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Merge pull request #134

29ae131 Make scalar_add_bit test's overflow detection exact (Pieter Wuille)
master
Pieter Wuille 8 years ago
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commit
4d879a3a66
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  1. 4
      src/scalar.h
  2. 7
      src/scalar_4x64_impl.h
  3. 7
      src/scalar_8x32_impl.h
  4. 3
      src/tests.c

4
src/scalar.h

@ -42,8 +42,8 @@ static void secp256k1_scalar_set_int(secp256k1_scalar_t *r, unsigned int v); @@ -42,8 +42,8 @@ static void secp256k1_scalar_set_int(secp256k1_scalar_t *r, unsigned int v);
/** Convert a scalar to a byte array. */
static void secp256k1_scalar_get_b32(unsigned char *bin, const secp256k1_scalar_t* a);
/** Add two scalars together (modulo the group order). */
static void secp256k1_scalar_add(secp256k1_scalar_t *r, const secp256k1_scalar_t *a, const secp256k1_scalar_t *b);
/** Add two scalars together (modulo the group order). Returns whether it overflowed. */
static int secp256k1_scalar_add(secp256k1_scalar_t *r, const secp256k1_scalar_t *a, const secp256k1_scalar_t *b);
/** Add a power of two to a scalar. The result is not allowed to overflow. */
static void secp256k1_scalar_add_bit(secp256k1_scalar_t *r, unsigned int bit);

7
src/scalar_4x64_impl.h

@ -81,7 +81,7 @@ SECP256K1_INLINE static int secp256k1_scalar_reduce(secp256k1_scalar_t *r, unsig @@ -81,7 +81,7 @@ SECP256K1_INLINE static int secp256k1_scalar_reduce(secp256k1_scalar_t *r, unsig
return overflow;
}
static void secp256k1_scalar_add(secp256k1_scalar_t *r, const secp256k1_scalar_t *a, const secp256k1_scalar_t *b) {
static int secp256k1_scalar_add(secp256k1_scalar_t *r, const secp256k1_scalar_t *a, const secp256k1_scalar_t *b) {
uint128_t t = (uint128_t)a->d[0] + b->d[0];
r->d[0] = t & 0xFFFFFFFFFFFFFFFFULL; t >>= 64;
t += (uint128_t)a->d[1] + b->d[1];
@ -90,7 +90,10 @@ static void secp256k1_scalar_add(secp256k1_scalar_t *r, const secp256k1_scalar_t @@ -90,7 +90,10 @@ static void secp256k1_scalar_add(secp256k1_scalar_t *r, const secp256k1_scalar_t
r->d[2] = t & 0xFFFFFFFFFFFFFFFFULL; t >>= 64;
t += (uint128_t)a->d[3] + b->d[3];
r->d[3] = t & 0xFFFFFFFFFFFFFFFFULL; t >>= 64;
secp256k1_scalar_reduce(r, t + secp256k1_scalar_check_overflow(r));
int overflow = t + secp256k1_scalar_check_overflow(r);
VERIFY_CHECK(overflow == 0 || overflow == 1);
secp256k1_scalar_reduce(r, overflow);
return overflow;
}
static void secp256k1_scalar_add_bit(secp256k1_scalar_t *r, unsigned int bit) {

7
src/scalar_8x32_impl.h

@ -111,7 +111,7 @@ SECP256K1_INLINE static int secp256k1_scalar_reduce(secp256k1_scalar_t *r, uint3 @@ -111,7 +111,7 @@ SECP256K1_INLINE static int secp256k1_scalar_reduce(secp256k1_scalar_t *r, uint3
return overflow;
}
static void secp256k1_scalar_add(secp256k1_scalar_t *r, const secp256k1_scalar_t *a, const secp256k1_scalar_t *b) {
static int secp256k1_scalar_add(secp256k1_scalar_t *r, const secp256k1_scalar_t *a, const secp256k1_scalar_t *b) {
uint64_t t = (uint64_t)a->d[0] + b->d[0];
r->d[0] = t & 0xFFFFFFFFULL; t >>= 32;
t += (uint64_t)a->d[1] + b->d[1];
@ -128,7 +128,10 @@ static void secp256k1_scalar_add(secp256k1_scalar_t *r, const secp256k1_scalar_t @@ -128,7 +128,10 @@ static void secp256k1_scalar_add(secp256k1_scalar_t *r, const secp256k1_scalar_t
r->d[6] = t & 0xFFFFFFFFULL; t >>= 32;
t += (uint64_t)a->d[7] + b->d[7];
r->d[7] = t & 0xFFFFFFFFULL; t >>= 32;
secp256k1_scalar_reduce(r, t + secp256k1_scalar_check_overflow(r));
int overflow = t + secp256k1_scalar_check_overflow(r);
VERIFY_CHECK(overflow == 0 || overflow == 1);
secp256k1_scalar_reduce(r, overflow);
return overflow;
}
static void secp256k1_scalar_add_bit(secp256k1_scalar_t *r, unsigned int bit) {

3
src/tests.c

@ -346,8 +346,7 @@ void scalar_test(void) { @@ -346,8 +346,7 @@ void scalar_test(void) {
secp256k1_scalar_add(&b, &b, &b);
}
secp256k1_scalar_t r1 = s1, r2 = s1;
secp256k1_scalar_add(&r1, &r1, &b);
if (!(secp256k1_scalar_get_bits(&s1, 255, 1) == 1 && secp256k1_scalar_get_bits(&r1, 255, 1) == 0)) {
if (!secp256k1_scalar_add(&r1, &r1, &b)) {
/* No overflow happened. */
secp256k1_scalar_add_bit(&r2, bit);
CHECK(secp256k1_scalar_eq(&r1, &r2));

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