Early Mechanical Cryptography and Binary Keying or The Possible Impact of the Damm Brothers on Leibniz’s Machina Deciphratoria

Abstract

Mechanical cipher machines employing binary keying elements became widespread in the first half of the twentieth century. This paper examines the origins of binary keying in mechanical cryptography, motivated by Gottfried Wilhelm Leibniz’s early work on binary arithmetic, his calculating machine (Machina Arithmetica), and his documented interest in cryptology. By analysing Leibniz’s surviving descriptions of a proposed cipher machine (Machina Deciphratoria), a reconstruction of this machine from 2012, and early cipher machines developed by Arvid Damm, we found no evidence that binary keying was intended in Leibniz’s cryptographic ideas. Instead, binary keying appeared as a distinctly twentieth-century development. The article highlights the possibility that reconstructions — when based on sparse sources — may unintentionally incorporate later design concepts into the reconstructed device, so that a historical device could be retroactively influenced by a modern idea.