ABSTRACTChaocipher is a manual encryption method designed by John F. Byrne in 1918. Until he passed away in 1960, Byrne fervently believed that his cipher system was unbreakable, regardless of the amount of material available to a cryptanalyst. For several decades, he tried (unsuccessfully), to propose the Chaocipher to government agencies. In 1953, he exposed his Chaocipher in his autobiography, Silent Years, providing several examples of texts encrypted with Chaocipher as challenges, but without divulging the inner workings of the cipher. Those were made public only in 2010, when Byrne’s family donated the entire corpus of Chaocipher papers to the National Cryptologic Museum (NCM) in Fort Meade.A known-plaintext method for recovering the key settings, given sufficient matching plaintext and ciphertext, was published in 2010. However, to date, no method for the cryptanalysis of a single ciphertext-only Chaocipher message has been proposed, nor for the cryptanalysis of short messages “in-depth,” i.e., mul...
['George Lasry', 'Moshe Rubin', 'Nils Kopal', 'Arno Wacker']
Cryptanalysis of Chaocipher and solution of Exhibit 6