Peirce’s Contribution to American Cryptography

In an undated letter, Peirce claims that he can make a machine that will automatically encrypt and decrypt messages, an astonishing claim considering the state of American science during his time. In two undated manuscripts, Peirce actually describes a cryptosystem, a system for encrypting and decrypting, suggesting the use of arithmetical transformations and binary notation. The relationship between the manuscripts and the letter are discussed in the paper. The paper also describes Peirce’s cryptosystem, places it in its historical context and assesses its comparative value. The paper ends with speculations on whether Peirce could really have built the machine. Considering that he understood the relationship between electricity, binary arithmetic, and Boolean logic, and was familiar with the experiences on the logical machines of his time, the paper concludes that Peirce had all the knowledge necessary to build such a machine.