Alberti Wheel (1472):

• Proposed by Leon Battista Alberti, an Italian cryptologist.
• Alberti is considered the father of Western Cryptology.
• One of the earliest polyalphabetic substitution ciphers.

Original Cipher Disk:

The original cipher disk consists of two wheels: an outer wheel and an inner wheel.

The outer wheel is fixed, while the inner wheel is flexible allowing for rotations in both directions.

The outer wheel consists of 24 characters: the upper-case letters (except H,J,K,U,W,Y) and the numbers: 1,2,3 and 4.

A B C D E F G I L M N O P Q R S T V X Z 1 2 3 4

The inner wheel also consists of 24 characters.

The characters are arranged as follows:

a c e g k l n p r t v z & x y s o m p i h f d b

To use Alberti Cipher, Alice and Bob would need to agree on a pointer, which is a character from the inner wheel.

• Alberti chose the character k.

We will refer to this original method used by Alberti as: "Alberti Version 0".

Encryption:

1- The sender (Alice) selects a character from the outer wheel, say the letter 'F'. We will call this letter pivot.

2- The sender aligns the outer wheel at the pivot F with the inner wheel at the pointer k.

3- The sender writes the pivot character F in the ciphertext, then begins substitutions, letter by letter