Secure Volunteer Computing for Distributed Cryptanalysis

Zugleich: Dissertation, Universität Kassel, 201

Two Encrypted Diplomatic Letters Sent by Jan Chodkiewicz to Emperor Maximilian II in 1574-1575

This paper presents the work on two encrypted diplomatic letters sent by the Lithuanian nobleman Jan Chodkiewicz to emperor Maximilian II in 1574 and 1575. It describes the decipherment process as well as the content and the context of the letters. Furthermore, it provides linguistic aspects of the used plaintext language. It continues our previous work on Habsburg ciphers where we analyzed and contextualized three diplomatic letters sent by Maximilian II. All presented and analyzed letters relate to the Polish-Lithuanian election in 1575, where Maximilian II, his son Ernst, and his brother Ferdinand were amongst the candidates. The deciphered German plaintexts of all five letters can be accessed via the DECODE database, a storage for historical encrypted manuscripts, which is maintained by members of the DECRYPT project

Island Ramanacoil a Bridge too Far. A Dutch Ciphertext from 1674

The deciphered Ramanacoil ciphertext reveals two Dutch East India Company letters, from 1674 that are, in retrospect, already known in the National Archives as plaintext letters. The letters are written in Dutch. We have been able to relate them. The first letter, from Van Goens senior from Sri Lanka to the Lords Seventeen in The Netherlands, was most important to the sender. He sent his personal secretary Leeuwenson overland with the ciphertext in his pocket and its key in his head. And with additional oral information that had to be delivered in person. Van Goens senior requested to conquer the whole of Sri Lanka, the island Ramanacoil and coastal area around it along with 1,000 more soldiers. This paper shows that by sending Leeuwenson, Van Goens senior wanted to repeat his most successful ‘Vertoog’ from 1655. Substantiate his strategic goals and get approval for them from the Lords Seventeen. In 1655 he got a ‘Go!’ and twenty years later in 1675 he got a ‘No!’. The zeitgeist of expansion had changed. Ramanacoil was a bridge too far

A Massive Machine-Learning Approach For Classical Cipher Type Detection Using Feature Engineering

Cryptanalysis of enciphered documents typically starts with identifying the cipher type. A large number of encrypted historical documents exists, whose decryption can potentially increase the knowledge of historical events. This paper investigates whether machine learning can support the cipher type classification task when only ciphertexts are given. A selection of engineered features for historical ciphertexts and various machine-learning classifiers have been applied for 56 different cipher types specified by the American Cryptogram Association. Different neuronal network models were empirically evaluated. Our best-performing model achieved an accuracy of 80.24% which improves the current state of the art by 37%. Accuracy is calculated by dividing the total number of samples by the number of true positive predictions. The software-suite is published under the name ”Neural Cipher Identifier (NCID)”

Evaluating GPT-4’s Proficiency in Addressing Cryptography Examinations

In the rapidly advancing domain of artificial intelligence, ChatGPT, powered by the GPT-4 model, has emerged as a state-of-the-art interactive agent, exhibiting substantial capabilities across various domains. This paper aims to assess the efficacy of GPT-4 in addressing and solving problems found within cryptographic examinations. We devised a multi-faceted methodology, presenting the model with a series of cryptographic questions of varying complexities derived from real academic examinations. Our evaluation encompasses both classical and modern cryptographic challenges, focusing on the model\u27s ability to understand, interpret, and generate correct solutions while discerning its limitations. The model was challenged with a spectrum of cryptographic tasks, earning 201 out of 208 points by solving fundamental queries inspired by an oral exam, 80.5 out of 90 points on a written Crypto 1 exam, and 287 out of 385 points on advanced exercises from the Crypto 2 course. The results demonstrate that while GPT-4 shows significant promise in grasping fundamental cryptographic concepts and techniques, certain intricate problems necessitate domain-specific knowledge that may sometimes lie beyond the model\u27s general training. Insights from this study can provide educators, researchers, and examiners with a deeper understanding of how cutting-edge AI models can be both an asset and a potential concern in academic settings related to cryptology. To enhance the clarity and coherence of our work, we utilized ChatGPT-4 to help us in formulating sentences in this paper

Evaluating Deep Learning Techniques for Known-Plaintext Attacks on the Complete Columnar Transposition Cipher

This paper examines whether deep neural networks (DNN) can learn knownplaintext attacks on plaintext-ciphertextpairs, that were created by encrypting with complete columnar transposition. We propose a new algorithm that extends pure DNN-based prediction with additional post-processing steps to further enhance key prediction quality. Our approach is easily extensible and currently supports key lengths from 2 to 20 characters. Each key length has been empirically evaluated with plain-/ciphertextpairs of different lengths. For plain- and ciphertexts with a length of five times the key length, our algorithm achieves a success rate of 96% which is, to the best of our knowledge, a new state of the art on deep-learning-based known-plaintext attacks against columnar transposition

Deciphering three diplomatic letters sent by Maximilian II in 1575

This article presents three newly rediscovered encrypted Habsburg letters that were sent by Maximilian II to his Polish delegates in 1575. We describe the process of deciphering and the principles and peculiarities of the cipher from a cryptographic perspective. Furthermore, content and historical and linguistic context of the letters are explained. The records are held at the Österreichisches Haus-, Hof- und Staatsarchiv and were collected and deciphered in the context of the interdisciplinary and international research project “DECRYPT – Decryption of historical manuscripts”. For cryptanalysis the open-source e-learning program CrypTool 2 was used. The article is the result of a joint effort of a computer scientist and a historical linguist

Decipherment of a German encrypted letter sent from Sigismund Heusner von Wandersleben to Axel Oxenstierna in 1637

We present our work on an encrypted letter from the Thirty Years’ War written by the ally of the Swedish Empire, Sigismund Heusner von Wandersleben in 1637 and sent from Kassel to the Swedish High Lord Chancellor Axel Oxenstierna. We describe our analysis of the ciphertext including information on the cipher type, the process of cryptanalysis and challenges for the decipherment. We include the edition of the letter in the current state of decipherment and summarize its content

Send someone to finish Fredenburgh’s works. A Dutch ciphertext (1689) from Suriname

A ciphertext without its corresponding key was found in the archives from the Dutch colony Suriname, in the National Archives at The Hague. We were able to decrypt it through cryptanalysis and with the use of CrypTool2. The revealed plaintext contains a letter with military sensitive information and the name of Fredenburgh, who served as Governor ad interim from 1688 to 1689. It was sent in May 1689 by Governor Van Scharphuijsen to his directors in Amsterdam. Since 1689, the Society of Suriname (SvS) used ciphers for its militarily sensitive information. Ciphertext U3 was sent during the Nine Years’ War (1688-1697) when the Dutch were at war with the French. The letter was encrypted as a precaution against possible interception by the (French) enemy

Decipherment of an Encrypted Letter from 1724 Found in UCL Special Collections’ Brougham Archive

This paper shows the decipherment of a 1724 encrypted letter, discovered recently in the Brougham Archive at University College London (UCL) Special Collections. The letter’s content hints at political intrigue and possibly relates to the Jacobite movement during George I’s reign in Great Britain. However, as all individuals mentioned in the letter are referred to bycode names, except for Madame de Prie, their true identities remain unknown to the authors. Therefore, any connection to the Jacobites remains speculative. The paper covers the cipher’s security, historical context, and unresolved inquiries surrounding the letter