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  2. Vigenère cipher - Wikipedia

    en.wikipedia.org/wiki/Vigenère_cipher

    If it is assumed that the repeated segments represent the same plaintext segments, that implies that the key is 18, 9, 6, 3, 2, or 1 characters long. The distance between the repetitions of QUCE is 30 characters. That means that the key length could be 30, 15, 10, 6, 5, 3, 2, or 1 characters long.

  3. The Alphabet Cipher - Wikipedia

    en.wikipedia.org/wiki/The_Alphabet_Cipher

    "The Alphabet Cipher" was a brief study published by Lewis Carroll in 1868, describing how to use the alphabet to send encrypted codes. [1] It was one of four ciphers he invented between 1858 and 1868, and one of two polyalphabetic ciphers he devised during that period and used to write letters to his friends. [2]

  4. Kasiski examination - Wikipedia

    en.wikipedia.org/wiki/Kasiski_examination

    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]

  5. Unicity distance - Wikipedia

    en.wikipedia.org/wiki/Unicity_distance

    Now an alphabet of 32 characters can carry 5 bits of information per character (as 32 = 2 5). In general the number of bits of information per character is log 2 (N), where N is the number of characters in the alphabet and log 2 is the binary logarithm. So for English each character can convey log 2 (26) = 4.7 bits of information.

  6. Polyalphabetic cipher - Wikipedia

    en.wikipedia.org/wiki/Polyalphabetic_cipher

    [2] The Alberti cipher by Leon Battista Alberti around 1467 was an early polyalphabetic cipher. Alberti used a mixed alphabet to encrypt a message, but whenever he wanted to, he would switch to a different alphabet, indicating that he had done so by including an uppercase letter or a number in the cryptogram.

  7. Tabula recta - Wikipedia

    en.wikipedia.org/wiki/Tabula_recta

    In 1553, an important extension to Trithemius's method was developed by Giovan Battista Bellaso, now called the Vigenère cipher. [3] Bellaso added a key, which is used to dictate the switching of cipher alphabets with each letter. This method was misattributed to Blaise de Vigenère, who published a similar autokey cipher in 1586.

  8. Smithy code - Wikipedia

    en.wikipedia.org/wiki/Smithy_code

    The cipher was a type of polyalphabetic cipher known as a Variant Beaufort, using a keyword based on the Fibonacci sequence, namely AAYCEHMU. This is the reverse of the Vigenère cipher, which here enables decryption rather than encryption. Jackie Fisher, Captain R.N. 1883, later First Sea Lord 1904–1910, 1914–1915

  9. Timeline of cryptography - Wikipedia

    en.wikipedia.org/wiki/Timeline_of_cryptography

    1854 – Charles Wheatstone invents the Playfair cipher; c. 1854 – Babbage's method for breaking polyalphabetic ciphers (pub 1863 by Kasiski) 1855 – For the English side in Crimean War, Charles Babbage broke Vigenère's autokey cipher (the 'unbreakable cipher' of the time) as well as the much weaker cipher that is called Vigenère cipher ...