in order to smooth any irregularities that might indicate the hidden words. The recipient of the message must possess an identical grille. Copies of grilles are cut from an original template, but many different patterns could be made for one-to-one correspondence. The grille can be placed in four positions – face up and face down, upright and reversed – which increases the number of possible cell positions fourfold. In practice it can be difficult to construct an innocent message around a hidden text. Stilted language draws attention to itself and the purpose of the Cardan grille is to create a message “without suspicion” in the words of Francis Bacon. But the task was easier for Cardano, because 16th century spelling was not standardised and left much room for contractions and adornments of penmanship. Detection of messages When executed badly, a Cardan message stands out because of stilted language and uneven writing. An analyst may attempt to reconstruct the grille when there are several examples of suspect messages from a correspondent. When executed well, a Cardan message can be difficult to spot. Even when an analyst suspects the presence of a message, an innocent letter can contain apparently hidden text. So, in practice, the only solution is to obtain the grille itself. Disadvantages The method is slow and requires literary skill. Above all, any physical cipher device is subject to loss, theft and seizure; so to lose one grille is to lose all secret correspondence constructed with that grille. Possession of a grille may be incriminating. The Cardan grille, in its original form, is of more literary than cryptographic interest. For example, controversy surrounds the Voynich manuscript which could be a 16th-century fake cipher text, possibly constructed with a Cardan grille which was used to generate pseudo-random nonsense from a pre-existing text. See also Grille (cryptography) References David Kahn, The Codebreakers — The Comprehensive History of Secret Communication from Ancient Times to the Internet, 1996, . External links https://web.archive.org/web/20111005155213/http://www2.si.umich.edu/spies/methods-mask.html Classical cryptography