Frode Weierud
and Olaf Ostwald have written the interesting article ‘Modern breaking of Enigma cipher texts’ on modern techniques used in solving
original Enigma messages from WWII.
ABSTRACT
“Breaking German Army Ciphers” is the
title of a Cryptologia article
from 2005, describing the lucky survival of several hundred authentic Enigma
messages of World War II, and an account of a ciphertext-only cryptanalysis of
a large number of these messages, leaving only a few (mostly short messages)
unbroken. After reviewing the work done, and investigating the reasons for both
lucky breaks and close misses, the modern ciphertext-only attack on Enigma
messages is improved, especially on genuine ones with short lengths and/or many
garbles. The difficulties of a proper measure for the candidate’s closeness to
a plaintext are clarified. The influence on the decryption process of an empty
plugboard and one with only a few correct plugs is examined. The method is
extended by a partial exhaustion of the plugboard combined with an optimized
hillclimbing strategy. The newly designed software succeeds in breaking
formerly unbroken messages.
Frode has also summarized the previous efforts
to solve these messages at CryptoCellar
Tales.
No comments:
Post a Comment