Caesar cipher, also known as shift cipher, is one of the simplest and most widely used encryption techniques. It is a type of substitution cipher in which one letter in the original text is replaced by another letter found N positions later in the alphabet.
| Encryption function | Key | Decryption function |
|---|---|---|
| \[E_{(a,b)}(M)=(aM+b)\bmod N \begin{cases}a,b < N\end{cases} \] | \[K(a,b) \] | \[D_{(a,b)}(M) = (\frac{M - b}{a})\bmod N \begin{cases}a,b < N\end{cases}\] |