Pre Twentieth Century
- Al-Khalil ibn Ahmad al-Farahidi: wrote a (now lost) book on cryptography titled the "Book of Cryptographic Messages".
- Al-Kindi, 9th century Arabic polymath and originator of frequency analysis.
- Ibn Wahshiyya: published several cipher alphabets that were used to encrypt magic formulas.
- Ibn 'Adlan: 13th-century cryptographer who made important contributions on the sample size of the frequency analysis.
- Ibn al-Durayhim: gave detailed descriptions of eight cipher systems that discussed substitution ciphers, leading to the earliest suggestion of a "tableau" of the kind that two centuries later became known as the "Vigenère table".
- Ahmad al-Qalqashandi: Author of Subh al-a 'sha, a fourteen volume encyclopedia in Arabic, which included a section on cryptology. The list of ciphers in this work included both substitution and transposition, and for the first time, a cipher with multiple substitutions for each plaintext letter.
- Charles Babbage, UK, 19th century mathematician who, about the time of the Crimean War, secretly developed an effective attack against polyalphabetic substitution ciphers.
- Leone Battista Alberti, polymath/universal genius, inventor of polyalphabetic substitution (more specifically, the Alberti cipher), and what may have been the first mechanical encryption aid.
- Giovanni Battista della Porta, author of a seminal work on cryptanalysis.
- Étienne Bazeries, French, military, considered one of the greatest natural cryptanalysts. Best known for developing the "Bazeries Cylinder" and his influential 1901 text Les Chiffres secrets dévoilés ("Secret ciphers unveiled").
- Julius Caesar, Roman general/politician, has the Caesar cipher is named after him, and a lost work on cryptography by Probus (probably Valerius Probus) is claimed to have covered his use of military cryptography in some detail. It is likely that he did not invent the cipher named after him, as other substitution ciphers were in use well before his time.
- Friedrich Kasiski, author of the first published attack on the Vigenère cipher, now known as the Kasiski test.
- Auguste Kerckhoffs, known for contributing cipher design principles.
- Johannes Trithemius, mystic and first to describe tableaux (tables) for use in polyalphabetic substitution. Wrote an early work on steganography and cryptography generally.
- Philips van Marnix, lord of Sint-Aldegonde, deciphered Spanish messages for William the Silent during the Dutch revolt against the Spanish.
- John Wallis codebreaker for Cromwell and Charles II
- Sir Charles Wheatstone, inventor of the so-called Playfair cipher and general polymath.
Read more about this topic: List Of Cryptographers
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