Editing Jefferson disk (section)

== Cryptanalysis ==

The Bazeries cylinder was a relatively strong system at the time (compared to many other systems in use), and Etienne Bazeries, a French military cryptanalyst, is said to have regarded it as indecipherable. The "[[Pers Z S]]" code-breaking group of the German Foreign Office cracked the M-138-A in 1944. However, by that time the Americans had more sophisticated cipher systems in operation.

The French cryptographer Gaetan de Viaris (a.k.a. Marquis Gaetan Henri Leon Viarizio di Lesegno), who is famous for one of the first printing cipher devices (1874), solved the Bazeries cylinder in 1893.<ref>{{cite book |last1=de Viaris |title=L'Art de Déchiffrer les Dépêches Secrètes |date=1893 |publisher=Gauthier-Villars et Fils |location=Paris |pages=50–52, 99–109 |url=https://books.google.com/books?id=mtJtwC7bGxcC |access-date=7 October 2023}}</ref>

One major weakness of the Bazeries cylinder is that the offset from the plaintext letter to the ciphertext letter for the cipher alphabet on each disk will be exactly the same. In the example shown above, this offset is six letters.

For example, if a [[cryptanalyst]] found a message encrypted on the ten-disk Bazeries cylinder described in the example above and has captured their own cylinder, they could decipher the message by entering it on their cylinder and rotating it until they found the message. Still, the number of possible permutations of the disks of the example Bazeries cylinder is {{math|1= 10! = 3,628,800}}. Due to the large size of this number, [[brute force attack|trial and error]] testing of the arrangement of the disks is difficult to perform by hand.