This cipher is more complex than mono alphabetic substitution. Its key is a word, such as “CHAIR.” The rule of the cipher is similar to that of the Caesar shift cipher, except it changes with every letter according to the keyword. The first letter of a message with key word CHAIR would be encoded with the C cipher alphabet, the second with the H cipher alphabet, and it continues like this through the keyword. The keyword is only five letters long, so for the sixth letter of the message a C cipher is used again. The Vigenère cipher was thought to be unbreakable for a long time. To decipher, first the length of the keyword is guessed. If the keyword is guessed to be five letters long, then letters numbered 1, 6, 11, 16, 21, etc. will all correspond to the first letter of the keyword, and letter frequency analysis will decipher them. The decoder then moves to letters 2, 7, 12, 17, and so on. If the keyword is indeed five letters long, this will decode the cipher. If not, another keyword length must be guessed and the process repeated.
Eoaqiu hs net hs byg lym tcu smv dot vfv h petrel tw jka.
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Codes and Ciphers
RandomThe need to conceal the meaning of important messages has existed for thousands of years. Over time, people have found increasingly complex ways of encoding their messages as the simpler ways are decoded with greater ease. Contrary to layman-speak...
