y matrix.Now, separate the image pixel values into blocks of size four,each block will be converted to a vector of size 4 1(P1; P2; P3; ...), then multiply the self-invertible key matrix Km byeach vector and take modulo 256 to get the ciphered vectors(C1; C2; C3; ...). After that, reconstruct the ciphered image C fromthe values in the ciphered vectors and send it to the other party.The following calculations are repeated for each block: