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In the history of cryptography, a grille cipher was a technique for encrypting a plaintext by writing it onto a sheet of paper through a pierced sheet (of paper or cardboard or similar). The earliest known description is due to the polymath Girolamo Cardano in 1550. His proposal was for a rectangular stencil allowing single letters, syllables, or words to be written, then later read, through its various apertures. The written fragments of the plaintext could be further disguised by filling the gaps between the fragments with anodyne words or letters. This variant is also an example of steganography, as are many of the grille ciphers. ==Cardan grille and variations== (詳細はFrancis Bacon gave three fundamental conditions for ciphers. Paraphrased, these are: # a cipher method should not be difficult to use # it should not be possible for others to recover the plaintext (called 'reading the cipher') # in some cases, the presence of messages should not be suspected It is difficult to fulfil all three conditions simultaneously. Condition 3 applies to steganography. Bacon meant that a cipher message should, in some cases, not appear to be a cipher at all. The original Cardan Grille met that aim. Variations on the Cardano original, however, were not intended to fulfill condition 3 and generally failed to meet condition 2 as well. But, few if any ciphers have ever achieved this second condition, so the point is generally a cryptanalyst’s delight whenever the grille ciphers are used. The attraction of a grille cipher for users lies in its ease of use (condition 1). In short, it's very simple. 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「Grille (cryptography)」の詳細全文を読む スポンサード リンク
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