Function vernam_encrypt

Vernam Cipher The Vernam cipher is a symmetric stream cipher where plaintext is combined with a random or pseudorandom stream of data (the key) of the same length. This implementation uses the alphabet A-Z with modular arithmetic. # Algorithm For encryption: C = (P + K) mod 26 For decryption: P = (C - K) mod 26 Where P is plaintext, K is key, and C is ciphertext (all converted to 0-25 range) E

(plaintext: &str, key: &str)