CaesarChiffre

CaesarChiffre, commonly known as the Caesar cipher, is one of the simplest and oldest cryptographic techniques. It is a substitution cipher that replaces each letter of the plaintext with the letter a fixed number of positions later in the alphabet. The method is attributed to Julius Caesar, who reportedly used it to protect messages in his military campaigns. It serves as a classic example of a shift cipher and is often taught as an introduction to cryptography.

Mechanism and variations: The cipher operates on a alphabet of 26 letters. A chosen shift value k between 1 and 25 determines the transformation: each letter p is replaced by the letter (p + k) mod 26. Decryption uses the inverse shift (c - k) mod 26. In practice, case is usually ignored and non-letter characters are left unchanged. The Caesar cipher is a specific case of the broader class of monoalphabetic substitution ciphers and, more generally, a simple instance of the affine cipher when the multiplier a equals 1.

Security and limitations: The cipher offers no real security by modern standards. Its output preserves most letter frequencies, and only 25 possible shifts exist, making brute-force and frequency-based attacks trivial. It is widely used today as an educational tool to demonstrate basic cryptographic concepts rather than for any practical confidentiality.

Variants and legacy: A related family is the ROT-n family, with ROT13 being a fixed shift of 13. The Caesar cipher is often discussed in historical contexts and puzzles, highlighting the evolution from simple to more complex cryptographic methods.