To improve the safety of information encryption, based on an improper fractional-order laser chaos, a digital image encryption algorithm is proposed. The key space is formed by initial state variables, parameters and orders of the system. Every pixel value is included in secret key, so as to improve anti-attack capability of the algorithm. Lena gray image and Couple color image are encrypted in numerical simulation. Theoretical analysis and simulation results show that this algorithm with a sufficiently large key space not only can perfectly resist the ciphertext attack and differential attack, but also is excellent against chosen plaintext attack and statistical attack, which can be used in secure communication of multimedia data.
