Solving Classical Ciphers with CrypTool 2

Nils Kopal
Applied Information Security, University of Kassel, Kassel, Germany

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Ingår i: Proceedings of the 1st International Conference on Historical Cryptology HistoCrypt 2018

Linköping Electronic Conference Proceedings 149:10, s. 29-38

NEALT Proceedings Series 34:10, p. 29-38

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Publicerad: 2018-06-13

ISBN: 978-91-7685-252-1

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


The difficulty of solving classical ciphers varies between very easy and very hard. For example, monoalphabetic substitution ciphers can be solved easily by hand. More complex ciphers like the polyalphabetic Vigenère cipher, are harder to solve and the solution by hand takes much more time. Machine ciphers like the Enigma rotor machine, are nearly impossible to be solved only by hand. To support researchers, cryptanalysts, and historians analyzing ciphers, the open-source software CrypTool 2 (CT2) was implemented. It contains a broad set of tools and methods to automate the cryptanalysis of different (classical and modern) ciphers. In this paper, we present a step-by-step approach for analyzing classical ciphers and breaking these with the help of the tools in CT2. The primary goals of this paper are: (1) Introduce historians and non-computer scientists to classical encryption, (2) give an introduction to CT2, enabling them to break ciphers by their own, and (3) present our future plans for CT2 with respect to (automatic) cryptanalysis of classical ciphers. This paper does not describe the used analysis methods in detail, but gives the according references.


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Nada Aldarrab, Kevin Knight, and Beata Megyesi. 2018. The Borg.lat.898 Cipher. http://stp.lingfil.uu.se/~bea/borg/.

Michael J Cowan. 2008. Breaking short playfair ciphers with the simulated annealing algorithm. Cryptologia, 32(1):71–83.

Daily Mail Reporter. 2010. CIA codebreaker reveals 147-year-old Civil War message about the Confederate army’s desperation. https://dailym.ai/2JkVFCu.

Amrapali Dhavare, Richard M Low, and Mark Stamp. 2013. Efficient cryptanalysis of homophonic substitution ciphers. Cryptologia, 37(3):250–281.

William S Forsyth and Reihaneh Safavi-Naini. 1993. Automated cryptanalysis of substitution ciphers. Cryptologia, 17(4):407–418.

William Frederick Friedman. 1987. The index of coincidence and its applications in cryptanalysis. Aegean Park Press California.

James J Gillogly. 1995. Ciphertext-Only Cryptanalysis of Enigma. Cryptologia, 19(4):405–413.

Nils Kopal, Olga Kieselmann, ArnoWacker, and Bernhard Esslinger. 2014. CrypTool 2.0. Datenschutz und Datensicherheit-DuD, 38(10):701–708.

Nils Kopal. 2018. Secure Volunteer Computing for Distributed Cryptanalysis. http://www.upress.uni-kassel.de/katalog/abstract.php?978-3-7376-0426-0.

George Lasry, Nils Kopal, and Arno Wacker. 2016a. Automated Known-Plaintext Cryptanalysis of Short Hagelin M-209 Messages. Cryptologia, 40(1):49–69.

George Lasry, Nils Kopal, and Arno Wacker. 2016b. Ciphertext-only cryptanalysis of Hagelin M-209 pins and lugs. Cryptologia, 40(2):141–176.

George Lasry, Nils Kopal, and Arno Wacker. 2016c. Cryptanalysis of columnar transposition cipher with long keys. Cryptologia, 40(4):374–398.

George Lasry, Ingo Niebel, Nils Kopal, and Arno Wacker. 2017. Deciphering ADFGVX messages from the Eastern Front of World War I. Cryptologia, 41(2):101–136.

George Lasry. 2018. A Methodology for the Cryptanalysis of Classical Ciphers with Search Metaheuristics. kassel university press GmbH.

Thomas G Mahon and James Gillogly. 2008. Decoding the IRA. Mercier Press Ltd.

Beata Megyesi, Kevin Knight, and Nada Aldarrab. 2017. DECODE – Automatic Decryption of Historical Manuscripts. http://stp.lingfil.uu.se/~bea/decode/.

Phil Pilcrow. 2018. CryptoCrack. http://www.cryptoprograms.com/.

Tobias Schrödel. 2008. Breaking Short Vigenere Ciphers. Cryptologia, 32(4):334–347.

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