Alan Turing was an English mathematician, computer scientist, logician, cryptanalyst, philosopher and theoretical biologist. Krell's character is loosely based on the British cryptanalyst, Alan Turing. The cryptanalyst hypothesised one plugboard interconnection for the bombe to test. A cryptanalyst must break both ciphers to get any information. In classical cryptography, a "null" is intended to confuse the cryptanalyst. A cryptanalyst would prepare a crib for comparison with the ciphertext. Joan Clarke was one of the few women employed at Bletchley as a full-fledged cryptanalyst. Navy cryptanalyst Joseph Rochefort thought AF was Midway Island. It was later broken by the famous French cryptanalyst Georges Painvin. She has been called "America's first female cryptanalyst". In 1923, Friedman was hired as a cryptanalyst for the U.S. Navy. Although neither was quite certain what a cryptanalyst did, they accepted. After this, his professional responsibilities as a senior cryptanalyst limited his top-class appearances. This can give strong hints to the cryptanalyst unless the message is superenciphered. The cryptanalyst has to rule out the coincidences to find the correct length.