cryptanalysis
Cryptanalysis is the art of reconstructing the plaintext from a given ciphertext without knowing the key. Obviously, the purpose of cryptography is to make cryptanalysis a hard task.
shift cipher
substitution cipher
affine cipher
vigenere cipher
more information:
Vigenere table
more frequency analysis for English text 1
more frequency analysis for English text 2
created by A. Betten, August 23, 2003, last change August 23, 2003