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Nowadays, preventing data transmission via networks from unauthorized access has become crucial. In this work, we introduce a new enhanced Crow Search Algorithm (CSA), named NECSA, for solving the search problem. Then, we propose a steganographic approach called Steganographic NECSA (SNECSA). It is based on NECSA for obtaining optimal positions and the Least Significant Bit (LSB) method for concealing secret data in these positions. For gray-scale images, SNECSA is applied with 4-LSB. For colored images, SNECSA is applied in two versions. The first one uses 3–3–2 LSB, while the other uses 3–3–2 LSB and permutations on each secret byte, obtaining six patterns and choosing the fittest pattern to embed. The practical results show that the proposed approach outperforms other previous approaches with respect to peak signal to noise ratio, bit error rate, and number of pixel change, where the average peak signal to noise ratios achieved by the proposed approach are approximately 76.25 dB, 73.47 dB, and 71 dB in gray-scale images, and 83.76 dB, 80.9 dB, and 78.7 dB in color images on the tested data set. Additionally, the suggested approach shows outstanding resistance to stego-attacks such as salt and paper noise and regular and singular analysis. [ABSTRACT FROM AUTHOR]

The security of many public key cryptosystems that are used today depends on the difficulty of factoring an integer into its prime factors. Although there is a polynomial time quantum-based algorithm for integer factorization, there is no polynomial time algorithm on a classical computer. In this paper, we study how to improve the wheel factoring method using two approaches. The first approach is introducing two sequential modifications on the wheel factoring method. The second approach is parallelizing the modified algorithms on a parallel system. The experimental studies on composite integers n that are a product of two primes of equal size show the following results. (1) The percentages of improvements for the two modified sequential methods compared to the wheel factoring method are almost 47 % and 90 % . (2) The percentage of improvement for the two proposed parallel methods compared to the two modified sequential algorithms is 90 % on the average. (3) The maximum speedup achieved by the best parallel proposed algorithm using 24 threads is almost 336 times the wheel factoring method. [ABSTRACT FROM AUTHOR]

We present a new version of Advanced Encryption Standard (AES), called DNAES, based on deoxyribonucleic acid (DNA) sequences with silent mutations. We present how to encode and decode data in a DNA sequence and how to perform the different steps of AES. The proposed cipher has the following features: (1) it can be applied to any type of data (e.g., text, videos, images); (2) it has the same security level as AES; (3) it can be implemented in a biological environment or on DNA computers; (4) because the ciphertext generated by DNAES does not actually change the amino acid sequence of the protein, side effects are avoided; and (5) besides encryption, the proposed cipher can be used to hide data in a DNA sequence. [ABSTRACT FROM AUTHOR]

A graphics processing unit (GPU) has been widely used to accelerate discrete optimization problems. In this paper, we introduce a novel hybrid parallel algorithm to generate a shortest addition chain for a positive integer e. The main idea of the proposed algorithm is to divide the search tree into a sequence of three subtrees: top, middle, and bottom. The top subtree works using a branch and bound depth first strategy. The middle subtree works using a branch and bound breadth first strategy, while the bottom subtree works using a parallel (GPU) branch and bound depth first strategy. Our experimental results show that, compared to the fastest sequential algorithm for generating a shortest addition chain, we improve the generation by about 70% using one GPU (NVIDIA GeForce GTX 770). For generating all shortest addition chains, the percentage of the improvement is about 50%. [ABSTRACT FROM AUTHOR]

The aim of this paper is to generalize some results on addition chains to addition-multiplication chains. The paper concerns with generating shortest addition-multiplication chains. It first presents two methods for generating short addition-multiplication chains. Second, it presents an algorithm for generating a shortest addition-multiplication chain. Then it proposes three main improvements for generating a shortest addition-multiplication chain. The practical results show that the proposed improvements reduce, on the average, the running time and storage of the algorithm by about 95% and 35% respectively for data range 12 - 20 bits. Similar practical results are obtained for generating all shortest addition-multiplication chains. Finally, the paper discusses how to apply the algorithm to obtain some results that have been uncovered previously. [ABSTRACT FROM AUTHOR]