frost/secp256k1-zkp
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Add bounds checking to field element setters

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This commit is contained in:
Pieter Wuille
2014-11-24 12:38:05 +01:00
parent bb2cd94e09
commit d907ebc0e3
10 changed files with 37 additions and 24 deletions
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6
src/field_5x52_impl.h
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@@ -150,7 +150,7 @@ SECP256K1_INLINE static int secp256k1_fe_equal(const secp256k1_fe_t *a, const se
return ((t[0]^u[0]) | (t[1]^u[1]) | (t[2]^u[2]) | (t[3]^u[3]) | (t[4]^u[4])) == 0;
}
static void secp256k1_fe_set_b32(secp256k1_fe_t *r, const unsigned char *a) {
static int secp256k1_fe_set_b32(secp256k1_fe_t *r, const unsigned char *a) {
r->n[0] = r->n[1] = r->n[2] = r->n[3] = r->n[4] = 0;
for (int i=0; i<32; i++) {
for (int j=0; j<2; j++) {
@@ -159,11 +159,15 @@ static void secp256k1_fe_set_b32(secp256k1_fe_t *r, const unsigned char *a) {
r->n[limb] |= (uint64_t)((a[31-i] >> (4*j)) & 0xF) << shift;
}
}
if (r->n[4] == 0x0FFFFFFFFFFFFULL && (r->n[3] & r->n[2] & r->n[1]) == 0xFFFFFFFFFFFFFULL && r->n[0] >= 0xFFFFEFFFFFC2FULL) {
return 0;
}
#ifdef VERIFY
r->magnitude = 1;
r->normalized = 1;
secp256k1_fe_verify(r);
#endif
return 1;
}
/** Convert a field element to a 32-byte big endian value. Requires the input to be normalized */