algorithm. The results show that the scheme has the same compression efficiency compared with the original image compression algorithm. The relative quality of different re- gions can be controlled flexibly. It can have a better information security efficiency to use the way of image block. Different keys can be used to encrypt the coefficients of different regions, which can realize the important information privacy and confi- dentiality protection.