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For example, in a Caesar cipher of shift 3, a would become D, b would become E, y would become B and so on. The Vigenère cipher has several Caesar ciphers in sequence with different shift values. To encrypt, a table of alphabets can be used, termed a tabula recta, Vigenère square or Vigenère table. It has the alphabet written out 26 times in ...
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.
The Vigenère cipher is probably the most famous example of a polyalphabetic substitution cipher. [21] The famous cipher machines of World War II encipher in a polyalphabetic system. Their strength came from the enormous number of well-mixed alphabets that they used and the fairly random way of switching between them.
In 1863, Kasiski published a 95-page book on cryptography, Die Geheimschriften und die Dechiffrir-Kunst (German, "Secret writing and the Art of Deciphering"). This was the first published account of a procedure for attacking polyalphabetic substitution ciphers, especially the Vigenère cipher (although it is possible Charles Babbage was already aware of a similar method but had not published it).
Bellaso's third book was printed in 1564 and dedicated to Alessandro Farnese. It recapitulates the preceding ciphers, with many new variations with regard to their usage. All tables are used with or without countersigns or index letters. The encipherment is performed word-by-word or one letter at a time.
1450–1520 – The Voynich manuscript, an example of a possibly encoded illustrated book, is written. 1466 – Leon Battista Alberti invents polyalphabetic cipher, also first known mechanical cipher machine; 1518 – Johannes Trithemius' book on cryptology; 1553 – Bellaso invents Vigenère cipher; 1585 – Vigenère's book on ciphers
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A polyalphabetic cipher is a substitution, using multiple substitution alphabets. The Vigenère cipher is probably the best-known example of a polyalphabetic cipher, though it is a simplified special case. The Enigma machine is more complex but is still fundamentally a polyalphabetic substitution cipher.