Caesar cipher

A substitution cipher that shifts each plaintext letter by a fixed number of positions in the alphabet, wrapping from the end to the beginning.

Modular arithmetic: Arithmetic in which numbers wrap around after reaching a fixed modulus. The alphabet’s wraparound makes each letter shift an addition modulo 26.
Julius Caesar: Roman military and political leader who became dictator and was assassinated in 44 BCE. Ancient accounts associate Caesar with using letter shifts for confidential correspondence.
Atbash: A monoalphabetic substitution cipher that maps the first alphabet letter to the last, the second to the penultimate, and so on. Unlike a selectable shift, Atbash uses a fixed reversed-alphabet mapping.
Cryptography education: The teaching of cryptographic ideas, methods, and security principles. The cipher makes keys, encryption, decryption, and brute-force attacks easy to demonstrate.
Substitution cipher: A cipher that encrypts by replacing plaintext symbols with other symbols according to a rule. The Caesar cipher is the simplest fixed-shift member of this cipher family.
Suetonius: Roman biographer whose work Lives of the Caesars describes emperors and their lives. His account preserves the best-known ancient description of Caesar’s shifted-letter messages.
Affine cipher: A monoalphabetic substitution cipher that transforms alphabet positions using multiplication and addition modulo the alphabet size. It generalizes the Caesar shift by adding a multiplicative key as well as an offset.
Geocaching puzzle: A puzzle used in geocaching that requires solving a clue to locate a cache. A Caesar shift can conceal coordinates or hints in recreational puzzle clues.
Cryptanalysis: The study of analyzing information systems to recover hidden information or defeat their security. Its tiny key space and preserved letter patterns make cryptanalysis straightforward.
De vita Caesarum: Suetonius’s collection of biographies of Julius Caesar and the first eleven Roman emperors. Its biography of Julius Caesar records a shift cipher attributed to him.

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Commentarii de Bello GallicoCompared with: Its familiar name reflects Caesar’s later popular image, though the work does not describe the cipher.