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authorMatthias Schiffer <mschiffer@universe-factory.net>2012-03-14 10:47:16 +0100
committerMatthias Schiffer <mschiffer@universe-factory.net>2012-03-14 10:47:16 +0100
commiteec9db5e4d9cd5dff638819566024fad8c56a8a1 (patch)
treedbca98eee9e224476645c18e7d99a7bfe1bf9eb5 /src/ec25519.c
parenta3345c7d5b0dd7812f08d2eb8859eedd5623a59e (diff)
downloadlibuecc-eec9db5e4d9cd5dff638819566024fad8c56a8a1.tar
libuecc-eec9db5e4d9cd5dff638819566024fad8c56a8a1.zip
Some more renamed, some utility functions
Diffstat (limited to 'src/ec25519.c')
-rw-r--r--src/ec25519.c38
1 files changed, 21 insertions, 17 deletions
diff --git a/src/ec25519.c b/src/ec25519.c
index 889264d..b9ca4e9 100644
--- a/src/ec25519.c
+++ b/src/ec25519.c
@@ -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) {