In order to improve the security of color image encryption, the secret key of the encryption algorithm must have a strong correlation with the original image, but it should not reveal its information. It is difficult to meet this requirement using the current secret key generation algorithm. Thus, we propose a new secret key generation algorithm based on operations on the DC and AC values in YUV space. These two values are extracted from the process discrete cosine transformation of the data after image color space transformation. By combining the new secret key and the given secret key together as the initial values of chaotic maps, we can encrypt a color image in YUV and RGB space through multi-chaotic maps. Our experimental results indicate that this secret key algorithm is highly effective and the encryption method has a relatively high security.
Zhou, S., Wei, Z., Wang, B., Zheng, X., Zhou, C., & Zhang, Q. (2016). Encryption method based on a new secret key algorithm for color images. AEU - International Journal of Electronics and Communications, 70(1), 1–7. https://doi.org/10.1016/j.aeue.2015.08.010