Nomenclator (cryptology)
A nomenclator is an encryption system based on a ciphertext alphabet and a number of code words .
The procedure is actually somewhat more secure than simple monoalphabetic encryption , but it is not really protected against deciphering , because the majority of the message can be deciphered by frequency analysis and cryptanalysts can find out the remaining words from the context of the text. Compared to the simplest procedures such as the Caesar alphabet, the somewhat faster handling and the compact size for later procedures should be mentioned.
One of the most famous nomenclators was used by Maria Stuart . The code was broken by Thomas Phelippes , who was then working for Francis Walsingham , and resulted in the execution of Maria Stuart.
From a technical point of view, it is an early combined encryption system, although still without a key itself and using similar components:
- a code alphabet, in the simplest case Caesar , for example , more complex, for example, with homophones , in which a plaintext letter can be translated into several ciphertext letters.
- often a similar “alphabet” for numbers
- some code words, summarized in lists, for frequently used or particularly important or telltale parts of the text, such as people, places, days of the week (...)
- often a few zeros or blenders, words and single characters without meaning to the confusion of an unauthorized decipherer
The compilation of a nomenclator initially only comprised one page. The application was by no means always continuous, in some cases text parts written in plain text were combined with encrypted, "secret" parts. This labor-saving approach of course also saved unauthorized decryptors a lot of effort.
Painted “special characters” that were also used at the beginning were dispensed with in the course of development for reasons of legibility. From the early nomenclators, the well-known one- and two-part code books , previously often used in the diplomatic service or for telegraphy, developed . The size of the code word lists in these “dictionaries” increased accordingly to several thousand elements, and often more or less effective over-coding was then included.