In 1931, federal agents raided a New Orleans stash of liquor illegally imported from Vancouver. There were 104 people indicted in an elaborate scheme that was cracked when coded messages were intercepted. To convict all those people, special prosecutor Colonel Amos W. Woodcock had to lead the jury through the process of decrypting the coded messages the smuggling ring used.
To convict the accused, Woodcock had to link them to hundreds—if not thousands—of encrypted messages that passed between at least 25 separate ships, their shore stations, and the headquarters in New Orleans. Defense attorneys demanded to know how the government could prove the content of enciphered messages. How, for example, could a cryptanalyst know that "MJFAK ZYWKB QATYT JSL QATS QXYGX OGTB" translated to "anchored in harbor where and when are you sending fuel?"*
Elizebeth Friedman, the prosecution's star witness, asked the judge to find a chalkboard.
Using a piece of chalk, she stood before the jury and explained the basics of cryptanalysis. Friedman talked about simple cipher charts, mono-alphabetic ciphers and polysyllabic ciphers; she reviewed how cryptanalysts encoded messages by writing keywords in lines of code, enclosing them with letter patterns that could be deciphered with the help of various code books and charts rooted in the schemes and charts of centuries past.
The defense did not want her to stay on the stand for long.
Working for the Coast Guard, between 1928 and 1930, Friedman and her assistant deciphered 12,000 encryptions that used 50 different codes. The work had to be handled with utmost care due to the general unpopularity of Prohibition as well as the government’s strained diplomatic relations with Canada. Read how Elizebeth Friedman, an Indiana farm girl, rose to the occasion and then established a permanent cryptanalytic unit for the Coast Guard, at Smithsonian.