Thales Dis France Sas

Olivier Adjonyo Koffi Benit

David Vigilant

Mylène Roussellet

Provided is a method for securing against high-order side-channel attacks wherein a substep of field inversion is performed by a cryptographic device. The method includes computing (S) a Dirac output value, adding (S) 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 (S) from said (n+1) additive sharing to a (n+1)-multiplicative sharing, performing an inversion of each share of the (n+1)-multiplicative sharing (S), performing a conversion of the inverted shares (S) from said multiplicative sharing to a (n+1)-additive sharing to obtain a third set of shares, and adding (S) said Dirac output value to one of said shares of the third set of shares. Other embodiments disclosed.

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Rosny-sous-bois, France

Olivier Adjonyo Koffi Benit