He was a cryptanalyst who surfed the government's classified intranet for sensitive information.
They were sent to Germany to interrogate German cryptanalysts and to examine equipment used in developing codes.
The more samples of ciphertext that are available, the more information the cryptanalyst has to work with in trying to break a key.
Finally, in a chosen-ciphertext attack, the cryptanalyst may be able to "choose" ciphertexts and learn their corresponding plaintexts.
Once every letter in the key is known, the cryptanalyst can simply decrypt the ciphertext and reveal the plaintext.
Once the length of the keyword is discovered, the cryptanalyst lines up the ciphertext in "n" columns, where "n" is the length of the keyword.
A cryptanalyst would prepare a crib for comparison with the ciphertext.
In refining down the set of stops for further examination, the cryptanalyst would eliminate stops that contained such a contradiction.
