img
The DECRYPT Project
Decryption of Secret Historical Manuscripts
  • Collection
  • Transcription
  • Decipherment
Go to the ciphers
in the DECODE database

NEWS: To learn more about the decipherment of Mary Stuart’s lost letters go to our Publications!

About Us

Cracking ciphers in a cross-disciplinary team

Thousands of enciphered historical manuscripts are buried in libraries and archives. Examples of such material are diplomatic correspondence and intelligence reports, private letters and diaries as well as manuscripts related to secret societies. The bulk of these historical manuscripts will remain undeciphered unless we can automate the processes involved in decoding them. Our aim is to develop resources and computer-aided tools for decoding of historical source material by using AI and cross-disciplinary research involving computational linguistics, computer vision, cryptology, history, linguistics and philology.

Within the DECRYPT project, we release resources and tools with open access to facilitate research in historical cryptology, allowing collection, analysis and decipherment of historical ciphertexts. Resources are collections of encrypted sources, and historical texts with language models. The tools facilitate the processing of the encrypted sources from transcription to decipherment. We list our resources and tools below, which are described in our scientific publications.

img

Resources and Tools

The DECODE database contains a collection of digitized images of ciphertexts and encryption keys along with metadata information about their provenance, location, transcription, and possible cryptanalysis or commentary. The database enables search and all records in the database are open to the public. HistCorp is a collection of historical corpora and other useful resources and tools for researchers working with historical text. 

We provide tools for transcription and decipherment of historical ciphers using advanced machine learning algorithms. Historical cipher images can be transcribed, i.e. transformed into a computer readable text format with the help of the TranscriptTool. The transcribed ciphertext can be corrected and used as input to CrypTool which assists you in breaking a wide range of historical ciphertexts.  

img
The DECRYPT Portal

PI

img
Beáta
Megyesi

Project leader

Stockholm University

Sweden

Core Team

Participants

Further contributors

The DECRYPT Portal

Our resources and tools are open source and free

We provide a collection of encrypted historical sources, and tools for the automatic analysis and decryption using AI.

Resources
  • DECODE DATABASE

    a collection of thousands of historical ciphertexts and keys

  • HISTCORP

    a collection of historical texts and language models for 16 European languages

Transcription of Ciphers
  • Manual Transcription by CTTS

    An offline crafted to streamline the labor-intensive process of manual transcription

  • TranscripTool

    A tool for semi-automatic transcription using AI

Cryptanalysis
  • CrypTool 2 Transcriber and Solver

    A tool for manual transcription of ciphers (as description)

  • Cryptool Online

    Break (simpler) historical ciphers online

Terms of use

The source code of the platform and tools are being released as open source under the Apache license v.2.0 with the exception of the DECODE database with its special terms and conditions.

img

DECRYPT Publications

2024

  • Beáta Megyesi, Alicia Fornés, Nils Kopal, Benedek Láng, Michelle Waldispühl, Vasily Mikhalev and Bernhard Esslinger. Historical Cryptology. In Bernhard Esslinger (ed), Learning and Experiencing Cryptography with CrypTool and SageMath , Artech, 2024. [fulltext]

2023

  • Láng, B. (2023) Transfer of knowledge in the field of universal language schemes 18th-19th centuries. In Krász, Lilla (ed.): Sciences between Tradition and Innovation – Historical Perspectives/Wissenschaften zwischen Tradition und Innovation – historische Perspektiven. Wien: Praesens Verlag, 2023, 37-55

  • Láng, B. (2023) Valódi és ál-kódfejtések a titkosírások történetében (Real and fake codebreaking in the history of cryptology) In: Bárdos, Dániel; Tuboly, Ádám Tamás (eds.) Emberarcú tudomány : Áltudományok ésösszeesküvés-elméletek szorításában. Budapest, Magyarország : Typotex Kiadó.

