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  2. Substitution cipher - Wikipedia

    en.wikipedia.org/wiki/Substitution_cipher

    A monoalphabetic cipher uses fixed substitution over the entire message, whereas a polyalphabetic cipher uses a number of substitutions at different positions in the message, where a unit from the plaintext is mapped to one of several possibilities in the ciphertext and vice versa.

  3. Frequency analysis - Wikipedia

    en.wikipedia.org/wiki/Frequency_analysis

    Several schemes were invented by cryptographers to defeat this weakness in simple substitution encryptions. These included: Homophonic substitution: Use of homophones — several alternatives to the most common letters in otherwise monoalphabetic substitution ciphers. For example, for English, both X and Y ciphertext might mean plaintext E.

  4. Aristocrat Cipher - Wikipedia

    en.wikipedia.org/wiki/Aristocrat_Cipher

    The Aristocrat Cipher is a type of monoalphabetic substitution cipher in which plaintext is replaced with ciphertext and encoded into assorted letters, numbers, and symbols based on a keyword. The formatting of these ciphers generally includes a title, letter frequency, keyword indicators, and the encoder's nom de plume . [ 1 ]

  5. Affine cipher - Wikipedia

    en.wikipedia.org/wiki/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 essentially a ...

  6. Cryptanalysis - Wikipedia

    en.wikipedia.org/wiki/Cryptanalysis

    Frequency analysis relies on a cipher failing to hide these statistics. For example, in a simple substitution cipher (where each letter is simply replaced with another), the most frequent letter in the ciphertext would be a likely candidate for "E". Frequency analysis of such a cipher is therefore relatively easy, provided that the ciphertext ...

  7. Polybius square - Wikipedia

    en.wikipedia.org/wiki/Polybius_square

    The Polybius square is also used as a basic cipher called the Polybius cipher. This cipher is quite insecure by modern standards, as it is a substitution cipher with characters being substituted for pairs of digits, which is easily broken through frequency analysis. [2]

  8. Known-plaintext attack - Wikipedia

    en.wikipedia.org/wiki/Known-plaintext_attack

    Classical ciphers are typically vulnerable to known-plaintext attack. For example, a Caesar cipher can be solved using a single letter of corresponding plaintext and ciphertext to decrypt entirely. A general monoalphabetic substitution cipher needs several character pairs and some guessing if there are fewer than 26 distinct pairs.

  9. Timeline of cryptography - Wikipedia

    en.wikipedia.org/wiki/Timeline_of_cryptography

    600-500 – Hebrew scholars make use of simple monoalphabetic substitution ciphers (such as the Atbash cipher) c. 400 – Spartan use of scytale (alleged) c. 400 – Herodotus reports use of steganography in reports to Greece from Persia (tattoo on shaved head) 100-1 A.D.- Notable Roman ciphers such as the Caesar cipher.