Protecting patient privacy and medical records is a legal requirement. Traditional encryption methods fall short of handling the large volume of medical image data and their peculiar statistical properties. In this paper, we propose a generic medical image encryption framework based on a novel arrangement of two very efficient constructs, dynamic substitution boxes (S-boxes) and chaotic maps. The arrangement of S-box substitution before and after chaotic substitution is shown to successfully resist chosen plaintext and chosen ciphertext attacks. Special precautions are taken to fend off the reset attack against pseudorandom number generators. We show how to implement the generic framework using any key-dependent dynamic Sbox construction method and any chaotic map. Experimental results show that the proposed framework successfully passes all security tests regardless of the chaotic map used for implementation. Based on speed analysis, we recommend the use of the classical Baker map or Henon map to achieve encryption throughput approaching 90 MB/s on a modern PC without hardware acceleration. INDEX TERMS bijective substitution box, chaotic map, image encryption.

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ABSTRACT

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.

The performance of underwater sensor networks (UWSNs) is greatly limited by the low bandwidth and high propagation delay of acoustic communications. Deploying multiple surface-level radio-capable gateways can enhance UWSN performance metrics, reducing end-to-end delays and distributing traffic loads for energy reduction. In this paper, we study the problem of gateway placement for maximizing the cost-benefit of this UWSN architecture. We develop a mixed integer programming (MIP) gateway deployment optimization framework. We analyze the tradeoff between the number of surface gateways and the expected delay and energy consumption of the surface gateway architecture in the optimal case. We used an MIP solver to solve the developed optimization problem and integrated the optimal results to serve as an input for our simulations to evaluate the benefits of surface gateway optimization framework. We investigated the effect of acoustic channel capacity and the underwater sensor node deployment pattern on our solution. Our results show the significant advantages of surface gateway optimization and provide useful guidelines for real network deployment.

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