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  2. Vigenère cipher - Wikipedia

    en.wikipedia.org/wiki/Vigenère_cipher

    Kasiski entirely broke the cipher and published the technique in the 19th century, but even in the 16th century, some skilled cryptanalysts could occasionally break the cipher. [9] Cryptographic slide rule used as a calculation aid by the Swiss Army between 1914 and 1940.

  3. Kasiski examination - Wikipedia

    en.wikipedia.org/wiki/Kasiski_examination

    In polyalphabetic substitution ciphers where the substitution alphabets are chosen by the use of a keyword, the Kasiski examination allows a cryptanalyst to deduce the length of the keyword. Once the length of the keyword is discovered, the cryptanalyst lines up the ciphertext in n columns, where n is the length of the keyword.

  4. Unicity distance - Wikipedia

    en.wikipedia.org/wiki/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 determine the key ...

  5. Giovan Battista Bellaso - Wikipedia

    en.wikipedia.org/wiki/Giovan_Battista_Bellaso

    It is very similar to the Vigenère cipher, making many scholars call Bellaso its inventor, although unlike the modern Vigenère cipher Bellaso didn't use 26 different "shifts" (different Caesar's ciphers) for every letter, instead opting for 13 shifts for pairs of letters. The system is still periodic although the use of one or more long ...

  6. 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.

  7. Cryptanalysis - Wikipedia

    en.wikipedia.org/wiki/Cryptanalysis

    Reconstruction of the appearance of cyclometer, a device used to break the encryption of the Enigma machine.Based on sketches in Marian Rejewski's memoirs.. Cryptanalysis (from the Greek kryptós, "hidden", and analýein, "to analyze") refers to the process of analyzing information systems in order to understand hidden aspects of the systems. [1]

  8. Polyalphabetic cipher - Wikipedia

    en.wikipedia.org/wiki/Polyalphabetic_cipher

    The cipher was trivial to break, and Alberti's machine implementation not much more difficult. Key progression in both cases was poorly concealed from attackers. Even Alberti's implementation of his polyalphabetic cipher was rather easy to break (the capitalized letter is a major clue to the cryptanalyst).

  9. National Cipher Challenge - Wikipedia

    en.wikipedia.org/wiki/National_Cipher_Challenge

    In later challenges the cryptograms become harder to break. [3] In the past, part A cryptograms have been encrypted with the Caesar cipher, the Affine cipher, the Keyword cipher, the Transposition cipher, the Vigenère cipher and the 2x2 Hill cipher. The part B challenges are intended to be harder.