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Fixed square_root()

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This commit is contained in:
Matthias Schiffer 2012-03-14 06:35:12 +01:00
parent 0f4ce2313c
commit 50019f858f
1 changed files with 16 additions and 13 deletions
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19
src/ec25519.c
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@ -194,6 +194,8 @@ static const unsigned int rho_s[32] = {
};
static const unsigned int zero[32] = {0};
static void square_root(unsigned int out[32], const unsigned int z[32]) {
static const unsigned int minus1[32] = {
0xec, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
@ -201,8 +203,7 @@ static const unsigned int minus1[32] = {
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f
};
static void square_root(unsigned int out[32], const unsigned int z[32]) {
/* raise z to the (2^252-2)th power */
/* raise z to power (2^252-2), check if power (2^253-5) equals -1 */
unsigned int z2[32];
unsigned int z9[32];
@ -214,7 +215,8 @@ static void square_root(unsigned int out[32], const unsigned int z[32]) {
unsigned int z2_100_0[32];
unsigned int t0[32];
unsigned int t1[32];
unsigned int rt_sq[32];
unsigned int z2_252_1[32];
unsigned int z2_252_1_rho_s[32];
int i;
/* 2 */ square(z2, z);
@ -264,14 +266,15 @@ static void square_root(unsigned int out[32], const unsigned int z[32]) {
/* 2^251 - 2^1 */ square(t1, t0);
/* 2^252 - 2^2 */ square(t0, t1);
/* 2^252 - 2^1 */ mult(z2_252_1, t0, z2);
/* 2^252 - 2 */ mult(t1, t0, z2);
/* 2^253 - 2^3 */ square(t1, t0);
/* 2^253 - 6 */ mult(t0, t1, z2);
/* 2^253 - 5 */ mult(t1, t0, z);
mult(t0, t1, rho_s);
mult(z2_252_1_rho_s, z2_252_1, rho_s);
square(rt_sq, t1);
select(out, t0, t1, check_equal(rt_sq, minus1));
select(out, z2_252_1_rho_s, z2_252_1, check_equal(t1, minus1));
}
static void recip(unsigned int out[32], const unsigned int z[32]) {