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The use of cryptography, or the art of secret writing, to secure information exchanged via an open medium is an ancient technique, but its significance in the modern world has greatly expanded. It has become necessary to search for ever-better cryptographic primitives that offer a level of security while limiting the time needed to encrypt and decode the data as eavesdroppers' computational power has increased. Each letter in the message is swapped out for a different letter using a substitution cipher that follows a predetermined mapping. A, B, and C are shown as an image of two alphabets with a mapping between them: D, E, and F. the Caesar cipher is an easy illustration of a substitution cipher. When more than one independent layer of encryption is used, it is known as double encryption and it serves as a safeguard against the compromising of any one layer. The dangers associated with encrypting data are reduced by using two levels of encryption. Concurrent Error Detection (CED) for cryptographic chips also offers a huge potential for detecting (intentional) fault injection attacks when errors are injected into a cryptographic chip to break the key. For a family of symmetric block ciphers whose round functions are involutions, we present in this study a temporal redundancy based CED approach that is low cost, low latency, and effective. Nearly little more time is required for this CED approach to identify both ongoing and passing errors. F(F(x))=x indicates that a function F is an involution. [ABSTRACT FROM AUTHOR]

With the Internet of Things (IoT), mobile healthcare applications can now offer a variety of dimensionalities and online services. Disease Prediction Systems (DPS) increase the speed and accuracy of diagnosis, improving the quality of healthcare services. However, privacy is garnering an increasing amount of attention these days, especially concerning personal healthcare data, which are sensitive. There are a variety of prevailing privacy preservation techniques for disease prediction that are rendered. Nonetheless, there is a chance of medical users being affected by numerous disparate diseases. Therefore, it is vital to consider multi-label instances, which might decrease the accuracy. Thus, this paper proposes an efficient privacy-preserving (PP) scheme for patient healthcare data collected from IoT devices aimed at disease prediction in the modern Health Care System (HCS). The proposed system utilizes the Log of Round value-based Elliptic Curve Cryptography (LR-ECC) to enhance the security level during data transfer after the initial authentication phase. The authorized healthcare staff can securely download the patient data on the hospital side. Utilizing the Herding Genetic Algorithm-based Deep Learning Neural Network (EHGA-DLNN) can test these data with the trained system to predict the diseases. The experimental results demonstrate that the proposed approach improves prediction accuracy, privacy, and security compared to the existing methods. [ABSTRACT FROM AUTHOR]

This paper presents state-of-art cryptanalysis studies on attacks of the substitution and transposition ciphers using various metaheuristic algorithms. Traditional cryptanalysis methods employ an exhaustive search, which is computationally expensive. Therefore, metaheuristics have attracted the interest of researchers in the cryptanalysis field. Metaheuristic algorithms are known for improving the search for the optimum solution and include Genetic Algorithm, Simulated Annealing, Tabu Search, Particle Swarm Optimization, Differential Evolution, Ant Colony, the Artificial Bee Colony, Cuckoo Search, and Firefly algorithms. The most important part of these various applications is deciding the fitness function to guide the search. This review presents how these algorithms have been implemented for cryptanalysis purposes. The paper highlights the results and findings of the studies and determines the gaps in the literature. [ABSTRACT FROM AUTHOR]

In this paper I describe an activity based on a 1903 Sherlock Holmes murder mystery, in which a substitution cipher is used to encrypt secret messages. The story provides a fun and interesting way to talk about frequency analysis, and can be used as a segue into mathematical constructs such as modular arithmetic and computation. The activity is accessible to ages twelve and above, and has been successfully used in mathematics outreach and popularization efforts as well as in general education and mathematics courses. [ABSTRACT FROM AUTHOR]

Due to the rapid development of distributed computing systems, the use of local networks, and the huge expansion of the Internet, the process of maintaining the confidentiality of information becomes important and necessary. Encryption is one of the most important ways to keep information confidential and to prevent unauthorized people from disclosing this information. Many cryptographic algorithms have appeared in different ways and methods. But most of these algorithms have been devoted for encrypting texts in the English language. Because of the increasing important and sensitive information exchange in the Arabic language by users on the Internet, an urgent need has appeared to build dedicated encryption systems for the Arabic language. The aim of this research is to provide a proposed encryption method that uses the idea of combining the methods of transposition and substitution cipher for the purpose of Arabic texts confidentiality. This research depends on using diacritics in the Arabic language to perform the process of substitution cipher. The efficiency of the proposed method has been tested on different texts; the method provides high speed execution, the length of the encrypted texts is almost close to the clear text length, and the confidentiality of the resulting encrypted texts is high.

With the Internet of Things (IoT), mobile healthcare applications can now offer a variety of dimensionalities and online services. Disease Prediction Systems (DPS) increase the speed and accuracy of diagnosis, improving the quality of healthcare services. However, privacy is garnering an increasing amount of attention these days, especially concerning personal healthcare data, which are sensitive. There are a variety of prevailing privacy preservation techniques for disease prediction that are rendered. Nonetheless, there is a chance of medical users being affected by numerous disparate diseases. Therefore, it is vital to consider multi-label instances, which might decrease the accuracy. Thus, this paper proposes an efficient privacy-preserving (PP) scheme for patient healthcare data collected from IoT devices aimed at disease prediction in the modern Health Care System (HCS). The proposed system utilizes the Log of Round value-based Elliptic Curve Cryptography (LR-ECC) to enhance the security level during data transfer after the initial authentication phase. The authorized healthcare staff can securely download the patient data on the hospital side. Utilizing the Herding Genetic Algorithm-based Deep Learning Neural Network (EHGA-DLNN) can test these data with the trained system to predict the diseases. The experimental results demonstrate that the proposed approach improves prediction accuracy, privacy, and security compared to the existing methods.

