Can musical encryption be both? A survey of music-based ciphers

Abstract The purpose of this article is to analyze the characteristics of a range of music-based ciphers (from the fifteenth to twentieth centuries) with respect to their intended goals and actual outcomes. Historically, the practitioners of music-based ciphers generally fall into one of two distinct groups: composers and cryptographers. The primary goal of the composers was to create music that embedded extra-musical content by means of musico-alphabetic correspondences. The cryptographers were generally interested in presenting many varieties of cryptographic methods of which ciphers incorporating musical notes were a very small part. The systems used by the former were usually so superficial they should not really be considered encryption; whereas the systems used by the latter were so mechanical that most would not consider the results to be music. Musical encryption can rarely be both because the attributes needed for convincing musicality and strong encryption are not mutually conducive. However, after examining these music-based cryptosystems in detail, I will consider what criteria might be necessary to create a reasonably secure cipher which produces a normatively-musical output and apply these in the form of an original music-based cipher. For most of the ciphers, interactive web applications have been developed which render plaintext into enciphered melodies.