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The Beaufort cipher, created by Sir Francis Beaufort, is a substitution cipher similar to the Vigenère cipher, with a slightly modified enciphering mechanism and tableau.〔Franksen, Ole Immanuel, ''Babbage and cryptography. Or, the mystery of Admiral Beaufort's cipher''. Mathematics and Computers in Simulation 35 (1993) 327-367〕 Its most famous application was in a rotor-based cipher machine, the Hagelin M-209.〔Mollin, Richard A., ''An Introduction to Cryptography'', page 100. Chapman & Hall/CRC, 2001〕 ==Using the cipher== To encrypt, first choose the plaintext character from the top row of the tableau, call this column P. Secondly, travel down column P to the corresponding key Letter K. Finally, move directly left from the Key letter to the left edge of the tableau, the CipherText encryption of Plaintext P with Key K will be there. For example if encrypting Plain text character "d" with Key "m" the steps would be: # find the column with "d" on the top, # travel down that column to find Key "m", # travel to the left edge of the tableau to find the CipherText letter ("J" in this case). To decrypt, the process is reversed. The Beaufort cipher is a reciprocal cipher, that is, Decryption and Encryption algorithms are the same. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Beaufort cipher」の詳細全文を読む スポンサード リンク
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