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Some more renamed, some utility functions

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This commit is contained in:
Matthias Schiffer 2012-03-14 10:47:16 +01:00
parent a3345c7d5b
commit eec9db5e4d
3 changed files with 53 additions and 24 deletions
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38
src/ec25519.c
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@ -135,18 +135,6 @@ static void square(unsigned int out[32], const unsigned int a[32]) {
squeeze(out);
}
static int check_zero(const unsigned int x[32]) {
unsigned int differentbits = 0;
int i;
for (i = 0; i < 32; i++) {
differentbits |= (x[i] & 0xffff);
differentbits |= (x[i] >> 16);
}
return (1-(1 & ((differentbits - 1) >> 16)));
}
static int check_equal(const unsigned int x[32], const unsigned int y[32]) {
unsigned int differentbits = 0;
int i;
@ -156,7 +144,19 @@ static int check_equal(const unsigned int x[32], const unsigned int y[32]) {
differentbits |= ((x[i] ^ y[i]) >> 16);
}
return (1-(1 & ((differentbits - 1) >> 16)));
return (1 & ((differentbits - 1) >> 16));
}
static int check_zero(const unsigned int x[32]) {
static const unsigned int zero[32] = {0};
static const unsigned int p[32] = {
0xed, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f
};
return (check_equal(x, zero) | check_equal(x, p));
}
static void selectw(ecc_25519_work *out, const ecc_25519_work *r, const ecc_25519_work *s, unsigned int b) {
@ -275,7 +275,7 @@ static void square_root(unsigned int out[32], const unsigned int z[32]) {
mult(z2_252_1_rho_s, z2_252_1, rho_s);
select(out, z2_252_1_rho_s, z2_252_1, check_equal(t1, minus1));
select(out, z2_252_1, z2_252_1_rho_s, check_equal(t1, minus1));
}
static void recip(unsigned int out[32], const unsigned int z[32]) {
@ -389,6 +389,10 @@ void ecc_25519_store(ecc_public_key_256 *out, const ecc_25519_work *in) {
static const ecc_25519_work infty = {{0}, {0}, {1}};
int ecc_25519_is_infinity(const ecc_25519_work *in) {
return (check_zero(in->X)|check_zero(in->Y));
}
void ecc_25519_double(ecc_25519_work *out, const ecc_25519_work *in) {
unsigned int A[32], B[32], C[32], D[32], E[32], U[32], t0[32], t1[32], t2[32], t3[32], t4[32], t5[32];
@ -407,7 +411,7 @@ void ecc_25519_double(ecc_25519_work *out, const ecc_25519_work *in) {
sub(t5, C, t4);
mult(out->Y, E, t5);
mult(out->Z, D, E);
selectw(out, &infty, out, check_zero(out->X)*check_zero(out->Y));
selectw(out, out, &infty, ecc_25519_is_infinity(out));
}
void ecc_25519_add(ecc_25519_work *out, const ecc_25519_work *in1, const ecc_25519_work *in2) {
@ -432,8 +436,8 @@ void ecc_25519_add(ecc_25519_work *out, const ecc_25519_work *in1, const ecc_255
mult(out->Y, t7, I);
mult(t8, H, I);
mult(out->Z, A, t8);
selectw(out, in1, out, check_zero(t3));
selectw(out, in2, out, check_zero(t2));
selectw(out, out, in1, check_zero(t3));
selectw(out, out, in2, check_zero(t2));
}
void ecc_25519_scalarmult(ecc_25519_work *out, const ecc_secret_key_256 *n, const ecc_25519_work *base) {