Thales Dis France Sas

Inside Secure

Mylène Rousselet

David Vigilant

Christophe Clavier

Georges Gagnerot

Vincent Verneuil

Benoît Feix

Fabrice Perion

Provided is a method to secure against side channel attacks performing a cryptographic operation of a cryptographic algorithm. It includes selecting a multiplier integer t and determining a second integer q' by multiplying said first integer q, determining (S) an invertible random polynomial R[X] in said first polynomial ring R, randomizing (S) the coefficients Ai of said input polynomial A[X] based on said determined second integer q′ and said determined random polynomial R[X], performing (S) the polynomial operation of the cryptographic operation on said randomized input polynomials A″[X], and unmasking (S) the result polynomial Res″(X) by applying to its coefficients a modulo said first integer q operation. Other embodiments disclosed.

Method secured against side-channel attacks performing a cryptographic algorithm comprising a polynomial operation

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SAINT SAVOURNIN, France

Mylène Rousselet