Cryptography

An automatic cryptanalysis of simple substitution ciphers using compression

“…This will still happen even if the character frequencies of the ciphertext is different from those of normal English text. With a few attempts and after trying some of the possibilities, the cryptanalyst will be able to find the correct substitution (Irvine, 1997;Eskicioglu & Litwin, 2001). Digram and trigram distributions provide more useful information that can also be accessed by the cryptanalyst.…”

“…Despite the fact that simple substitution ciphers are not typically used in real-world encoding systems nowadays, many effective and secure modern ciphers use substitution ciphers in combination with other ciphers, for example, transposition ciphers, modular arithmetic, Boolean algebra and so on. This powerful combination is an important innovation as it results in a method that is stronger than its original components (Eskicioglu & Litwin, 2001). Although monoalphabetic ciphers are not considered secure, they are frequently used as building blocks in larger state of the art cryptographic systems.…”

An efficient algorithm for Polyalphabetic substitution using random tables

“…Cryptanalysis of classical ciphers is made possible because of the redundancy in the linguistic structure of natural languages [5]. In monoalphabetic substitution cipher, the most frequent letters in the ciphertext corresponds to the most frequent letters in the plaintext.…”

Survey: Recent Modifications in Vigenere Cipher

“…If a cryptanalyst correctly find the key's length, then the cipher text can be easily broken [9]. Cryptanalysis of the Vigenere cipher has 2 main steps, first one is to identify the period of the cipher (the length of the key), then find the specific key.…”

“…Cryptanalysis of classical ciphers is made possible because of the redundancy in the linguistic structure of natural languages [9]. The most frequent letters in the ciphertext are simply shifted versions of the most frequent letters in the plaintext.…”