Substitution Cipher Wheels

"The process of encrypting by substitution may be aided by various devices. A = Z is sufficiently simple as to not require such assistance but more irregular character mappings or mappings that can change mid-stream such as the Alberti cypher is simplified by Alberti's discs. On the inner disc was a mark which could be lined up with a letter on the outer disc as a key, so that if you wanted to encrypt or decrypt a message you only needed to know the correct letter to match the mark to, likewise for decryption. To increase randomness the disc could be turned during an encryption so that a different alphabet is used periodically. This was an early instance of the polyalphabetic cipher, each letter can have different values. One example of this would be to use a key word and index each letter of the plain text to each successive letter of the key: first letter is indexed to C, second to A, third to T, fourth to C... and so on. When encrypting an interval of rotation can be predetermined by those reading and writing the ciphertext, adding a shift based on the letters in a secret shared keyword.

Albreti (Di Cifres) describes these discs as being made from copper but other examples, such as Porta (1563) show the wheel/disc as what appears to be an engraved, presumably wooden, object. I have chosen to use engraving to make my discs due to access of materials and precision of the tools available."

- Kevin Baun, An Introduction to Historical Cryptography, 2021

Alberti's cipher disk (De Cifris, 1467, from Biblioteca Apostolica Vaticana MS Chigi M II 49, vol. 35).

Silvestri's cipher disk. Opus Novum. 1526.

Porta, page 73, 1563, De Furtivis Literarum notis, vulgo de Ziferis libri IIII

Porta, page 79, 1563, De Furtivis Literarum notis, vulgo de Ziferis libri IIII

Porta, page 83, 1563, De Furtivis Literarum notis, vulgo de Ziferis libri IIII

Baun, Functional reimagining of the one of Porta's wheels.

Baun, My interpertation of the 1467 Alberti wheel incorporating a Trithemian substitution cipher at the top and design elements inspired by the Porta wheels.

Baun, Two cipher wheels of my creation. These, like the one above, are based on the Alberti disc design and incorporate design elements from Porta's wheels. The knot and crab designs on the moblis represent two baronies in Atlantia. The intention is to (eventually) make one for each barony and distribute across the kingdom.

Baun, A wheel of my own design that uses runes as the substitution value of the moblis disk.