Caratteristiche strutturali di cifrari monoalfabetici italiani nei secoli XV e XVI
This paper analyzes some structural characteristics of Italian monoalphabetical code books from the 14th and 15th centuries. Usually, each cipher key represents the symbols and the principal rules of a different cipher system. First, we present the general parts of the tables, then we examine these parts in detail collecting their various safety elements. For the evaluation and description of the security system of each code book a scale is presented which has two main aspects: the measures of substitution of the alphabetical letters by ciphers, and the numbers and the nature of the safety elements. In our corpus, in addition to complete cipher keys, there is also a reconstructed cipher obtained by the parsing of coded and decoded texts of Maffeo di Treviglio.