Image encryption schemes can be vulnerable to a variety of cryptanalysis attacks. The use of key-dependent dynamic S-boxes has been shown to improve security. Threats of chosen-plaintext and chosen-ciphertext attacks still linger. In this paper, we present an efficient algorithm for constructing secure dynamic S-boxes derived from Henon map. We use the proposed dynamic S-box to construct an image encryption scheme that includes a novel combination of security features to resist chosen-plaintext and chosen-ciphertext attacks. Namely, a hash verification step at the end of the decryption procedure effectively thwarts chosen-ciphertext attacks. The hash also serves as an image dependent initialization for the keystream, which together with using an image dependent S-box resist known-plaintext attacks. Furthermore, encryption keys are protected against cryptanalysis using elliptic curve cryptography (ECC).Therefore, the recovery of secret keys is as hard as the elliptic curve discrete logarithm problem even in the unlikely case of the recovery of the temporary S-box or keystream. Our evaluation of the proposed image encryption scheme reveals that it achieves a higher security standard than existing techniques. Moreover, the proposed scheme is computationally efficient with encryption throughput approaching 60 MB/s. INDEX TERMS chaotic map, elliptic curve cryptography, image encryption, substitution box.

Most of the computational time in many chaotic image encryption schemes is spent generating the required chaotic sequences. Since chaotic systems are defined by recurrence relations, they are often generated sequentially. In this paper, we propose a chaotic image encryption scheme which enables pixellevel parallelism to boost the computational speed of generating chaotic sequences. We use a group defined over elliptic curve (EC) points and the addition operator to generate a discrete chaotic sequence and use it to construct an image encryption scheme. The proposed scheme is designed such that encryption and decryption operations are highly parallelizable to take advantage of readily available parallel processing platforms such as GPU acceleration, DSPs and multi-core CPUs. Complexity analysis indicates that the proposed scheme is more efficient than existing EC-based image encryption schemes. Practical experiments on a quad-core CPU show that the proposed scheme can achieve a speedup of 3.93, confirming its superior parallelization efficiency in comparison with existing parallel image encryption schemes. We also provide detailed analysis of the immunity of the proposed scheme to all common cryptanalysis attacks. Results reveal that the proposed technique shows promising performance in terms of security and efficiency.INDEX TERMS image encryption, parallel processing, elliptic curve, chaotic maps.

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