Effect of self invertible matrix on cipher tetragraphic trifunction

In this paper, we give some solutions L2×2 for L2×23≡A2×2(modN) when A2×2 is zero, identity, [ ef00 ] and [ ef0h ] matrices. As a result, the use of a secret key L4×4=[ L2×2I−L2×2I+L2×2−L2×2 ] should be avoided in order to enhance the security of Cipher Tetragraphic Trifunction transformations, C4×J(t)≡L4×4P4×j(modN) where t∈ { 1,2,3 }, C4×j(t) is ciphertext and P4×j is plaintext.