Deciphering Historical Syllabic Ciphers

Abstract

Historical ciphers with syllabic elements are significantly more challenging for cryptanalysis than regular homophonic ciphers. We present here a novel computerized technique which recovers significant parts of the keys, allowing for the remaining parts to be manually completed. We solved several previously undeciphered French, Spanish, and Italian syllabic ciphers, and we also evaluated the performance of this method against a series of additional historical syllabic ciphers.