Abstract

Rémi Géraud-Stewart and David Naccache have recently discovered historical documents from the late 19th century, written by Major H.D. Josse of the French Army, that describe a proposal for a new cipher. In our paper, we provide an in-depth analysis of the cipher and a revised formal description of the cipher based on the examples given by Josse. We also present classes of cryptologically equivalent keys, and a possible attack based on ciphertext isomorphs, that can be implemented with only pen-and-paper. We also describe a new ciphertext-only stochastic attack, based on simulated annealing, that can recover the key and the plaintext from ciphertexts with only 75 letters. We are planning to implement the cipher in CrypTool 2, an e-learning platform for cryptography.

摘要

Rémi Géraud-Stewart 和 David Naccache 最近发现了 19 世纪末的历史文件，由法国陆军少校 HD Josse 撰写，其中描述了一种新密码的提议。在我们的论文中，我们提供了对密码的深入分析，并根据 Josse 给出的示例对密码进行了修订的正式描述。我们还介绍了加密等效密钥的类别，以及基于密文同构的可能攻击，仅用纸笔即可实现。我们还描述了一种新的纯密文随机攻击，它基于模拟退火，可以从只有 75 个字母的密文中恢复密钥和明文。我们计划在密码学电子学习平台 CrypTool 2 中实施密码。