New York, NY: Bell Telephone Laboratories, Incorporated April 1950. First Separate Edition. 60 pages. 11 x 8 1/2 inches. Original printed grey, blue and black wrappers, stapled. Five holes punched at the spine as issued. There are several small color splotches on the covers; otherwise, very nice. Near Fine. Wraps. 
During World War II, Bell Lab scientists worked on classified government-funded cryptography research. Shannon's research resulted in the classified internal technical memorandum "A Mathematical Theory of Cryptography" dated Sept. 1, 1945. (Sloane and Wyner #24) Never published, the Bell System Technical Journal (BSTJ) in October 1949 first published a declassified abstract of this paper titled "Communication Theory of Secrecy Systems." (Sloan and Wyner #25)
Offered here is the first separate edition, as issued in the Bell Telephone System Monograph series (#1727: April 1950). We are unaware of any separately issued Bell System Technical Journal offprint for this paper.
"Shannon’s insight, his great contribution to cryptology, lay in pointing out that [language] redundancy furnishes the ground for cryptanalysis. 'In ... the majority of ciphers,' he wrote, 'it is only the existence of redundancy in the original messages that makes a solution possible.' This is the very basis of codebreaking." (Kahn 1996, p 748)
"The discoverer of information theory examines cryptology in terms of that theory: redundancy, entropy, equivocation. Shannon develops formulas that enable the cryptanalyst to tell when a solution in a particular cipher system is valid. He discusses perfect secrecy (the absolutely unbreakable cipher) and ideal secrecy (practically unbreakable ciphers) and work characteristics needed to solve different kinds of ciphers. (Kahn 1969, pp 324-5)
"[Communication theory of secrecy systems] has provided, for the first time, a well-organized theory of cryptography and cryptanalysis, and it is highly regarded by the expert cryptanalysts." (Pierce, p 271)
PROVENANCE: The personal files of Claude E. Shannon (unmarked). There were six examples of this item in Shannon's files.
REFERENCES: (all referring to “Communication Theory of Secrecy Systems”)
Sloane and Wyner, "Claude Elwood Shannon Collected Papers," #24 and #25
Shulman, David, "Theoretical and mathematical aspects of ciphers" in "An Annotated Bibliography of Cryptography" (Garland: 1976), p 122.
Kahn, David 1969, "Secret Writings: Selected Works on Modern Cryptography" in Bulletin of the New York Public Library, May 1969.
Kahn, David 1996, "The Code Breakers: A Comprehensive History of the Secret Communication from Ancient Times to the Internet" (Scribners, 1996, revised edition)
Pierce, John R., "An Introduction to Information Theory" (Dover: 1980)
COLLECTORS NOTE: The Bell Telephone System Monograph series offered a way to obtain individual articles by Bell scientists regardless of where their work was first published. Many Monographs significantly postdate the original article publication. Because of this, they rarely constitute the coveted (and traditional) article offprint. If the journal of record issued no offprint, the Monograph might be the first separate publication - the closest the collector can come to a traditional offprint. We have done our best to place each Monograph properly in the article’s publishing history and welcome any corrections or additional information, especially regarding issues unknown to us.