Madryga

Madryga is a 24-bit block cipher with a variable key length. It operates using just XOR and rotations on whole bytes only, making it suitable for software applications.

When it was published by W E Madryga in 1984 it was intended to offer several significant advantages compared to DES, including variable key length, avoidance of weak keys and efficient implementation in software.

Unfortunately the Madyga cipher has a small data block and does not exhibit the avalanche effect. This creates a weakness for discovery of the parity of the ciphertext for any plaintext. A ciphertext-only attack is also possible.