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fast-final-expo

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This commit is contained in:
Soraba Shrine de Gorachya
2018-12-19 00:17:30 -08:00
parent 62d385ab71
commit 907d5e92d0
1 changed files with 102 additions and 1 deletions
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103
crypto/sm9/sm9_rate.c Normal file → Executable file
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@@ -2367,6 +2367,7 @@ static int frobenius_twice(point_t *R, const point_t *P, const BIGNUM *p, BN_CTX
return 1;
}
static int final_expo(fp12_t r, const fp12_t a, const BIGNUM *k, const BIGNUM *p, BN_CTX *ctx)
{
int i, n;
@@ -2393,6 +2394,103 @@ static int final_expo(fp12_t r, const fp12_t a, const BIGNUM *k, const BIGNUM *p
return 1;
}
static int fast_final_expo(fp12_t r, const fp12_t a, const BIGNUM *k, const BIGNUM *p, BN_CTX *ctx)
{
// (p^4-p^2+1)/n will be directly used to finish the 3rd step with k unused here.
int i, n;
fp12_t t;
fp12_t t0;
fp12_init(t, ctx);
fp12_init(t0, ctx);
if (!fp12_copy(t, a)) {
return 0;
}
if (!fp12_copy(t0, a)) {
return 0;
}
// first step: a1 = a ^ (p^6-1)
if (!fp12_inv(t0, t, p, ctx)) { // t0 = a ^ (-1)
return 0;
}
if (!BN_sub(t[0][1][0], p, t[0][1][0])
|| !BN_sub(t[0][1][1], p, t[0][1][1])
|| !BN_sub(t[1][0][0], p, t[1][0][0])
|| !BN_sub(t[1][0][1], p, t[1][0][1])
|| !BN_sub(t[2][1][0], p, t[2][1][0])
|| !BN_sub(t[2][1][1], p, t[2][1][1])) { // t = a ^ (p^6)
return 0;
}
if (!fp12_mul(t, t0, t, p, ctx)) { // t = t0 * t = a ^ (p^6-1) = a1
return 0;
}
// second step: a = a ^ (p^2+1)
if (!fp12_copy(t0, t)) { // t0 = t = a1
return 0;
}
const char *power_p2[] = {
"5958342662901643427453578939755302545063035311436308304692",
"82434016654578246438872420442344325702149582327179867092849556861979152020041",
"5958342662901643427453578939755302545063035311436308304691",
"82434016654578246438872420442344325702149582327179867092849556861979152020042"};
BIGNUM *par[4];
for(int i=0;i<4;++i) {
par[i] = BN_new();
BN_init(par[i]);
if(!BN_dec2bn(&par[i], power_p2[i])){
return 0;
}
}
if (!BN_sub(t[0][1][0], p, t[0][1][0])
|| !BN_sub(t[0][1][1], p, t[0][1][1])
|| !BN_mod_mul(t[1][0][0], t[1][0][0], par[0], p, ctx)
|| !BN_mod_mul(t[1][0][1], t[1][0][1], par[0], p, ctx)
|| !BN_mod_mul(t[1][1][0], t[1][1][0], par[1], p, ctx)
|| !BN_mod_mul(t[1][1][1], t[1][1][1], par[1], p, ctx)
|| !BN_mod_mul(t[2][0][0], t[2][0][0], par[2], p, ctx)
|| !BN_mod_mul(t[2][0][1], t[2][0][1], par[2], p, ctx)
|| !BN_mod_mul(t[2][1][0], t[2][1][0], par[3], p, ctx)
|| !BN_mod_mul(t[2][1][1], t[2][1][1], par[3], p, ctx)) { // t = a1 ^ (p^2)
return 0;
}
if (!fp12_mul(t, t0, t, p, ctx)) { // t = t0 * t = a ^ (p^2+1) = a2
return 0;
}
// third step: a = a ^ [(p^4-p^2+1)/n]
BIGNUM *x = BN_new();
BN_init(x);
// this is (p^4-p^2+1)/n
const char *power_p3 = "56016940484435473570363458812714626596371"
"56263396225483794771796879929232299116963"
"85989797265808925975765890463898744492959"
"90589989684454491684765426953541105430217"
"12895268418170653274635803649243300415902"
"97941432449745271567755349";
if (!BN_dec2bn(&x, power_p3)){
return 0;
}
n = BN_num_bits(x);
for (i = n - 2; i >= 0; i--) {
if (!fp12_sqr(t, t, p, ctx)) {
return 0;
}
if (BN_is_bit_set(x, i)) {
if (!fp12_mul(t, t, a, p, ctx)) {
return 0;
}
}
}
fp12_copy(r, t);
return 1;
}
static int rate(fp12_t f, const point_t *Q, const BIGNUM *xP, const BIGNUM *yP,
const BIGNUM *a, const BIGNUM *k, const BIGNUM *p, BN_CTX *ctx)
{
@@ -2473,8 +2571,11 @@ static int rate(fp12_t f, const point_t *Q, const BIGNUM *xP, const BIGNUM *yP,
point_add(&T, &T, &Q2, p, ctx);
/* f = f^((p^12 - 1)/n) */
#ifndef SM9_FAST
final_expo(f, f, k, p, ctx);
#else
fast_final_expo(f, f, k, p, ctx); // (p^6-1) * (p^2+1) * [(p^4-p^2+1)/n]
#endif
point_cleanup(&T);
point_cleanup(&Q1);