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  2. Vigenère cipher - Wikipedia

    en.wikipedia.org/wiki/Vigenère_cipher

    in which c is the size of the alphabet (26 for English), N is the length of the text and n 1 to n c are the observed ciphertext letter frequencies, as integers. That is, however, only an approximation; its accuracy increases with the length of the text. It would, in practice, be necessary to try various key lengths that are close to the ...

  3. Kasiski examination - Wikipedia

    en.wikipedia.org/wiki/Kasiski_examination

    Kasiski actually used "superimposition" to solve the Vigenère cipher. He started by finding the key length, as above. Then he took multiple copies of the message and laid them one-above-another, each one shifted left by the length of the key. Kasiski then observed that each column was made up of letters encrypted with a single alphabet. His ...

  4. Giovan Battista Bellaso - Wikipedia

    en.wikipedia.org/wiki/Giovan_Battista_Bellaso

    This cipher is a letter-by-letter polysubstitution using a long literal key string. 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 ...

  5. 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 ...

  6. Beaufort cipher - Wikipedia

    en.wikipedia.org/wiki/Beaufort_cipher

    Due to the similarities between the Beaufort cipher and the Vigenère cipher it is possible, after applying a transformation, to solve it as a Vigenère cipher. By replacing every letter in the ciphertext and key with its opposite letter (such that 'a' becomes 'z', 'b' becomes 'y' etc.; i.e. an Atbash -transformation) it can be solved like a ...

  7. Classical cipher - Wikipedia

    en.wikipedia.org/wiki/Classical_cipher

    The cipher alphabet on the second row uses B for A and C for B etc. That is cipher alphabet 'B'. Each cipher alphabet is named by the first letter in it. For example, if the keyword is LEMON and the message to encode is ATTACKATDAWN, then the encoding is:

  8. 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 ...

  9. Blaise de Vigenère - Wikipedia

    en.wikipedia.org/wiki/Blaise_de_Vigenère

    On Vigenère's trips to Italy he read books about cryptography and came in contact with cryptologists. Giovan Battista Bellaso described a method of encryption in his 1553 book La cifra del. Sig. Giovan Battista Belaso, published in Venice in 1553, [16] which in the 19th century was misattributed to Vigenère and became widely known as the "Vigenère cipher". [17]