nRepeated XOR
mask
nPick a key
number. XOR with each plaintext
nXOR
with key again to decrypt
nINSECURE: just one
plaintext/ciphertext gives the key
nMonoalphabetic
substitution
nKey is a table of
letters and corresponding ciphertexts
na=m,
b-x, c=b, d=r, etc.
nencrypt/decrypt
by substitution
nExhaustive search is
really hard (26! keys to try).
nINSECURE:
statistical analysis of ciphertext frequency