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| author | Matthias Schiffer <mschiffer@universe-factory.net> | 2012-03-16 20:59:33 +0100 |
|---|---|---|
| committer | Matthias Schiffer <mschiffer@universe-factory.net> | 2012-03-16 20:59:33 +0100 |
| commit | 3ea1ba496ece8d6e0e90b4b6f32b59ae62052cda (patch) | |
| tree | 58c738732657baceccbdbd8b56b7d55ce84907fe | |
| parent | a3743a365adc74d79cac500980f216d5ece3f187 (diff) | |
| download | libuecc-3ea1ba496ece8d6e0e90b4b6f32b59ae62052cda.tar libuecc-3ea1ba496ece8d6e0e90b4b6f32b59ae62052cda.zip | |
For Edwards curves, the identity element isn't at infinity, so rename the identity check function accordingly
| -rw-r--r-- | include/libuecc/ecc.h | 2 | ||||
| -rw-r--r-- | src/ec25519.c | 13 |
2 files changed, 8 insertions, 7 deletions
diff --git a/include/libuecc/ecc.h b/include/libuecc/ecc.h index f535702..a422ecb 100644 --- a/include/libuecc/ecc.h +++ b/include/libuecc/ecc.h @@ -45,7 +45,7 @@ typedef struct _ecc_25519_work { void ecc_25519_load(ecc_25519_work *out, const ecc_public_key_256 *in); void ecc_25519_store(ecc_public_key_256 *out, const ecc_25519_work *in); -int ecc_25519_is_infinity(const ecc_25519_work *in); +int ecc_25519_is_identity(const ecc_25519_work *in); void ecc_25519_add(ecc_25519_work *out, const ecc_25519_work *in1, const ecc_25519_work *in2); void ecc_25519_double(ecc_25519_work *out, const ecc_25519_work *in); void ecc_25519_scalarmult(ecc_25519_work *out, const ecc_secret_key_256 *n, const ecc_25519_work *base); diff --git a/src/ec25519.c b/src/ec25519.c index b9ca4e9..dfb806b 100644 --- a/src/ec25519.c +++ b/src/ec25519.c @@ -387,10 +387,10 @@ void ecc_25519_store(ecc_public_key_256 *out, const ecc_25519_work *in) { out->p[31] |= (y[0] << 7); } -static const ecc_25519_work infty = {{0}, {0}, {1}}; +static const ecc_25519_work id = {{1}, {0}, {0}}; -int ecc_25519_is_infinity(const ecc_25519_work *in) { - return (check_zero(in->X)|check_zero(in->Y)); +int ecc_25519_is_identity(const ecc_25519_work *in) { + return (check_zero(in->X)|check_zero(in->Y)|check_zero(in->Z)); } void ecc_25519_double(ecc_25519_work *out, const ecc_25519_work *in) { @@ -411,11 +411,12 @@ 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, out, &infty, ecc_25519_is_infinity(out)); + selectw(out, out, &id, ecc_25519_is_identity(out)); } void ecc_25519_add(ecc_25519_work *out, const ecc_25519_work *in1, const ecc_25519_work *in2) { unsigned int A[32], B[32], C[32], D[32], E[32], H[32], I[32], t0[32], t1[32], t2[32], t3[32], t4[32], t5[32], t6[32], t7[32], t8[32]; + int id1 = ecc_25519_is_identity(in1), id2 = ecc_25519_is_identity(in2); mult(A, in1->Z, in2->Z); square(t0, A); @@ -436,8 +437,8 @@ 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, out, in1, check_zero(t3)); - selectw(out, out, in2, check_zero(t2)); + selectw(out, out, in1, id2); + selectw(out, out, in2, id1); } void ecc_25519_scalarmult(ecc_25519_work *out, const ecc_secret_key_256 *n, const ecc_25519_work *base) { |