CRYPTANALYSIS OF TYPEX

Rotor cipher machines played a large role in World War II: Germany used Enigma; America created Sigaba; Britain developed Typex. The breaking of Enigma by Polish and (later) British cryptanalysts had a huge impact on the war. Despite be- ing based on the commercial version of the Enigma, there is no documented successful attack on Typex during its time in service. This project covers the Typex machine. We consider the development of Typex, we discuss how Typex works, and we present and analyze two distinct cryptanalytic attacks on the cipher. The first attack assumes the rotor wirings are known and uses Turing’s crib attack–originally developed for Enigma–to recover the settings of the stepping rotors. It then performs a hill-climb to recover the static rotor settings. The second attack assumes that the rotor wirings are unknown. This attack uses a nested hill-climb to find the wirings of the stepping rotors

Unimodular matrix and bernoulli map on text encryption algorithm using python

One of the encryption algorithms is the Hill Cipher. The square key matrix in the Hill Cipher method must have an inverse modulo. The unimodular matrix is one of the few matrices that must have an inverse. A unimodular matrix can be utilized as a key in the encryption process. This research aims to demonstrate that there is another approach to protect text message data. Symmetric cryptography is the sort of encryption utilized. A Bernoulli Map is used to create a unimodular matrix. To begin, the researchers use an identity matrix to generate a unimodular matrix. The Bernoulli Map series of real values in (0,1) is translated to integers between 0 and 255. The numbers are then inserted into the unimodular matrix's top triangular entries. To acquire the full matrix as the key, the researchers utilize Elementary Row Operations. The data is then encrypted using modulo matrix multiplication

Slippery hill-climbing technique for ciphertext-only cryptanalysis of periodic polyalphabetic substitution ciphers

We present a stochastic method for breaking general periodic polyalphabetic substitution ciphers using only the ciphertext and without using any additional constraints that might come from the cipher’s structure. The method employs a hill-climbing algorithm for individual key alphabets, with occasional slipping down the hill. We implement the method with a computer and achieve reliable results for a sufficiently long ciphertext (150 characters per key alphabet). Because no constraints among the key alphabets are used, this method applies to any periodic polyalphabetic substitution cipher

Some cryptographic algorithms

Cryptography is the practice and study of techniques for secure communication in the presence of third parties, called adversaries. Modern cryptography is heavily based on mathematical theory and computer science practice. Cryptographic algorithms are designed so that in practice they are hard to break by any adversary. In the present thesis consisting of two chapters first we have given a brief review of some important number theoretic concepts and results. Then we have discussed S-DES and DES algorithms for Secret key cryptography, RSA and DSA algorithms for Public key cryptography and at last a brief introduction of elliptic curves and their use in Cryptography is given

Cryptanalysis of an image encryption scheme based on the Hill cipher

This paper studies the security of an image encryption scheme based on the Hill cipher and reports its following problems: 1) there is a simple necessary and sufficient condition that makes a number of secret keys invalid; 2) it is insensitive to the change of the secret key; 3) it is insensitive to the change of the plain-image; 4) it can be broken with only one known/chosen-plaintext; 5) it has some other minor defects.Comment: 10 pages, three figure