The aim of this paper is to show that the tradition related to alphabets upon the fingers, which had its origin in both scriptura digitorum and ars memoriae, had new applications in the 17th-Century Linguistics thanks to new approaches within the field: teaching language to the deaf and its use as a secret form of communication, due to the development of cryptography. Taking into account the importance of language of gestures in this context, finger spellings are presented as cryptographic codes by Wilkins (1694 [1641]), Bulwer (1644) and Caramuel (1665 [1657]), who also defended the idea of gestures as universal characters.