Substitution Cipher Research Articles

Atbah-Type Ciphers in the Christian Orient and Numerical Rules in the Construction of Christian Substitution Ciphers

This article presents Christian ciphers (counterparts of the well-known Hebrew atbah cipher) used in main languages and scripts of the Christan Orient: in Greek, Coptic, and Syriac, in Late Antiquity and the Middle Ages. The article also describes other alphabetic substitution ciphers used in these languages and highlights numerical rules in their construction.

ON PERFECT IMITATION RESISTANT CIPHERS OF SUBSTITUTION WITH UNBOUNDED KEY

Constructions of perfect imitation resistant ciphers are investigated in the work. It is well known that Vernam cipher with equiprobable gamma is a perfect cipher but it is not imitation resistant. It is because in Vernam cipher equipotent alphabets for plaintexts and ciphertexts are used. On the basis of A.Yu. Zubov's mathematical model of substitution cipher with unbounded key a model of perfect and imitation resistant cipher is constructed. At that reference cypher of the given model is perfect and reaches lower boundaries for success probability of imitation and substitution of communication.

Modified Caesar Cipher for Better Security Enhancement

is the process of scrambling a message so that only the intended recipient can read it. With the fast progression of digital data exchange in electronic way, Information Security is becoming much more important in data storage and transmission. Caesar cipher is a mono alphabetic cipher. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter. In this paper, author modified the traditional Caesar cipher and fixed the key size as one. Another thing alphabet index is checked if the alphabet index is even then increase the value by one else alphabet index is odd decrease the key value by one. Encryption and scrambling of the letters in the Cipher Text.

Simple substitution distance and metamorphic detection

To evade signature-based detection, metamorphic viruses transform their code before each new infection. Software similarity measures are a potentially useful means of detecting such malware. We can compare a given file to a known sample of metamorphic malware and compute their similarity—if they are sufficiently similar, we classify the file as malware of the same family. In this paper, we analyze an opcode-based software similarity measure inspired by simple substitution cipher cryptanalysis. We show that the technique provides a useful means of classifying metamorphic malware.

Efficient Cryptanalysis of Homophonic Substitution Ciphers

Substitution ciphers are among the earliest methods of encryption. Examples of classic substitution ciphers include the well-known simple substitution and the less well-known homophonic substitution. Simple substitution ciphers are indeed simple, both in terms of their use and their cryptanalysis. Homophonic substitutions—in which a plaintext symbol can map to more than one ciphertext symbol—are also easy to use, but far more challenging to break. Even with modern computing technology, homophonic substitutions can present a significant cryptanalytic challenge. This article focuses on the design and implementation of an efficient algorithm to break homophonic substitution ciphers. The authors employ a nested hill climb approach that generalizes the fastest known attack on simple substitution ciphers. They test their algorithm on a wide variety of homophonic substitutions and provide success rates as a function of both the ciphertext alphabet size and ciphertext length. Finally, they apply their technique to the “Zodiac 340” cipher, which is an unsolved message created by the infamous Zodiac killer.

Secured Wireless Data Communication

Security of data in army stations is an important issue. In early systems, at the time of information transmission between two army stations, it can be hacked by terrorists, spies and enemies. Cryptography is a very important system employed for this purpose. There are various types of algorithms available for encryption and decryption of data and new algorithms are evolving. Polyalphabetic substitution cipher is a strong algorithm used for security of data in army stations. In this paper, various techniques of security of data and one the algorithm using polyalphabetic substitution cipher are discussed.

Novel cipher technique using substitution method

Cryptography plays a very vital role in the field of Network Security. It is a complex and mathematically challenging field of study. Always there exists a need for confidentiality and integrity of all information being transmitted on the network that is very important for certain communicating parties. The data being transmitted needs to be kept secure and out of reach for unauthorized access. In this paper, we purpose a new symmetric substitution cipher technique using a mechanism on vowel, consonants of English language and numeric digits, which exploits the disadvantages of the symmetric substitution techniques previously known to us. Also certain new aspects of encryption and decryption have been explored.

A Technique for Secure Communication Using Message Dependent Steganography

In this paper we present a technique for secure communication between two parties Alice and Bob. We use both cryptography and steganography. We take image as the carrier to use steganography. By using our own substitution cipher called two square reverse we encrypt the secret information. Then the cipher text of the secret information is embedded into the carrier image in LSB (least significant bit) minus one position of some selected bytes. The byte selection is done depending on the bit pattern of the secret information. Thus the embedding locations are dependent on the secret message. So the intruder will face difficulties to locate the bits. After embedding the resultant image will be sent to the receiver, the receiver will apply the reverse operation what the sender has done and get the secret information.

