Yep, this system is one of the type, known as "The One Time Pad" Encryption System. Very easy, to learn, and use, and very hard to crack, from just looking at the Coded Message. The same Matrix PAD, must be used on both ends of the Comms Link, and the Security of the System, ONLY depends on the Physical Security of the PADs, themselves. These are the MOST SECURE, of all Encryption Systems available to a Regular Joe. They can be Brute Forced, with a Massive computer, but it takes a very LONG, Long Time, and usually not worth the effort, if the PADs are changed routinely, as the message is usually not "Timely" by the time the PAD is cracked. ...... YMMV....
Interesting way of producing cyphers for secure communications. It's particularly useful for non digital communications where computer encryption is impractical.