At some point, this is the beginning of a collection of puzzles for kids learning basic math.
Multi-Crypto is a simple puzzle generator to help kids work on their multiplication and subtraction, while feeling like a spy decoding a secret message. A puzzle encodes a phrase, where each letter is represented by a math problem in the form of:
(a x b) - (c x d)
with the result being an index between 1-26, representing a position in the decoder key. The decoder key is deciphered just as the secret message is: with math problems.
Check out this example of a Multi-Crypto puzzle.