Breaking a novel image encryption scheme based on improved hyperchaotic sequences

Recently, a novel image encryption scheme based on improved hyperchaotic sequences was proposed. A pseudorandom number sequence, generated by a hyper-chaos system, is used to determine two involved encryption functions, bitwise exclusive or (XOR) operation and modulo addition. It was reported that the scheme can be broken with some pairs of chosen plain-images and the corresponding cipher-images. This paper re-evaluates security of the encryption scheme and finds that the encryption scheme can be broken with only one known plain-image. The performance of the known-plaintext attack, in terms of success probability and computation load, become even much better when two known plain-images are available. In addition, security defects on insensitivity of encryption result with respect to changes of secret key and plain-image, are reported also.