The Mexican Army Cipher Wheel is a polyalphabetic monographic substitution cipher.
The wheel consists of five discs, the position of which can be freely adjusted.
From the outside to the inside:
- Letters A – Z
- numbers 01 – 26
- numbers 27 – 52
- Numbers 53 – 78
- Numbers 79 – 100
The key is defined by
- four numbers that lie below the A
- four letters for the numbers 01, 27, 53 and 79.
Then the letters are encrypted by the respective numbers or the four numbers are decrypted to the letters.