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.
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