Patent ID: 8817974

Claim:
A method for integrity protected calculation of a cryptographic function on a cryptographic processor comprising: performing on a cryptographic processor an operation c=a∘b in a cryptographic function f p,q (x 1 , x 2 , . . . , x n ) defined over a commutative ring R, wherein a and b are any one of x 1 , x 2 , . . . , x n and p and q are prime such that p p≡1 (MOD q) and q q≡1 (MOD p); choosing a′ and b′ corresponding to a and b such that a′ and b′ are elements of a commutative ring R′, with a modulus m that is coprime with p·q, wherein a′ and b′ are a cyclic redundancy check of a and b; computing c′=a′∘b′; computing a″=CRT p,q (a, a′) and b″=CRT p,q (b, b′), where CRT is a Chinese Remainder Theorem defined as CRT p,q (a,b)=(a p p+b q q) MOD pq; computing c″=a″∘″b″; calculating a mapping of c″ into R′=c″ mod m; and determining if the mapping of c″ into R′ equals c′, and then indicating that no fault is detected, wherein if the mapping of c″ into R′ equals c′ then repeating the above steps to further calculate the cryptographic function f p,q (x 1 , x 2 , . . . , x n ) for other values of a and b, otherwise indicate that the calculation of the cryptographic function f p,q (x 1 , x 2 , . . . , x n ) is invalid.