Kiss (cryptanalysis)
In cryptanalysis, a kiss is a pair of identical messages sent using different ciphers, one of which has been broken. The term was used at Bletchley Park during World War II. A deciphered message in the breakable system provided a "crib" which could then be used to read the unbroken messages. One example was where messages read in a German meteorological cipher could be used to provide cribs for reading the difficult 4-wheel Naval Enigma cipher.
