Számítástudomány, információtudomány és bioinformatika
We give an overview of the development of European historical cipher keys originating
from early Modern times. We describe the nature and the structure of the keys with
a special focus on the nomenclatures. We analyze what was encoded and how and take
into account chronological and regional differences. The study is based on the analysis
of over 1,600 cipher keys, collected from archives and libraries in 10 European countries.
We show that historical cipher keys evolved over time and became more secure, shown
by the symbol set used for encoding, the code length and the code types presented
in the key, the size of the nomenclature, as well as the diversity and complexity
of linguistic entities that are chosen to be encoded.
