Not Disk but System: The Meaning of "formula" in Alberti's De Cifris

Abstract

The “formula” given by Alberti in his book named De Cifris is acknowledged as physical hardware, namely the cipher disk. A comprehensive analysis of the explanation of “formula” in Alberti’s work and subsequent scholars’ learning of its methods reveals that the previous understanding is not Alberti’s original idea. Alberti's “formula” is not only the cipher disk but also a cryptography system with multiple mapping relationships and multi-layer mapping relationships. Therefore, Albert’s invention of the encryption method is the application of mathematical ideas and methods.