correspond to the size of a matrix element while the size of the random value possibly the pseudo random value used for the linear transformations must correspond to the size of a complete input state by definition an xor type combination is designated as the addition a polynomial multiplication modulo an irreducible polynomial is designated as the multiplication in the left hand portion of fig5 the successive steps of the cyphering algorithm have been shown while in the right hand portion of this drawing the states obtained at the end of each step have been indicated the process starts from an initial state block 31 state init state s 0 corresponds to the code data to be cyphered by the algorithm first step 41 comprises performing an xor type combination of state s 0 with a random value r having the same size as state s 0 for example 128 bits then a conventional step 32 of sub key addition block 32 addroundkey by an xor type combination of first sub key k 0 with the result of the preceding step is executed the obtained state corresponds to state s i r the second phase of the cyphering method comprising executing n u2212 1 turns of a same transformation t is then entered this transformation involves the steps of the conventional process for example aes which are desired to be masked by at least one random value in the example shown these are row shifting.