So the plaintext is "hello" (example).
I change it to [8, 5, 11, 11, 15] (offset of each letter in the alphabet)
I multiply the matrix by itself [64, 25, 121, 121, 225]
Then I separate all of the numbers: [6,4,2,5,1,2,1,1,2,1,2,2,5]
And find the offset of the number in the alphabet (F,D,B,E,A,B,A,A,B,A,B,B,E)
It's more of a hash than a cryptography cipher though...
It's very weak. I do find many issues, I'd like to know how I can improve.