Communication Theory of Secrecy Systems

"Communication Theory of Secrecy Systems" is a paper published in 1949 by Claude Shannon discussing cryptography from the viewpoint of information theory.^[1] It is one of the foundational treatments (arguably the foundational treatment) of modern cryptography.^[2] His work has been described as a "turning point, and marked the closure of classical cryptography and the beginning of modern cryptography."^[3] It has also been described as turning cryptography from an "art to a science".^[4] It is also a proof that all theoretically unbreakable ciphers must have the same requirements as the one-time pad.

Communication Theory of Secrecy Systems

Author	Claude E. Shannon
Language	English
Subject	Cryptography
Publication date	1949
Publication place	United States

The paper serves as the foundation of secret-key cryptography, including the work of Horst Feistel, the Data Encryption Standard (DES), Advanced Encryption Standard (AES), and more.^[5] In the paper, Shannon defined unicity distance, and the principles of confusion and diffusion, which are key to a secure cipher.^[6]

Shannon published an earlier version of this research in the formerly classified report A Mathematical Theory of Cryptography, Memorandum MM 45-110-02, Sept. 1, 1945, Bell Laboratories.^[7][8] This report also precedes the publication of his "A Mathematical Theory of Communication", which appeared in 1948.

See also

• Confusion and diffusion
• Product cipher
• One-time pad
• Unicity distance