Layout Analysis of Historical Cipher Keys in the DESCRYPT Project – Raphaela Heil

Some archives and libraries hold collections of historical ciphertexts, i.e. documents — handwritten or printed — that were written in some form of code, and whose contents are thus inaccessible to the uninitiated. In order to decipher these documents, it is either necessary to 'crack' the cipher, by applying cryptanalysis methods, or to find a written record, called a cipher key, which establishes the correspondence between plaintext and cipher elements. A first step to facilitate the matching and application of cipher keys to enciphered documents is to identify the relevant regions, which may then be further segmented into individual elements.

In this seminar, we will examine how standard document layout analysis methods perform on the specific case of historical cipher keys, in order to obtain a high-level segmentation. Challenges and opportunities will be demonstrated by using examples from the recently started DESCRYPT project (Riksbankens Jubileumsfond 2025-2032) and its predecessors.

About Raphaela Heil