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Add ge25519_scalarmult to ed25519-donna

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This reverts commit b1bee409e7.
This commit is contained in:
Saleem Rashid 2017-06-01 15:59:25 +01:00 committed by Pavol Rusnak
parent b472f64c61
commit 6e51be6fe2
1 changed files with 73 additions and 0 deletions
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73
ed25519-donna/ed25519-donna-impl-base.h
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@ -313,6 +313,44 @@ DONNA_INLINE static void ge25519_cmove_stride4(long * r, long * p, long * pos, l
}
#define HAS_CMOVE_STRIDE4
DONNA_INLINE static void ge25519_cmove_stride4b(long * r, long * p, long * pos, long * n, int stride) {
long x0=p[0], x1=p[1], x2=p[2], x3=p[3], y0, y1, y2, y3;
for(p+=stride; p<n; p+=stride) {
int flag=(p==pos);
y0 = p[0];
y1 = p[1];
y2 = p[2];
y3 = p[3];
x0 = flag ? y0 : x0;
x1 = flag ? y1 : x1;
x2 = flag ? y2 : x2;
x3 = flag ? y3 : x3;
}
r[0] = x0;
r[1] = x1;
r[2] = x2;
r[3] = x3;
}
#define HAS_CMOVE_STRIDE4B
static void ge25519_move_conditional_pniels_array(ge25519_pniels * r, const ge25519_pniels * p, int pos, int n) {
#ifdef HAS_CMOVE_STRIDE4B
size_t i;
for(i=0; i<sizeof(ge25519_pniels)/sizeof(long); i+=4) {
ge25519_cmove_stride4b(((long*)r)+i,
((long*)p)+i,
((long*)(p+pos))+i,
((long*)(p+n))+i,
sizeof(ge25519_pniels)/sizeof(long));
}
#else
size_t i;
for(i=0; i<n; i++) {
ge25519_move_conditional_pniels(r, p+i, pos==i);
}
#endif
}
static void ge25519_move_conditional_niels_array(ge25519_niels * r, const uint8_t p[8][96], int pos, int n) {
size_t i;
for(i=0; i<96/sizeof(long); i+=4) {
@ -324,6 +362,41 @@ static void ge25519_move_conditional_niels_array(ge25519_niels * r, const uint8_
}
}
/* computes [s1]p1, constant time */
static void ge25519_scalarmult(ge25519 *r, const ge25519 *p1, const bignum256modm s1) {
signed char slide1[64];
ge25519_pniels pre1[9];
ge25519_pniels pre;
ge25519 d1;
ge25519_p1p1 t;
int32_t i;
contract256_window4_modm(slide1, s1);
/* set neutral */
ge25519_set_neutral(r);
ge25519_full_to_pniels(pre1, r);
ge25519_full_to_pniels(pre1+1, p1);
ge25519_double(&d1, p1);
ge25519_full_to_pniels(pre1+2, &d1);
for (i = 1; i < 7; i++) {
ge25519_pnielsadd(&pre1[i+2], &d1, &pre1[i]);
}
for (i = 63; i >= 0; i--) {
int k=abs(slide1[i]);
ge25519_double_partial(r, r);
ge25519_double_partial(r, r);
ge25519_double_partial(r, r);
ge25519_double_p1p1(&t, r);
ge25519_move_conditional_pniels_array(&pre, pre1, k, 9);
ge25519_p1p1_to_full(r, &t);
ge25519_pnielsadd_p1p1(&t, r, &pre, (unsigned char)slide1[i] >> 7);
ge25519_p1p1_to_partial(r, &t);
}
}
static void
ge25519_scalarmult_base_choose_niels(ge25519_niels *t, const uint8_t table[256][96], uint32_t pos, signed char b) {
bignum25519 neg;