Finding matrices with very specific properties

[RossH]

Hello. I am writing an encryption algorithm for a program and have decided to use a hill cipher. My problem is that for the hill cipher, I have to have matrices with very specific properties. How might I go about finding 3 matrices of size 4x4 such that all of the matrices are integer-only and have integer inverses. Do you have any idea?

 

[Bill Simpson]

http://en.wikipedia.org/wiki/Integer_matrix