Conference article

Cryptanalysis of an Early 20th Century Encrypted Journal

Tony Gaffney
Private Scholar

Klaus Schmeh
Freelanced Journalist

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Published in: Proceedings of the 2nd International Conference on Historical Cryptology, HistoCrypt 2019, June 23-26, 2019, Mons, Belgium

Linköping Electronic Conference Proceedings 158:11, p. 97-105

NEALT Proceedings Series 37:11, p. 97-105

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Published: 2019-06-12

ISBN: 978-91-7685-087-9

ISSN: 1650-3686 (print), 1650-3740 (online)


Ernest Rinzi (1836-1909), a Londonbased jeweler, goldsmith and miniaturist, left behind an encrypted journal, which went unsolved until 2017. Dozens of artistically designed illustrations, which interact with text written in tiny letters, make this 175 pages journal one of the most outstanding cryptograms in existence. In 2017 one of the two authors of this paper brought Rinzi’s journal to the attention of a wider audience, which led to the other author examining and breaking the encryption. The cipher Rinzi used proved a monoalphabetic substitution cipher (MASC) that replaces letters and numbers. The cryptanalysis work was complicated by the unusual and hard-toread miniature writing.


encrypted diary encrypted journal monoalphabetic substitution cryptanalysis Ernest Rinzi


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