The In MixColumns transformation of AES consists of a matrix–vector multiplication in the field GF(2^8) with irreducible polynomial P(x) = x^8+x^4+x^3+x+1 as well during the decryption of AES. Let b = (b7x7+. . .+b0) be one of the (four) input bytes to the vector– matrix multiplication. Each input byte is multiplied with the constants 0E, 0B, 0D and 09. Your task is to provide exact equations for computing those three constant multiplications after reductions. We denote the result by d = (d7x7+. . .+d0).