Pattern Attack

Tags

exploit cryptography

Is a possible [see page 11, attack] on simple (mono-alphabetic) substitution ciphers which exploits the occurrence of common expressions in an input. For example "The quick brown fox jumps over the lazy dog".

If you can detect the general permutation of these characters in the same positions in an input you can quickly decode their underlying mappings. For example the letter o occurs at position 13 and 18 in the plaintext. If we find a character occurs at these same positions in the ciphertext then its possible the ciphertext encodes this expression; which we can find out after substituting more characters and filling out the pattern.