A large number of enciphered documents survived from early modern Hungary. This area was a particularly fertile territory where cryptographic methods proliferated, because a large portion of the population was living in the frontier zone, and participated (or was forced to participate) in the network of the information flow. A quantitative analysis of sixteenth-century to seventeenth-century Hungarian ciphers (300 cipher keys and 1,600 partly or entirely enciphered letters) reveals that besides the dominance of diplomatic use of cryptography, there was a presence of ''private'' applications as well. The monograph reconstructs the main reasons and goals why historical actors chose to use ciphers in a diplomatic letter, a military order, a diary or a private letter, what they decided to encrypt, and how they perceived the dangers threatening their messages.