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Since the affine cipher is still a monoalphabetic substitution cipher, it inherits the weaknesses of that class of ciphers. The Caesar cipher is an Affine cipher with a = 1 since the encrypting function simply reduces to a linear shift. The Atbash cipher uses a = −1. Considering the specific case of encrypting messages in English (i.e. m = 26 ...
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. [ 4][ 5]
In cryptanalysis, frequency analysis (also known as counting letters) is the study of the frequency of letters or groups of letters in a ciphertext. The method is used as an aid to breaking classical ciphers . Frequency analysis is based on the fact that, in any given stretch of written language, certain letters and combinations of letters ...
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 ...
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 ...
Encryption. The Atbash cipher is a particular type of monoalphabetic cipher formed by taking the alphabet (or abjad, syllabary, etc.) and mapping it to its reverse, so that the first letter becomes the last letter, the second letter becomes the second to last letter, and so on. For example, the Latin alphabet would work like this: Plain. A. B. C.
Known-plaintext attack. The known-plaintext attack ( KPA) is an attack model for cryptanalysis where the attacker has access to both the plaintext (called a crib) and its encrypted version ( ciphertext ). These can be used to reveal secret keys and code books. The term "crib" originated at Bletchley Park, the British World War II decryption ...
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 ...