目前基于混沌系统的彩色图像加密算法并未充分地考虑图像时频域特征, 并且具有密钥空间小的缺点, 对此提出了一种基于离散正交S变换域的彩色图像编解码技术。将图像分解为RGB三色通道, 对每个通道分别进行离散正交S变换(DOST); 对各通道使用一级离散小波变换(DWT), 将每个通道分解为四个子带; 使用 DWT分解各子带; 对奇异值进行乘法运算, 使用新奇异值重构所有的子带。可将DOST的子带数量、奇异值参数以及DWT子带的排列顺序作为密钥, 从密钥获取难度极高。实验结果表明, 方法具有较好的加密效果, 安全性优于其他的算法。

The existing chaotic system based color image encryption algorithms do not consider the time and frequency domain features fully, and have the shortcoming of small key space, a discrete orthonormal Stockwell transform(DOST) based color image encoding and decoding technique is proposed. Firstly, image is divided into RGB three channels, each channel is processed by DOST independently.Then, each channel is processed by the first level DWT, so that each channel is decomposed into four subbands.Furthermore, DWT is used to decompose each subband.Lastly, the singular value is processed with multiplication operation and the new singular value is used to reconstruct all subbands. The number of bands used in DOST, parameters used with singular values and arrangement of DWT subbands can be selected as encoding keys, so it is very hard to get the correct key. Experiments results show that the proposal has better encryption and security performance than the other algorithms.