Combinatorial Wheels and Movable Alphabets: from Ramon Llull to Leon Battista Alberti

Abstract

This article reconstructs an alternative pre-history of late medieval cryptography by situating letterbased cipher devices within a broader tradition of combinatorial wheels, volvelles, and alphabetic diagrams. Starting from Ramon Llull’s Ars Magna, it analyses how rotating systems of letters functioned as engines of combination designed to generate knowledge, and traces how similar visual–mechanical principles reappeared in divinatory practices (onomancy, sortes literature, and divinatory volvelles), ritual magic, and mnemotechnics. The core cryptographic contribution lies in the discussion of alphabetic wheels that no longer encode divine attributes but human secrets, culminating in Leon Battista Alberti’s polyalphabetic cipher disk and Giovanni Fontana’s hybrid mnemonic–cipher machines. By comparing these devices structurally rather than doctrinally, the article argues that medieval cryptography emerged within a shared manuscript culture of movable alphabets, permutation, and controlled randomness. While direct lines of influence can rarely be demonstrated, the persistence of concentric letter wheels across divination, magic, mnemotechnics, and cryptology suggests a common visual and combinatorial grammar that shaped the earliest mechanical thinking about encryption.