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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 ...
Symmetric-key encryption can use either stream ciphers or block ciphers. [8] Stream ciphers encrypt the digits (typically bytes), or letters (in substitution ciphers) of a message one at a time. An example is ChaCha20. Substitution ciphers are well-known ciphers, but can be easily decrypted using a frequency table. [9]
The Vigenère cipher ( French pronunciation: [viʒnɛːʁ]) is a method of encrypting alphabetic text where each letter of the plaintext is encoded with a different Caesar cipher, whose increment is determined by the corresponding letter of another text, the key . For example, if the plaintext is attacking tonight and the key is ...
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 ...
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 ...
The cipher illustrated here uses a left shift of 3, so that (for example) each occurrence of E in the plaintext becomes B in the ciphertext. In cryptography , a Caesar cipher , also known as Caesar's cipher , the shift cipher , Caesar's code , or Caesar shift , is one of the simplest and most widely known encryption techniques.
Camellia is a Feistel cipher with either 18 rounds (when using 128-bit keys) or 24 rounds (when using 192- or 256-bit keys). Every six rounds, a logical transformation layer is applied: the so-called "FL-function" or its inverse. Camellia uses four 8×8-bit S-boxes with input and output affine transformations and logical operations.
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 ...