Implementation of Hill Cipher, Luhn Algorithm, and RSA Algorithm
(I) Hill Cipher is a polyalphabetic cipher created by extending the Affine cipher, using linear algebra and modular arithmetic via a numeric matrix that serves as an encryption and decryption key.
Encryption: E(K, P) = (K * P) mod 26
Decryption: D(K, C) = (K-1 * C) mod 26