Cryptography

**Cryptography**, also known as **Cryptology**, is the practice and study of techniques for converting information into a form for secure communication or storage in the face of a known or potential adversary.

Due to the covert, sensitive or hidden nature of certain subjects concerning them, various aspects of cryptography are utilized on both magic and science sides.

## Etymology

The prefix *crypto-*, present in both cryptography and cryptology, is derived from the Greek kryptos/kruptós/κρυπτός (meaning "hidden" or "secret"). For the respective suffixes, *-graphy* derives from *-graphia*/gráphō/γράφω (meaning "writing"), and *-logy* derives from -λογία/*-logia* ("study/account of").

Two terms in Japanese that can be used to refer to many subjects within the field of cryptography/cryptology are **angō** (暗号, ***angō***? used for "code", "cipher", "encryption", "cryptography" etc) and **kaidoku** (解読, ***kaidoku***? used for "decode/decoding", "deciphering", "decrypt/decrypting" etc).

## Principles

There are various methods of encryption and different types of cipher. Two examples of basic cipher types are a transposition cipher (one of which is utilized with the scytale), where the positions of characters are moved to produce a different permutation of a text's characters, and a substitution cipher (of which, the Caesar cipher is a basic example), where characters are substituted for different characters. In modern times, the advance of science has given rise to new methods of encryption, including applications of random number generation and properties of quantum mechanics (applications of the latter, encryption and otherwise, being referred to as quantum cryptography).

The **Caesar cipher** (カエサル式暗号, *Kaesaru-shiki Angō*?), named after and used by the famous Roman general Julius Caesar in private correspondence, is a basic substitution cipher which often used as an initial foundation leading into more complex encryptions. With it, the letters in the text are substituted with the respective letters a set number of places from them along the alphabet, forwards or backwards.

There are various tools which have been used to support cryptographic processes, from simple mechanical devices to modern computers. A very early example used in ancient Greece is the **scytale** (スキュタレー式, *Sukyutarē-shiki*?), a cylinder around which a strap of single letters is wrapped. Using a type of transposition cipher, when wrapped around the sideways cylinder vertically, the letters on the strap line up to spell out the intended message horizontally, one which isn't apparent from the order of the letters on the strap when it is unwrapped.

One variant of cryptography is steganography, which involves concealing a hidden message within another message or an object. Rather than just protecting the contents of a message, steganography also involves concealing the fact that a secret message is being sent.

Given the use of codes in the magic side, large counter-magical organizations such as Necessarius may have decoding specialists among their ranks, such as Orsola Aquinas and Sherry Cromwell, the latter specializing in codes hidden in paintings. The position of Cancellarius in the Roman Catholic Church, once held by Aureolus Izzard, was one said to be involved in decoding witchcraft and finding countermeasures.