  • Lasry, G. (2023) Armand de Bourbon Poly-Homophonic Cipher - 1649. Histocrypt 2023. Published by Linköping Electronic Press. https://doi.org/10.3384/ecp195699

  • Lasry, G., Biermann, N. & Tomokiyo, S. (2023) Deciphering Mary Stuart’s lost letters from 1578-1584, Cryptologia, DOI: 10.1080/01611194.2022.2160677

  • Megyesi, B., Fornés, A., Kopal, N., Láng, B., Waldispühl, M., Mikhalev, V., and Esslinger, B. (2023) Historical Cryptology. Chapter 3 from the book "Learning and Experiencing Cryptography with CrypTool and SageMath", Artech House, December 2023
  • Megyesi, B., Sikora, J., Fornmark, F., Waldispühl, M., Kopal, N., and Mikhalev, V. (2023) Historical Language Models in Cryptanalysis: Case Studies on English and German. In the Proceedings of the 6th International Conference on Historical Cryptology. HistoCrypt 2023. pp. 120-129.
  • Mikhalev, V., Kopal, N., Esslinger, B., Waldispühl, M. Láng,B., and Megyesi B. (2023) What is the Code for the Code? – Historical Cryptology Terminology. In the Proceedings of the 6th International Conference on Historical Cryptology. HistoCrypt 2023. pp. 130-138. 

  • Souibgui, M. A., Biswas, S., Mafla, A., Biten, A. F., Fornés, A., Kessentini, Y., Lladós, J., Gomez, L., & Karatzas, D. (2023). Text-DIAE: A Self-Supervised Degradation Invariant Autoencoder for Text Recognition and Document Enhancement. Proceedings of the AAAI Conference on Artificial Intelligence37(2), 2330-2338. https://doi.org/10.1609/aaai.v37i2.25328
  • Souibgui, M. A., Torras, P., Chen, J.,  and Fornes. A. (2023) An Evaluation of Handwritten Text Recognition Methods for Historical Ciphered Manuscripts. Proceedings of 7th International Workshop on Historical Document Imaging and Processing (HIP).

  • Torras, P.,  Souibgui, M. A., Chen, J., Biswas, S., and Fornes. A. (2023) Segmentation-Free Alignment of Arbitrary Symbol Transcripts to Images. Proceedings of 15th IAPR International Workshop on Graphics Recognition (GREC).

  • Waldispühl, M. Variation and Change. (2023) In Condorelli, M. & Rutkowska, H., The Cambridge Handbook of Historical Orthography. Cambridge: University Press.

2022

2021

  • Chen, J., Souibgui, M.A., Fornés, A., and Megyesi, B. (2021). Unsupervised Alphabet Matching in Historical Encrypted Manuscript Images. In Proceedings of the 4th International Conference on Historical Cryptology. HistoCrypt 2021.
  • Dinnissen J. and Kopal N. (2021). Island Ramanacoil a Bridge too Far. A Dutch Ciphertext from 1674. In Proceedings of the 4th International Conference on Historical CryptologyHistoCrypt 2021.
  • Kopal, N. and Waldispühl, M. (2021). Two Encrypted Diplomatic Letters Sent by Jan Chodkiewicz to Emperor Maximilian II in 1574-1575. In Proceedings of the 4th International Conference on Historical CryptologyHistoCrypt 2021.
  • Láng, B. (2021).The Rohonc code: tracing a historical riddle. 161 pages, accepted for publication by Penn State University Press: April, 2021.
  • Láng, B. (2021). Transfer of knowledge in the field of universal language schemes 18th-19th centuries. In Lilla Krász, ed. Science between tradition and innovation, 2021.
  • Láng, B. (2021)The Rohonc code: tracing a historical riddle. University Park: Penn State University Press, 2021. [https://www.psupress.org/books/titles/978-0-271-09020-7.html]
  • Lasry, G. (2021). Modern Cryptanalysis of Schlüsselgerät 41. In Proceedings of the 4th International Conference on Historical CryptologyHistoCrypt 2021.
  • Lasry, G. (2021). Deciphering a Letter from the French Ambassador in Holland to Louis XIV. In Proceedings of the 4th International Conference on Historical CryptologyHistoCrypt 2021.
  • Leierzopf, E., Kopal, N., Esslinger, B., Lampesberger, H. and Hermann, E. A Massive Machine-Learning Approach For Classical Cipher Type Detection Using Feature Engineering. (2021). In Proceedings of the 4th International Conference on Historical Cryptology. HistoCrypt 2021.
  • Megyesi, B. and Láng, B. (2021) Revealing Secrets from the Past: Studying Historical Ciphers. Abstract to Digitial History in Sweden, Dec. 9-10, 2021, Umeå University, Sweden
  • Megyesi, B. and Tudor, C. (2021)Transcription of Historical Ciphers and Keys. Guidelines, version 2.0. Dept. of Linguistics and Philology, Uppsala University, Sweden. [https://cl.lingfil.uu.se/~bea/publ/transcription-guidelines-v2.pdf]
  • Megyesi, B., Tudor, C., Láng, B, and Lehofer, A. (2021). Key Design in the Early Modern Era in Europe. In Proceedings of the 4th International Conference on Historical Cryptology. HistoCrypt 2021.
  • Pau Torras, Mohamed Ali Souibgui, Jialuo Chen, Alicia Fornés. (2021). A Transcription Is All You Need: Learning to Align through Attention. In Proceedings of the 14th IAPR International Workshop on Graphics Recognition (GREC), 2021. [https://link.springer.com/chapter/10.1007/978-3-030-86198-8_11]

