United States Diplomatic Codes and Ciphers, 1775-1938 is the first basic reference work on American diplomatic cryptography. Weber's research in national and private archives in the Americas and Europe has uncovered more than one hundred codes and ciphers. Beginning with the American Revolution, these secret systems masked confidential diplomatic correspondence and reports.

During the period between 1775 and 1938, both codes and ciphers were employed. Ciphers were frequently used for American diplomatic and military correspondence during the American Revolution. At that time, a...