Can someone help me correct this procedure?  I'm so lost as to what I'm supposed to do.  I know I have to take ciphertext, A, B and decrypt it, but I'm not sure where the errors are.  Thanks in advance.

ok, i changed it to using the "uses statement", but I'm not quite sure how the LinearAlgebra[Modular] works still.  And in addition, when I input a encoded msg, A, B into my procedure, it still only gives me exactly what I inputed.  Thanks in advance.