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slide() -> slide_vartime() and move comments to the right place

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This commit is contained in:
Frank Denis
2017-10-19 22:11:43 +02:00
parent 9f3a2e775b
commit a944db7a76
1 changed files with 17 additions and 14 deletions
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src/libsodium/crypto_core/curve25519/ref10/curve25519_ref10.c
+17 -14
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@@ -1354,7 +1354,7 @@ ge_add(ge_p1p1 *r, const ge_p3 *p, const ge_cached *q)
}
static void
slide(signed char *r, const unsigned char *a)
slide_vartime(signed char *r, const unsigned char *a)
{
int i;
int b;
@@ -1718,20 +1718,13 @@ ge_tobytes(unsigned char *s, const ge_p2 *h)
s[31] ^= fe_isnegative(x) << 7;
}
/*
h = a * B
where a = a[0]+256*a[1]+...+256^31 a[31]
B is the Ed25519 base point (x,4/5) with x positive.
*
Preconditions:
a[31] <= 127
*/
/*
r = a * A + b * B
where a = a[0]+256*a[1]+...+256^31 a[31].
and b = b[0]+256*b[1]+...+256^31 b[31].
B is the Ed25519 base point (x,4/5) with x positive.
Only used for signatures verification.
*/
void
@@ -1746,8 +1739,8 @@ ge_double_scalarmult_vartime(ge_p2 *r, const unsigned char *a, const ge_p3 *A,
ge_p3 A2;
int i;
slide(aslide, a);
slide(bslide, b);
slide_vartime(aslide, a);
slide_vartime(bslide, b);
ge_p3_to_cached(&Ai[0], A);
ge_p3_dbl(&t, A);
@@ -1777,8 +1770,9 @@ ge_double_scalarmult_vartime(ge_p2 *r, const unsigned char *a, const ge_p3 *A,
ge_p2_0(r);
for (i = 255; i >= 0; --i) {
if (aslide[i] || bslide[i])
if (aslide[i] || bslide[i]) {
break;
}
}
for (; i >= 0; --i) {
@@ -1818,7 +1812,7 @@ ge_scalarmult_vartime(ge_p3 *r, const unsigned char *a, const ge_p3 *A)
ge_p3 A2;
int i;
slide(aslide, a);
slide_vartime(aslide, a);
ge_p3_to_cached(&Ai[0], A);
ge_p3_dbl(&t, A);
@@ -1869,6 +1863,15 @@ ge_scalarmult_vartime(ge_p3 *r, const unsigned char *a, const ge_p3 *A)
#endif
/*
h = a * B (with precomputation)
where a = a[0]+256*a[1]+...+256^31 a[31]
B is the Ed25519 base point (x,4/5) with x positive.
*
Preconditions:
a[31] <= 127
*/
void
ge_scalarmult_base(ge_p3 *h, const unsigned char *a)
{