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. It is one of the foundational treatments of modern cryptography. It is also a proof that all theoretically unbreakable ciphers must have the same requirements as the one-time pad.
Shannon published an earlier version of this research in the classified report A Mathematical Theory of Cryptography, Memorandum MM 45-110-02, Sept. 1, 1945, Bell Laboratories. This classified report also precedes the publication of his "A Mathematical Theory of Communication", which appeared in 1948.
