Hill Cipher (encryption) Apr 2026

: To reverse the process, the recipient must multiply the ciphertext vector by the inverse of the key matrix. Key Constraints & Security

The Hill Cipher, introduced by Lester S. Hill in 1929, is a polygraphic substitution cipher that applies linear algebra to cryptography. Unlike simple substitution ciphers that replace one letter at a time, the Hill Cipher encrypts groups of letters simultaneously using matrix multiplication. How It Works Hill Cipher (Encryption)

letters is converted into a number (e.g., A=0, B=1... Z=25). : This -component vector is multiplied by an key matrix. : To reverse the process, the recipient must

: The resulting values are taken modulo 26 (or the size of the character set) to stay within the alphabet range. Unlike simple substitution ciphers that replace one letter

While historically significant for being the first cipher practical for blocks larger than three symbols, it has notable limitations: Hill Cipher Oracle Attack - LACTF2023 - crypto/hill-easy