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Affine cipher. The affine cipher is a type of monoalphabetic substitution cipher, where each letter in an alphabet is mapped to its numeric equivalent, encrypted using a simple mathematical function, and converted back to a letter. The formula used means that each letter encrypts to one other letter, and back again, meaning the cipher is ...
The Atbash cipher can be seen as a special case of the affine cipher. Under the standard affine convention, an alphabet of m letters is mapped to the numbers 0, 1, ... , m − 1. (The Hebrew alphabet has m = 22, and the standard Latin alphabet has m = 26). The Atbash cipher may then be enciphered and deciphered using the encryption function for ...
In cryptanalysis, Kasiski examination (also known as Kasiski's test or Kasiski's method) is a method of attacking polyalphabetic substitution ciphers, such as the Vigenère cipher. [ 1 ] [ 2 ] It was first published by Friedrich Kasiski in 1863, [ 3 ] but seems to have been independently discovered by Charles Babbage as early as 1846.
Linear cryptanalysis. In cryptography, linear cryptanalysis is a general form of cryptanalysis based on finding affine approximations to the action of a cipher. Attacks have been developed for block ciphers and stream ciphers. Linear cryptanalysis is one of the two most widely used attacks on block ciphers; the other being differential ...
Symmetric-key algorithm. Symmetric-key algorithms[ a] are algorithms for cryptography that use the same cryptographic keys for both the encryption of plaintext and the decryption of ciphertext. The keys may be identical, or there may be a simple transformation to go between the two keys. [ 1] The keys, in practice, represent a shared secret ...
In a chosen-plaintext attack the adversary can (possibly adaptively) ask for the ciphertexts of arbitrary plaintext messages. This is formalized by allowing the adversary to interact with an encryption oracle, viewed as a black box. The attacker’s goal is to reveal all or a part of the secret encryption key. It may seem infeasible in practice ...
Unicity distance. In cryptography, unicity distance is the length of an original ciphertext needed to break the cipher by reducing the number of possible spurious keys to zero in a brute force attack. That is, after trying every possible key, there should be just one decipherment that makes sense, i.e. expected amount of ciphertext needed to ...
A disk cipher device of the Jefferson type from the 2nd quarter of the 19th century in the National Cryptologic Museum. The Jefferson disk, also called the Bazeries cylinder or wheel cypher, [1] was a cipher system commonly attributed to Thomas Jefferson that uses a set of wheels or disks, each with letters of the alphabet arranged around their edge in an order, which is different for each ...