A Simple Algebraic Model based Polyalphabetic Substitution Cipher

ABSTRACT Cryptography is considered to be a disciple of science of achieving security by converting sensitive information to an un-interpretable form such that it cannot be interpreted by anyone except the transmitter and intended recipient. An innumerable set of cryptographic schemes persist in which each of it has its own affirmative and feeble characteristics. In this paper we have we have developed a traditional or character oriented Polyalphabetic cipher by using a simple algebraic equation. In this we made use of iteration process and introduced a key K 0 obtained by permuting the elements of a given key seed value. This key strengthens the cipher and it does not allow the cipher to be broken by the known plain text attack. The cryptanalysis performed clearly indicates that the cipher is a strong one. . Keywords Polyalphabetic substitution, variable length key stream, bit-ratio test, frequency test. 1. INTRODUCTION Cryptography is considered to be a collection of tools and techniques related to components of information security such as confidentiality, authenticity, integrity, non-repudiation [1]. Cryptography refers to the science of securing data by changing the data into non-interpretable form, cryptanalysis is the science of analyzing and breaking secure communication. Cryptanalyst or attacker is a person who performs cryptanalysis [2]. Cryptology is a combination of both cryptography and cryptanalysis. A no of cryptanalytic attacks can be found wherein cipher text only, known plaintext, chosen plaintext, chosen cipher text, adaptive chosen plaintext, brute force attack, key guessing attack etc are to name a few [3]. In this paper we propose a simple algebraic model based Polyalphabetic substitution cipher wherein the plain text is converted to cipher text by the use of a key-seed value from which variable length key stream is generated producing different cipher text with every run time for similar entered plain text. In section 2 we have presented the basic terminologies. Section 3 depicts the proposed algorithm both for encryption and decryption. In section 4 we have presented the experimental results. Testing and analysis is given in section 5 comprising of frequency distribution test, bit-ratio test, encryption and decryption time comparison and comparison of plain text size with cipher file size. On the basis of testing and analysis performed conclusions are drawn in section 6.

Decrypting classical cipher text using Markov chain Monte Carlo

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.

Decipherment of Substitution Cipher using Enhanced Probability Distribution

theoretic approach for decipherment problems is the recent trend in cryptanalysis. The behavioral transformation of message units is addressed upto certain extent in the encryption process. However the amount of confusion and diffusion in terms of statistical distribution parameters between message and cipher text is a point of interest for cryptanalyst. In the present work we addressed this issue with the help of enhanced probability distribution function. The basic units of any message text are observed to be heuristic in nature depending on the sample. Averaging function is adopted while evaluating the enhanced probabilities of message units. The retrieved efficiency of cipher text only attack on samples of English, Hindi Telugu, Kannada is presented in this paper.

BioCryptography

Biology has been a rich source of inspiration for computer security professionals. The central dogma of biology contains two ciphers with three one-to-many mappings: (1), substitution cipher and (2) intronization cipher. These mappings have a certain degree of one-way property because inverse mapping can be extremely difficult. Therefore, I prefer to call them biological one-way functions. The security of the substitution cipher can be improved by representing information with DNA, RNA, and protein alphabets and by using modified genetic code. The intronization cipher can be secured with pseudo-random sequence. The randomized intronization technique is tested as a one-way hashing mechanism to protect fingerprint templates.

A Comparison between Memetic algorithm and Genetic algorithm for the cryptanalysis of Simplified Data Encryption Standard algorithm

Genetic algorithms are a population-based Meta heuristics. They have been successfully applied to many optimization problems. However, premature convergence is an inherent characteristic of such classical genetic algorithms that makes them incapable of searching numerous solutions of the problem domain. A memetic algorithm is an extension of the traditional genetic algorithm. It uses a local search technique to reduce the likelihood of the premature convergence. The cryptanalysis of simplified data encryption standard can be formulated as NP-Hard combinatorial problem. In this paper, a comparison between memetic algorithm and genetic algorithm were made in order to investigate the performance for the cryptanalysis on simplified data encryption standard problems(SDES). The methods were tested and various experimental results show that memetic algorithm performs better than the genetic algorithms for such type of NP-Hard combinatorial problem. This paper represents our first effort toward efficient memetic algorithm for the cryptanalysis of SDES. This paper proposes the cryptanalysis of simplified encryption standard algorithm using memetic and genetic algorithm. The cryptanalysis of simplified data encryption standard can be formulated as NP-Hard combinatorial problem. Solving such problems requires effort (e.g., time and/or memory requirement) which increases with the size of the problem. Techniques for solving combinatorial problems fall into two broad groups - traditional optimization techniques (exact algorithms) and non traditional optimization techniques (approximate algorithms). A traditional optimization technique guarantees that the optimal solution to the problem will be found. The traditional optimization techniques like branch and bound, simplex method, brute force search algorithm etc methodology is very inefficient for solving combinatorial problem because of their prohibitive complexity (time and memory requirement). Non traditional optimization techniques are employed in an attempt to find an adequate solution to the problem. A non traditional optimization technique - memetic algorithm, genetic algorithm, simulated annealing and tabu search were developed to provide a robust and efficient methodology for cryptanalysis. The aim of these techniques to find sufficient solution efficiently with the characteristics of the problem, instead of the global optimum solution, and thus it also provides attractive alternative for the large scale applications. These nontraditional optimization techniques demonstrate good potential when applied in the field of cryptanalysis and few relevant studies have been recently reported. In 1993 Spillman (16) for the first time presented a genetic algorithm approach for the cryptanalysis of substitution cipher using genetic algorithm. He has explored the possibility of random type search to discover the key (or key space) for a simple substitution cipher. In the same year Mathew (12) used an order based genetic algorithm for cryptanalysis of a transposition cipher. In 1993, Spillman (17), also successfully applied a genetic algorithm approach for the cryptanalysts of a knapsack cipher. It is based on the application of a directed random search algorithm called a genetic algorithm. It is shown that such a algorithm could be used to easily compromise even high density knapsack ciphers. In 1997 Kolodziejczyk (11) presented the application of genetic algorithm in cryptanalysis of knapsack cipher .In 1999 Yaseen (18) presented a genetic algorithm for the cryptanalysis of Chor-Rivest knapsack public key cryptosystem.

