An asymmetric color image encryption method by using deduced gyrator transform

- A new asymmetric color image encryption method deduced from the GT is proposed.
- The inverse operation of the GT is not required in the decryption process.
- A gray ciphertext can bewilder unauthorized users.
- The encrypted result is real-valued.

An encryption algorithm is proposed by using the properties of deduced gyrator transform (GT). After being transformed by the GT algorithm and multiplied by a phase distribution p*, the spectrum modulus of the input image is considered to be the encrypted image by further performing Fourier transformation. To resist the attack from iterative phase retrieval, the red, green and blue components of the input image is modulated by a random phase mask and then combined using convolution. The encryption result is real-valued, which is convenient for display, transmission and storage. In the decryption process, the three original color components can be recovered with decryption keys which are different from the encryption keys. An optoelectronic hybrid system for the encryption process is also presented. Computer simulations are presented to demonstrate its performance, and the security of the proposed system is analyzed as well.