Viewing Single Post From: Announcement: Official Vigenère Tutorial

Viewing Single Post From: Announcement: Official Vigenère Tutorial
Revelation	Oct 6 2005, 03:42 PM
Administrator Posts: 386 Group: Admin Member #1 Joined: August 23, 2005	Well, this is version one. It contains some background info, but no cracking methods yet. Feel free to edit it and write some more Quote: The Vigenère cipher is a method of encryption that uses a series of different Caesar ciphers based on the letters of a keyword. It is a simplified version of the more general polyalphabetic substitution cipher, invented by Alberti circa 1465. The invention of the Vigenère cipher was misattributed to Blaise de Vigenère in the 19th century; it was originally described by a Giovan Batista Belaso in his 1553 book La cifra del. Sig. Giovan Batista Belaso. Source: Wikipedia As said in the quote above, the Vigenère cipher consists of numerous Caesar ciphers. In a Caesar cipher (shift cipher) the alphabet is shifted by a fixed number. For an example, the plain text ‘gamma’ is shifted by 3: ABCDEFGHIJKLMNOPQRSTUVWXYZ DEFGHIJKLMNOPQRSTUVWXYZABC GAMMA JDPPD The Vigenère cipher uses shifts too, but the main differences are that the fixed number is a letter and that multiple letters are used. Lets start with the first one. Lets say we want to use letter K for the shift: ABCDEFGHIJKLMNOPQRSTUVWXYZ turns into KLMNOPQRSTUVWXYZABCDEFGHIJ That wasn’t that hard, was it? Now onto the multiple shifts. The fixed numbers (password) shall now be referred to as the key. The key for the next example will be hello. Code: `ABCDEFGHIJKLMNOPQRSTUVWXYZ H: HIJKLMNOPQRSTUVWXYZABCDEFG E: EFGHIJKLMNOPQRSTUVWXYZABCD L: LMNOPQRSTUVWXYZABCDEFGHIJK L: LMNOPQRSTUVWXYZABCDEFGHIJK O: OPQRSTUVWXYZABCDEFGHIJKLMN` Now, you can find the right ciphered letter by looking at the offset of your plaintext letter. If this is at position 1, the letter will be replaced by the one with the same alphabetical offset in alphabet H. The letter at position 2 is encrypted with E, etc. So the plain text ‘ape’ with key ‘hello’ would become HTP. If the length of the plain text exceeds the length of the key, the key is repeated. For example: Code: `Plaintext: ATTACKATDAWN Key: LEMONLEMONLE ( original key: LEMON) Cipher text: LXFOPVEFRNHR`
	RRRREJMEEEEEPVKLWENFNVJKEEEEEAOLKAFKLXCFZAASDJXZTTTTTTTLSIOWJXMOKLAFJNNKFNXN RAGRBAQEMHIGDJVDSEOXVIYCELFHWLELJFIENXLRATALSJFSLCYTKLASJDKMHGOVOKAJDNMNUITN RRRRLJVEEEEECLYVYHNVPFTAEEEEEMWLMEIRNGLARWJAKJDFLWNTIERJMIPQWOTZEOCXKNUBNXCN RJIRPOWEANFUSNCZVDVZNMSFEKLOEPZLDKDJWSAAAAAAAOERHJCTNCKFRIMVKSOFOMKMANREWNBN RZUDRGXEEEEENFQIDVLQNCKNEEEEEDGLLLLLLAWIOSNCDARLODMTOEJXMILDFJROTKJSDNLVCZNN

Announcement: Official Vigenère Tutorial · News