2020

2019

  • Baró A., Chen, J., Fornés, A., and Megyesi, B. (2019) Towards a Generic Unsupervised Method for Transcription of Encoded Manuscripts. In Proceedings of the 3rd International Conference on Digital Access to Textual Cultural Heritage (DATeCH2019), May 2019 Brussels, Belgium. https://cl.lingfil.uu.se/~bea/publ/datech19.pdf
  • Kopal, N. (2019) Cryptanalysis of Homophonic Substitution Ciphers Using Simulated Annealing with Fixed Temperature. In Proceedings of the 2nd International Conference on Historical Cryptology, HistoCrypt 2019, June 23-25, 2019, Mons, Belgium. NEALT Proceedings Series 37, Linköping Electronic Press. [http://www.ep.liu.se/ecp/158/012/ecp19158012.pdf]
  • Láng, B. (2019) Dead ends in breaking an unknown cipher: experiences in the historiography of the Rohonc Codex Proceedings of the 2nd International Conference on Historical Cryptology, HistoCrypt 2019, June 23-26, 2019, Mons, Belgium, Belgium. NEALT Proceedings Series 37, Linköping Electronic Press. [https://ep.liu.se/ecp/158/006/ecp19158006.pdf]
  • Lasry, G. (2019) A Practical Meet-in-the-Middle Attack on SIGABA, Proceedings of the 2nd International Conference on Historical Cryptology, HistoCrypt 2019, June 23-26, 2019, Mons, Belgium, Belgium. NEALT Proceedings Series 37, Linköping Electronic Press. [https://ep.liu.se/ecp/158/005/ecp19158005.pdf]
  • Lasry, G. (2019) Solving a 40-Letter Playfair Challenge with CrypTool 2, Proceedings of the 2nd International Conference on Historical Cryptology, HistoCrypt 2019, June 23-26, 2019, Mons, Belgium. NEALT Proceedings Series 37, Linköping Electronic Press. [https://ep.liu.se/ecp/158/010/ecp19158010.pdf]
  • Lasry, G., Nils Kopal, and Arno Wacker. (2019) "Cryptanalysis of Enigma double indicators with hill climbing." Cryptologia 43.4: 267-292. [https://www.tandfonline.com/doi/abs/10.1080/01611194.2018.1551253]
  • Megyesi, B., Blomqvist, N., and Pettersson, E. (2019) The DECODE Database: Collection of Historical Ciphers and Keys. In Proceedings of the 2nd International Conference on Historical Cryptology. HistoCrypt 2019, June 23-25, 2019, Mons, Belgium. NEALT Proceedings Series 37, Linköping Electronic Press. [https://cl.lingfil.uu.se/~bea/publ/decode-histocrypt-2019.pdf]
  • Pettersson, E. and Megyesi, B. (2019) Matching Keys and Encrypted Manuscripts. In Proceedings of 22nd Nordic Conference on Computational Linguistics, Nodalida 2019. [https://cl.lingfil.uu.se/~bea/publ/keys-nodalida19.pdf]

