diff options
Diffstat (limited to 'c5/integer.cpp')
| -rw-r--r-- | c5/integer.cpp | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/c5/integer.cpp b/c5/integer.cpp index 0df3540..35312f6 100644 --- a/c5/integer.cpp +++ b/c5/integer.cpp @@ -1295,8 +1295,10 @@ carry2: class PentiumOptimized : public Portable { public: +#ifndef __pic__ // -fpic uses up a register, leaving too few for the asm code static word Add(word *C, const word *A, const word *B, unsigned int N); static word Subtract(word *C, const word *A, const word *B, unsigned int N); +#endif static void Square4(word *R, const word *A); static void Multiply4(word *C, const word *A, const word *B); static void Multiply8(word *C, const word *A, const word *B); @@ -1306,6 +1308,7 @@ typedef PentiumOptimized LowLevel; // Add and Subtract assembly code originally contributed by Alister Lee +#ifndef __pic__ __attribute__((regparm(3))) word PentiumOptimized::Add(word *C, const word *A, const word *B, unsigned int N) { assert (N%2 == 0); @@ -1381,6 +1384,7 @@ __attribute__((regparm(3))) word PentiumOptimized::Subtract(word *C, const word return carry; } +#endif // __pic__ // Comba square and multiply assembly code originally contributed by Leonard Janke @@ -2142,11 +2146,11 @@ void MontgomeryReduce(word *R, word *T, const word *X, const word *M, const word { MultiplyBottom(R, T, X, U, N); MultiplyTop(T, T+N, X, R, M, N); - if (Subtract(R, X+N, T, N)) - { - word carry = Add(R, R, M, N); - assert(carry); - } + word borrow = Subtract(T, X+N, T, N); + // defend against timing attack by doing this Add even when not needed + word carry = Add(T+N, T, M, N); + assert(carry || !borrow); + CopyWords(R, T + (borrow ? N : 0), N); } // R[N] --- result = X/(2**(WORD_BITS*N/2)) mod M |