Most of the existing image encryption schemes with the substitutlon-chltuslon structure are not secure and efficient. In this letter, a chaos-based pseudo-random bit generator with good statistical properties is proposed, where a simple post-processing by compressing is employed. A new adaptive image encryption scheme with the substitution-diffusion architecture is designed using the new pseu- do-random bit generator. In the scheme, the session key for the pseudo-random bit generator is dependent on the content of the image which ensures that the scheme can effectively resist knownplaintext and chosen-plaintext attacks. Theoretical analysis and computer simulation indicate that the proposed algorithm is efficient and highly secure.
A new algorithm for a novel hash function, based on chaotic tent map with changeable parameter, is proposed and analyzed. The one dimensional and piecewise tent map with changeable parameters decided by the position index of blocked messages is chosen, and blocked massages translated into ASCII code values are employed as the iteration time of the chaotic tent map. The final 128-bit hash value is generated by logical XOR operation on intermediate hash values. Theoretical analysis and computer simulation indicate that the proposed algorithm can satisfy the performance requirements of hash function.