A first study of improving transposition cryptosystem

Transposition ciphers are stronger than simple substitution ciphers. However, if the key is short and the message is long, then various cryptanalysis techniques can be applied to break such ciphers. By adding 8 bits (one byte) for each byte using a function and a binary tree, we can make this cipher protected. Using an inorder tour on binary tree can diffuse the eight bits and eight bits of a byte of plaintext. This can highly protect the cipher however, if the key management processes are not secure the strongest ciphers can easily broken.

Cracking Hill Ciphers with Goodness-of-Fit Statistics

The Hill cipher, also known as matrix encryption, is a polygraphic substitution cipher, developed by the mathematician Lester S. Hill in 1929. While various attacks had been known on the Hill cipher, the ciphertext-only attack without assumptions about the encryption matrix or probable plaintext words was introduced only recently by Bauer and Millward. They obtained high efficiency of attack by recovering the decryption matrix row by row rather than all rows at once. In this paper, we extend their ciphertext-only attack in two ways. First, we present a better scoring system for cryptanalysis based on the goodness-of-fit statistics. Specifically, we reduce the average number of candidate rows from 24.83 to 7.00 for 3 × 3 matrix and from 4027.78 to 1220.38 for 4 × 4 matrix. Second, we show how to apply our attacks to the Hill cipher without knowing the numeric equivalents of the letters of the plaintexts.

Attacking Letter Substitution Ciphers with Integer Programming

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.

An Approach in Improving Transposition Cipher System

Transposition ciphers are stronger than simple substitution ciphers. However, if the key is short and the message is long, then various cryptanalysis techniques can be applied to break such ciphers. By adding 8 bits (one byte) for each byte using a function and another mathematical function to position the bits in a binary tree and using its in-order tour, this cipher can be made protected. Using an in-order tour of binary tree can diffuse the eight bits (includes 7 bits produced by the function and 1 random bit) and eight bits of the plaintext. This can highly protect the cipher. However, if the key management processes are not secured the strongest ciphers can easily be broken.

Encrypted objects and decryption processes: problem-solving with functions in a learning environment based on cryptography

This paper introduces an applied problem-solving task, set in the context of cryptography and embedded in a network of computer-based tools. This designed learning environment engaged students in a series of collaborative problem-solving activities intended to introduce the topic of functions through a set of linked representations. In a classroom-based study, students were asked to imagine themselves as cryptanalysts, and to collaborate with the other members of their small group on a series of increasingly difficult problem-solving tasks over several sessions. These tasks involved decrypting text messages that had been encrypted using polynomial functions as substitution ciphers. Drawing on the distinction between viewing functions as processes and as objects, the paper presents a detailed analysis of two groups’ developing fluency with regard to these tasks, and of the aspects of the function concept underlying their problem-solving approaches. Results of this study indicated that different levels of expertise with regard to the task environment reflected and required different aspects of functions, and thus represented distinct opportunities to engage those different aspects of the function concept.

Application of Polyalphabetic Substitution Cipher using Genetic Algorithm

Several Genetic Algorithms have been developed for applications of cryptography problem; the primary distinction among all of them being the G.A. used for decryption problem and obtains the plain text. In this paper a new approach is proposed using Genetic Algorithm with cryptography. G.A. is used to obtain a best secret key in polyalphabetic substitution cipher. This key will be used then for encryption and decryption with a high level of security. The program is written in Matlab language (6.5).

A method for distorting the frequency of character occurrence in the simple substitution cipher

A method for distorting the frequency of character occurrence in the simple substitution cipher