Partial Encryption of Color Image Using Quaternion Discrete Cosine Transform

In this paper, the quaternion discrete Cosine transform (QDCT) is applied to the color image encryption technology, and partial encryption technique of color image based on QDCT is proposed. Obtained the QDCT spectrum of color image by QDCT, the real and imaginary parts of QDCT coefficients are quantized and encoded with the color image quantization coefficient table and QDCT coefficients encoding method, and part of low and high frequency coefficients are encrypted in the encoding process. Simulation results and security performance analysis shows that the proposed scheme can obtain the effect of secure image encryption, reduce the amount of encryption data and transmission data, and well distribute the pixels of the original image when only part of the data are encrypted. What’s more, the proposed scheme can decrypt and recover the original image with high quality. Due to the large key space, the proposed scheme can resist exhaustive attacks.