Most of the existing image encryption schemes with the substitution-diffusion 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 pseudo-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.
