Book cipher
From Free net encyclopedia
Revision as of 06:58, 21 July 2005; view current revision
←Older revision | Newer revision→
←Older revision | Newer revision→
A book cipher is a cipher in which the key is the identity of a book.
Traditionally book ciphers work by replacing words in the plaintext of a message with the location of words from a book. In this mode, book ciphers are more properly called codes.
This can have problems as if a word appears in the plaintext that doesn't appear in the book then it can't be encoded. An alternative approach which gets around this problem is to replace individual letters rather than words, in which case the book cipher is properly a cipher. However, if needed often, this has the side effect of creating a larger ciphertext.
Perhaps the most famous use of a book cipher is in the Beale ciphers.
- See also: Running key cipher
Classical cryptography edit |
Ciphers: ADFGVX | Affine | Atbash | Autokey | Bifid | Book | Caesar | Four-square | Hill | Nihilist | Permutation | Pigpen | Playfair | Polyalphabetic | Reihenschieber | Reservehandverfahren | Running key | Substitution | Transposition | Trifid | Two-square | Vigenère
|
Cryptanalysis: Frequency analysis | Index of coincidence |
Misc: Cryptogram | Polybius square | Scytale | Straddling checkerboard | Tabula recta |