The Vigenère cipher has several Caesar ciphers in sequence with different shift values. For example, in a Caesar cipher of shift 3, a would become D, b would become E, y would become B and so on. In a Caesar cipher, each letter of the alphabet is shifted along some number of places. 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. Charles Babbage is known to have broken a variant of the cipher as early as 1854 but did not publish his work. In 1917, Scientific American described the Vigenère cipher as "impossible of translation". Noted author and mathematician Charles Lutwidge Dodgson ( Lewis Carroll) called the Vigenère cipher unbreakable in his 1868 piece " The Alphabet Cipher" in a children's magazine.
The Vigenère cipher gained a reputation for being exceptionally strong. David Kahn, in his book, The Codebreakers lamented this misattribution, saying that history had "ignored this important contribution and instead named a regressive and elementary cipher for him though he had nothing to do with it". In the 19th century, the invention of Bellaso's cipher was misattributed to Vigenère. As it is relatively easy to secure a short key phrase, such as by a previous private conversation, Bellaso's system was considerably more secure. Bellaso's method thus required strong security for only the key. Keys were typically single words or short phrases, known to both parties in advance, or transmitted "out of band" along with the message. Whereas Alberti and Trithemius used a fixed pattern of substitutions, Bellaso's scheme meant the pattern of substitutions could be easily changed, simply by selecting a new key. He built upon the tabula recta of Trithemius but added a repeating "countersign" (a key) to switch cipher alphabets every letter.
The cipher now known as the Vigenère cipher, however, is that originally described by Giovan Battista Bellaso in his 1553 book La cifra del Sig. In 1586 Blaise de Vigenère published a type of polyalphabetic cipher called an autokey cipher – because its key is based on the original plaintext – before the court of Henry III of France. The Trithemius cipher, however, provided a progressive, rather rigid and predictable system for switching between cipher alphabets. Later, Johannes Trithemius, in his work Polygraphiae (which was completed in manuscript form in 1508 but first published in 1518), invented the tabula recta, a critical component of the Vigenère cipher. Alberti's system only switched alphabets after several words, and switches were indicated by writing the letter of the corresponding alphabet in the ciphertext. Specializing in Specializing in fence materials, including custom wood picket, privacy chain link slats, vinyl arbors, razor and welded wire.The very first well-documented description of a polyalphabetic cipher was by Leon Battista Alberti around 1467 and used a metal cipher disk to switch between cipher alphabets. Covers background theories, encryption, authentication, network security, databases, minimum knowledge systems, and security in operating systems. A dot is made for each letter of the message in the proper column, reading from top to bottom of the sheet. As described in Fletcher Pratt's Secret and Urgent, it is "written by ruling a sheet of paper in vertical columns, with a letter at the head of each column.
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