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Verify the result of GMP modular inverse using non-GMP code

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This commit is contained in:
Pieter Wuille
2015-07-09 11:21:37 -04:00
parent 0cbc8600f3
commit 36b305a82b
2 changed files with 13 additions and 1 deletions
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6
src/scalar_impl.h
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@@ -240,12 +240,16 @@ static void secp256k1_scalar_inverse_var(secp256k1_scalar_t *r, const secp256k1_
#elif defined(USE_SCALAR_INV_NUM)
unsigned char b[32];
secp256k1_num_t n, m;
secp256k1_scalar_get_b32(b, x);
secp256k1_scalar_t t = *x;
secp256k1_scalar_get_b32(b, &t);
secp256k1_num_set_bin(&n, b, 32);
secp256k1_scalar_order_get_num(&m);
secp256k1_num_mod_inverse(&n, &n, &m);
secp256k1_num_get_bin(b, 32, &n);
secp256k1_scalar_set_b32(r, b, NULL);
/* Verify that the inverse was computed correctly, without GMP code. */
secp256k1_scalar_mul(&t, &t, r);
CHECK(secp256k1_scalar_is_one(&t));
#else
#error "Please select scalar inverse implementation"
#endif