Description based on online resource, PDF version; title from title page (viewed November 1, 2016).
Bibliography
Includes bibliographical references and indexes.
Note
At head of title: War Department. Office of the Chief Signal Officer, Washington.
"Prepared under the direction of the Chief Signal Officer."
Contents
pt. 1. Monoalphabetic substitution systems -- pt. 2. Simpler varieties of polyalphabetic substitution systems -- pt. 3. Simpler varieties of aperiodic substitution systems -- pt. 4. Transportation and fractionating systems.
Note
"Declassified and approved for release by NSA on 09-19-2005 pursuant to E.O. 12958, as amended."