coelner/gnuk
1
0
Fork 0
mirror of https://salsa.debian.org/gnuk-team/gnuk/gnuk.git synced 2024-09-21 03:10:08 +00:00
Code Issues Packages Projects Releases Wiki Activity

fast reduction for modp256_shift

Browse Source
This commit is contained in:
NIIBE Yutaka 2011-10-11 22:46:39 +09:00
parent 434cf67470
commit 23c411188c
1 changed files with 11 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
src/modp256.c
View File

@ -274,19 +274,23 @@ modp256_inv (bn256 *C, const bn256 *a)
void void
modp256_shift (bn256 *X, const bn256 *A, int shift) modp256_shift (bn256 *X, const bn256 *A, int shift)
{ {
int carry; uint32_t carry;
bn256 tmp[1];
carry = bn256_shift (X, A, shift); carry = bn256_shift (X, A, shift);
if (shift < 0) if (shift < 0)
return; return;
while (carry) memset (tmp, 0, sizeof (bn256));
{ tmp->words[7] = carry;
int borrow; tmp->words[0] = carry;
modp256_add (X, X, tmp);
borrow = bn256_sub (X, X, P256); tmp->words[7] = 0;
carry -= borrow; tmp->words[0] = 0;
} tmp->words[6] = carry;
tmp->words[3] = carry;
modp256_sub (X, X, tmp);
if (bn256_is_ge (X, P256)) if (bn256_is_ge (X, P256))
bn256_sub (X, X, P256); bn256_sub (X, X, P256);