This study proposes the hybrid substitution cryptography method followed by chaotic methods to improve the security of digital image transactions on the internet. The substitution method used is a hybrid of the modification of the Vigenère and Beaufort cipher algorithm. To do a hybrid, two random keys are used. The first random key is a matrix with 8-bits integer values, while the second random key is a matrix that contains binary values. The modulus operation is used in the main process of substitution methods. In this study, 24-bits true-color images were used as a dataset for the testing experiment. Measurement of encryption quality is measured by Entropy, MSE, PSNR, SSIM, UACI, and NPCR, whereas tic toc functions for measuring the computational time needed. To ensure the decryption process runs perfectly, measuring instruments such as SSIM, MSE, and PSNR are used to compare the decrypted image with the original image, the tic toc function is also used to measure computing performance. Based on the results of testing the quality of image encryption proved to have excellent results where the entropy value is very close to 8, the ideal NPCR and UACI values, as well as excellent visual values based on MSE, PSNR, and SSIM measurements. The image can also be decrypted perfectly with relatively fast computing time in the encryption and decryption process. [ABSTRACT FROM AUTHOR]

Copyright of Baghdad Science Journal is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A Vigenère cipher applies a single short key repeatedly to encrypt a plaintext. If a cryptanalyst correctly finds out the key length, the ciphertext can be divided into multiple instances of shift cipher and be broken by frequency analysis. To determine the key length, the twist algorithm, an alternate method to the standard Kasiski and Friedman tests, was recently proposed. In this article, we propose the twist+ algorithm, an improved twist algorithm, which can estimate the key length more accurately than the original twist algorithm. [ABSTRACT FROM AUTHOR]

• The first main idea and it is not used before, is to use homographic function. • The second original idea is to work in finite field Z/257Z, 257 is prime number. • Our cryptosystem based on homographic function is a kind of substitution cipher. In this paper, we adapt a homographic function to encrypt digital images, which takes into account the value of the pixel as well as its position in the image. The homographic function is a function represented as a quotient of two affine functions in a switching field K; it is represented by four different coefficients of zeros, which must verify certain conditions. One take the field K equal Z/257Z switching field (257 is a prime number), (all its non-zero elements are invertible, we take into account the following condition if we have 0 as the pixel value we put 256), 256 is the inverse of 256 in Z/257Z. We will show that this a homophonic substitution, which can represent the confusion part in a modern cryptographic system. We strengthened this proposal by a diffusion method and, we have used the Hénon attractor of is 2-dimensional; each pixel will be permuted to another position of the encrypted image. We managed to build a cryptosystem who passed all the statistic tests, and that has a secret key of 253 bits in length. [ABSTRACT FROM AUTHOR]

Copyright of AL-yarmouk Journall is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, we propose new method for automated cryptanalysis of substitution cryptosystem using Hill climbing algorithm. New heuristic function is proposed in order to drastically improve overall fitness of the standard Hill climbing algorithm. Several fitness functions have been tested and we try to detremine which of them perform better in specific situations using our suggested time-dependent measure goodness. We conclude which of those functions should be used in case we are dealing with short or long texts. [ABSTRACT FROM AUTHOR]

Copyright of Journal of University of Anbar for Pure Science is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Caesar cipher is a mono alphabetic cipher. It is also a type of substitution cipher in which each letter in the plaintext is 'shifted' a certain number of places down the alphabet. However, Caesar cipher method did not last long because of its simplicity and lack of communication security. Therefore, we believe that strengthen the key mechanism should increase its complexity against the various cryptanalysis attacks. This paper proposes an enhanced Caesar cipher method through adopting two private keys that are tied to the character positions (i.e. odd and even) for encryption and/or decryption. The two private keys are mapped into one public key to be transferred to the recipient. At the end, the results show that the new cryptosystem is inevitable to cryptanalysis attack. And the cipher text is reduced in size and thus, memory space. The public key generation process is proven to be a one-way function utilizing binary matrices that are generated and shared between the two communicating parties. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Every encryption technique is based on any one of two facts-substitution or transposition. Sometimes the combination of both techniques is used. Substitution technique is based on replacement of given plaintext letters by other letters or symbols to get the ciphertext. The basic concept behind this paper is to improve the strength of Hill cipher, 'a multiple-letter substitution cipher' against known plaintext attack. This paper presents a modified approach which is an enhancement over traditional Hill cipher by using symmetric matrix of plaintext letters. [ABSTRACT FROM AUTHOR]

We study the historical evidences of early cryptography in Ancient World. The constructions and using practices of the most important protocryptographic techniques are analyzed. Basing on these facts, we offer our versions about functions of the pre-scientific ciphers in Ancient World. We also conclude about their properties and ways of improvement.

We investigate the use of Markov Chain Monte Carlo (MCMC) methods to attack classical ciphers. MCMC has previously been used to break simple substitution ciphers. Here, we extend this approach to transposition ciphers and to substitution-plus-transposition ciphers. Our algorithms run quickly and perform fairly well even for key lengths as high as 40. [ABSTRACT FROM AUTHOR]

We introduce a method for solving substitution ciphers using low-order letter n-gram models. This method enforces global constraints using integer programming, and it guarantees that no decipherment key is overlooked. We carry out extensive empirical experiments showing how decipherment accuracy varies as a function of cipher length and n-gram order. We also make an empirical investigation of Shannon's [12] theory of uncertainty in decipherment. [ABSTRACT FROM AUTHOR]