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Add curve25519 computation.

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This commit is contained in:
NIIBE Yutaka
2014-04-15 10:28:17 +09:00
parent 4d6f59079a
commit 85b2698bb3
5 changed files with 276 additions and 97 deletions
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82
src/ecc-edwards.c
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@@ -93,10 +93,6 @@
* Gy: 0x6666666666666666666666666666666666666666666666666666666666666658
*/
static const bn256 p25519[1] = {
{{ 0xffffffed, 0xffffffff, 0xffffffff, 0xffffffff,
0xffffffff, 0xffffffff, 0xffffffff, 0x7fffffff }} };
/* d + 2^255 - 19 */
static const bn256 coefficient_d[1] = {
{{ 0x135978a3, 0x75eb4dca, 0x4141d8ab, 0x00700a4d,
@@ -240,84 +236,6 @@ point_add (ptc *X, const ptc *A, const ac *B)
}
static void
add19 (bn256 *r, bn256 *x)
{
uint32_t v;
int i;
v = 19;
for (i = 0; i < BN256_WORDS; i++)
{
r->word[i] = x->word[i] + v;
v = (r->word[i] < v);
}
}
/*
* @brief X = A mod 2^255-19
*
* It's precisely modulo 2^255-19 (unlike mod25638_reduce).
*/
static void
mod25519_reduce (bn256 *X)
{
uint32_t q;
bn256 r0[1], r1[1];
int flag;
memcpy (r0, X, sizeof (bn256));
q = (r0->word[7] >> 31);
r0->word[7] &= 0x7fffffff;
if (q)
{
add19 (r0, r0);
q = (r0->word[7] >> 31);
r0->word[7] &= 0x7fffffff;
if (q)
{
add19 (r1, r0);
q = (r1->word[7] >> 31);
r1->word[7] &= 0x7fffffff;
flag = 0;
}
else
flag = 1;
}
else
{
add19 (r1, r0); /* dummy */
q = (r1->word[7] >> 31); /* dummy */
r1->word[7] &= 0x7fffffff; /* dummy */
if (q)
flag = 2;
else
flag = 3;
}
if (flag)
{
add19 (r1, r0);
q = (r1->word[7] >> 31);
r1->word[7] &= 0x7fffffff;
if (q)
memcpy (X, r1, sizeof (bn256));
else
memcpy (X, r0, sizeof (bn256));
}
else
{
if (q)
{
asm volatile ("" : : "r" (q) : "memory");
memcpy (X, r1, sizeof (bn256));
asm volatile ("" : : "r" (q) : "memory");
}
else
memcpy (X, r1, sizeof (bn256));
}
}
/**
* @brief X = convert A
*