Theses

  • Anna Lehofer (2024) The Applicability of Hierarchical Clustering to Historical Ciphers. PhD Thesis. Eötvös Loránd University, Budapest, Hungary. DOI: 10.15476/ELTE.2023.248
  • Ingrid Eliasson (2023) Evaluating and Fine-Tuning a Few-Shot Model for Transcription of Historical Ciphers. Master’s thesis in Language Technology, Uppsala University. https://uu.diva-portal.org/smash/get/diva2:1769071/FULLTEXT01.pdf
  • Mohamed Ali Souibgui (2022) Document Image Enhancement and Recognition in Low Resource Scenarios: Application to Ciphers and Handwritten Text. PhD Thesis. December 1, 2022. Computer Vision Center. Universitat Autònoma de Barcelona. Spain.
  • Filip Fornmark (2022) Models, Keys and Cryptanalysis - Evaluating historical statistical language models in cryptanalysis of homophonic substitution ciphers. Bachelor's thesis in Linguistics, Gothenburg University, Sweden.

  • Justyna Sikora (2022) The Influence of Language Models on Decryption of German Historical Ciphers. Master’s thesis in Language Technology, Uppsala University.  http://www.diva-portal.org/smash/record.jsf?pid=diva2%3A1699078&dswid=1999
  • Nikolina Milioni (2022) Evaluating Transcription of Ciphers with Few-Shot Learning. Master’s thesis in Language Technology, Uppsala University. Sweden.
  • Giacomo Magnifico (2021) Lost in Transcription: Evaluating Clustering and Few-Shot Learning for Transcription of Historical Ciphers. Master’s thesis in Language Technology, Uppsala University. Sweden. http://www.diva-portal.org/smash/record.jsf?pid=diva2%3A1616686&dswid=-107
  • Gambardella, Maria-Elena (2021) Cleartext Detection and Language Identification in Ciphers. Master’s thesis in Language Technology, Uppsala University. Sweden. https://www.diva-portal.org/smash/record.jsf?pid=diva2%3A1569329&dswid=4925 
  • Weimann, Niklas (2021) Implementierung und Visualisierung verschiedener kryptografischer Handverfahren und Codes in CrypTool 2 (Engl Title: Implementation and Visualization of different cryptographic hand ciphers and codes in CrypTool 2". Bachelor's thesis in computer science. University of Siegen, Germany, [https://www.cryptool.org/assets/ctp/documents/BA_Weimann.pdf]
  • Addad, Sally (2020) Implementation and Visualization of Steganography Procedures in CrypTool 2. Bachelor's thesis in business informatics. University of Mannheim, [https://www.cryptool.org/assets/ctp/documents/BA_Addad.pdf]
  • Han, Renfei (2020) Using Attention-based Sequence-to-Sequence Neural Networks for Transcription of Historical Cipher Documents. Master’s thesis in Language Technology, Uppsala University, Sweden. [http://www.diva-portal.org/smash/record.jsf?pid=diva2%3A1470446&dswid=4822]
  • Johansson, Kajsa (2019) Transcription of Historical Encrypted Manuscripts: Evaluation of an Automatic Interactive Transcription Tool. Bachelor thesis in Language Technology, Uppsala University, Sweden. [http://uu.diva-portal.org/smash/get/diva2:1323635/FULLTEXT01.pdf]
  • Tudor, Crina (2019) Studies of Cipher Keys from the 16th Century: Transcription, Systematisation and Analysis. Master thesis in Language Technology, Uppsala University, Sweden. [http://uu.diva-portal.org/smash/get/diva2:1369404/FULLTEXT01.pdf]