the used substitution box is inverted with respect to table sbox and is generally noted sbox u2212 1 then the byte provided by box 105 is multiplied by a line matrix of value a b c d symbolized by four multipliers 115 to 118 to obtain a weighted expansion of the byte originating from box 105 into a 32 bit word the obtained word is placed in a register 108 reg 3 respecting the order of the multiplication coefficient line matrix as will be seen hereafter such multiplications enable executing a first step of the columns mixing mixcolumn of the aes algorithm to perform the polynomial multiplication most often each column of the matrix resulting from the substitution box is multiplied by a square matrix having as values bytes in hexadecimal notation and for the ciphering a 02 d 03 b 01 and c 01 for the first line b a d and c for the second line c b a and d for the third line and d c b and a for the fourth line for the deciphering the hexadecimal values are a 0e b 09 c 0d and d 0b the word originating from register 108 is submitted to a rotation block 109 rotate which performs a circular permutation of the bytes of the input word and corresponds to a second step of the column mixing mixcolumns and of columns shifting shiftrows of the aes algorithm the rotation performed by block 109 depends on the byte selected.