A method for securing against high-order side-channel attacks an execution of a SubBytes step of a block cipher algorithm based on Advanced Encryption Standard and operating on an internal state x split into a first set of (n+1) shares (x0, x1, x2.. xn) by a (n+1)-additive sharing, with n a non-zero integer, said SubBytes step comprising: a substep of affine transformation in GF(2 8) on the state x and a substep of a field inversion in GF *, wherein said substep of field inversion is performed by a cryptographic device and comprises: - computing a Dirac output value by executing at least one Dirac function on a plurality of shares xi of the internal state x, with i an integer in [0,n], said Dirac function being a function defined in GF such that said Dirac output value is equal to 1 when x equals 0 and is equal to 0 otherwise, - adding said Dirac output value to one of said shares of the first set of shares to obtain a second set of shares, - performing a conversion of the second set of shares from said (n+1) additive sharing to a (n+1)-multiplicative sharing, - performing an inversion of each share of the (n+1)-multiplicative sharing, - performing a conversion of the inverted shares from said multiplicative sharing to a (n+1)-additive sharing to obtain a third set of shares, - adding said Dirac output value to one of said shares of the third set of shares, and characterized in that the step of computing the Dirac output value comprises: • replacing one of the shares xi by its binary complementary ~xi with i an integer in {0, 1,.. n} and ~ the Boolean negation operation, and • performing a XOR between (n+1) binary values, each of said binary values being computed by performing a Boolean conjunction AND operation & between a plurality of bits of said shares having different indexes in said shares, wherein XOR is the Boolean exclusive disjunction operation. said SubBytes step comprising: a substep of affine transformation in GF(2 8) on the state x and a substep of a field inversion in GF *, wherein said substep of field inversion is performed by a cryptographic device and comprises: - computing a Dirac output value by executing at least one Dirac function on a plurality of shares xi of the internal state x, with i an integer in [0,n], said Dirac function being a function defined in GF such that said Dirac output value is equal to 1 when x equals 0 and is equal to 0 otherwise, - adding said Dirac output value to one of said shares of the first set of shares to obtain a second set of shares, - performing a conversion of the second set of shares from said (n+1) additive sharing to a (n+1)-multiplicative sharing, - performing an inversion of each share of the (n+1)-multiplicative sharing, - performing a conversion of the inverted shares from said multiplicative sharing to a (n+1)-additive sharing to obtain a third set of shares, - adding said Dirac output value to one of said shares of the third set of shares, - computing a Dirac output value by executing at least one Dirac function on a plurality of shares xi of the internal state x, with i an integer in [0,n], said Dirac function being a function defined in GF such that said Dirac output value is equal to 1 when x equals 0 and is equal to 0 otherwise, - adding said Dirac output value to one of said shares of the first set of shares to obtain a second set of shares, - performing a conversion of the second set of shares from said (n+1) additive sharing to a (n+1)-multiplicative sharing, - performing an inversion of each share of the (n+1)-multiplicative sharing, - performing a conversion of the inverted shares from said multiplicative sharing to a (n+1)-additive sharing to obtain a third set of shares, - adding said Dirac output value to one of said shares of the third set of shares, and characterized in that the step of computing the Dirac output value comprises: • replacing one of the shares xi by its binary complementary ~xi with i an integer in {0, 1,.. n} and ~ the Boolean negation operation, and • performing a XOR between (n+1) binary values, each of said binary values being computed by performing a Boolean conjunction AND operation & between a plurality of bits of said shares having different indexes in said shares, wherein XOR is the Boolean exclusive disjunction operation. • replacing one of the shares xi by its binary complementary ~xi with i an integer in {0, 1,.. n} and ~ the Boolean negation operation, and • performing a XOR between (n+1) binary values, each of said binary values being computed by performing a Boolean conjunction AND operation & between a plurality of bits of said shares having different indexes in said shares, wherein XOR is the Boolean exclusive disjunction operation.