The Free On-line Dictionary of Computing (30 December 2018):
Tunny Emulator
A special-purpose computer designed
at Bletchley Park (UK) based upon the reverse engineering of
the Lorenz Cypher. The Lorenz Cypher was used by the German
army to encrypt high command orders for transmission via
teleprinter (the Enigma was a field-use cypher).
Once the key to a message was discovered (by the computer
Colossus) the Tunny machine would be set to decrypt the
message. The process took about four days from intercept to
printout. The original Tunny machine was built about 1943 and
scrapped after the war. In 2011 a working model was re-built
at Bletchley Park where it is on display.
(2012-03-25)