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  2. 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.

  3. Vigenère cipher - Wikipedia

    en.wikipedia.org/wiki/Vigenère_cipher

    Despite the Vigenère cipher's apparent strength, it never became widely used throughout Europe. The Gronsfeld cipher is a variant attributed by Gaspar Schott to Count Gronsfeld (Josse Maximilaan van Gronsveld né van Bronckhorst) but was actually used much earlier by an ambassador of Duke of Mantua in 1560s-1570s. It is identical to the ...

  4. Cryptanalysis - Wikipedia

    en.wikipedia.org/wiki/Cryptanalysis

    Bruce Schneier notes that even computationally impractical attacks can be considered breaks: "Breaking a cipher simply means finding a weakness in the cipher that can be exploited with a complexity less than brute force. Never mind that brute-force might require 2 128 encryptions; an attack requiring 2 110 encryptions would be considered a ...

  5. 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 ...

  6. 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 ...

  7. 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]

  8. Cryptography - Wikipedia

    en.wikipedia.org/wiki/Cryptography

    Cryptanalysis of symmetric-key ciphers typically involves looking for attacks against the block ciphers or stream ciphers that are more efficient than any attack that could be against a perfect cipher. For example, a simple brute force attack against DES requires one known plaintext and 2 55 decryptions, trying approximately half of the ...

  9. History of cryptography - Wikipedia

    en.wikipedia.org/wiki/History_of_cryptography

    These keys convert the messages and data into "digital gibberish" through encryption and then return them to the original form through decryption. In general, the longer the key is, the more difficult it is to crack the code. This holds true because deciphering an encrypted message by brute force would require the attacker to try every possible ...