4. Theory and practice of cryptography in early modern Europe

Abstract

We would not have to waste a lot of words on the pre-1400 history of cryptography if it were not for the Arabs. Most of the cryptographic methods in Latin and later in national languages remained on the level of simple substitutions until the late medieval centuries. In the beginning only vowels were substituted for signs that were made up of dots and then graphic symbols. Later every single letter of the plain text was replaced by a corresponding numeral, letter or symbol. That means that, as the ciphertext was being constructed, the user took the letters from the plain text one by one and wrote their corresponding symbol down in the secret (or rather encrypted) text. This method assigned one single string of symbols, numerals or letters to the original alphabet, in other words, it used one single code alphabet to encipher the plain text, and therefore this encryption is called the monoalphabetic cipher.