Alberti Cipher
The Alberti Cipher, invented by Leon Battista Alberti in the 15th century, is widely regarded as the first polyalphabetic cipher. It introduced the revolutionary concept of using multiple cipher alphabets to encrypt a message, rather than relying on a single fixed substitution. This approach significantly reduced the effectiveness of frequency analysis, which had compromised simpler monoalphabetic ciphers such as the Simple Substitution Cipher.
Affine Cipher
The Affine Cipher is a type of monoalphabetic substitution cipher that combines multiplication and addition operations to transform plaintext letters into ciphertext. Each letter x in the plaintext is first converted to a numeric value, typically A=0 through Z=25, and then encrypted using the function E(x) = (ax + b) mod 26, where a and b are keys chosen such that a is coprime with 26.
A1Z26 Cipher
The A1Z26 Cipher is a straightforward substitution cipher in which each letter of the alphabet is replaced by its corresponding numerical position. Specifically, A=1, B=2, C=3, continuing through Z=26. This simple mapping transforms plaintext into a sequence of numbers, creating a numeric representation of the original message while maintaining a direct, one-to-one correspondence between letters and values.