Chaos-based image hybrid encryption algorithm using key stretching and hash feedback

The paper proposes a chaos-based image hybrid stream and block encryption algorithm, a key stretching method is implemented to further enhance its security. The random time span sequence and salt sequences are generated by the Logistic-Sine map. The key stretching method repeatedly feeds salt and current intermediate hash value of state variables back into the next round message for hash function simultaneously, and the state variables are extracted from Sprott C system through time span sequence, the aim of redundant iterations of Sprott C system is to resist side channel attack. After multiple iteration loops, the key stream is generated by Sprott C system to encrypt pixel blocks of the pre-encoded image. Experimental results and security analysis demonstrated the scheme's effectiveness and resistance to all kinds of known attacks.