Encryption disk
One of the first devices for encryption was the encryption disk . These are two round metal discs that sit on a common axis and are connected so that the smaller one can rotate on the larger one. Discs of this type have been around since the 15th century. The development of the first cipher disk is attributed to Leon Battista Alberti .
Different alphabets or symbols are indicated on the outer edge of the discs . By turning the disks against each other, these alphabets shift, which is used for encryption. If, for example, the inner B is below the outer A (different from the picture), then this corresponds to a shift cipher by one place, and you can put the ciphertext letter (or, as shown here in the picture, the secret symbol, above the inner plain text letter) for example "8818"). The outer disk contains the ciphertext alphabet and the inner one the plaintext alphabet.
After setting the disks once, it is very easy to achieve monoalphabetic encryption or, if the position of the disks to one another is changed during encryption, even polyalphabetic encryption .
literature
- Simon Singh : Secret Messages . The art of encryption from ancient times to the days of the Internet . Hanser, Munich 2000, ISBN 3-446-19873-3 .
