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secp256k1
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Minor comment improvements.

This commit is contained in:
Gregory Maxwell 2015-10-19 23:28:41 +00:00
parent 131afe5bf5
commit 6c476a8a9b
2 changed files with 5 additions and 4 deletions
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5
src/ecdsa_impl.h
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@ -238,11 +238,11 @@ static int secp256k1_ecdsa_sig_verify(const secp256k1_ecmult_context *ctx, const
* secp256k1_gej_eq_x implements the (xr * pr.z^2 mod p == pr.x) test.
*/
if (secp256k1_gej_eq_x_var(&xr, &pr)) {
/* xr.x == xr * xr.z^2 mod p, so the signature is valid. */
/* xr * pr.z^2 mod p == pr.x, so the signature is valid. */
return 1;
}
if (secp256k1_fe_cmp_var(&xr, &secp256k1_ecdsa_const_p_minus_order) >= 0) {
/* xr + p >= n, so we can skip testing the second case. */
/* xr + n >= p, so we can skip testing the second case. */
return 0;
}
secp256k1_fe_add(&xr, &secp256k1_ecdsa_const_order_as_fe);
@ -301,6 +301,7 @@ static int secp256k1_ecdsa_sig_sign(const secp256k1_ecmult_gen_context *ctx, sec
secp256k1_scalar_set_b32(sigr, b, &overflow);
if (secp256k1_scalar_is_zero(sigr)) {
/* P.x = order is on the curve, so technically sig->r could end up zero, which would be an invalid signature. */
/* This branch is cryptographically unreachable as hitting it requires finding the discrete log of P.x = N. */
secp256k1_gej_clear(&rp);
secp256k1_ge_clear(&r);
return 0;

4
src/ecmult_gen_impl.h
View File

@ -182,7 +182,7 @@ static void secp256k1_ecmult_gen_blind(secp256k1_ecmult_gen_context *ctx, const
secp256k1_rfc6979_hmac_sha256_generate(&rng, nonce32, 32);
retry = !secp256k1_fe_set_b32(&s, nonce32);
retry |= secp256k1_fe_is_zero(&s);
} while (retry);
} while (retry); /* This branch true is cryptographically unreachable. Requires sha256_hmac output > Fp. */
/* Randomize the projection to defend against multiplier sidechannels. */
secp256k1_gej_rescale(&ctx->initial, &s);
secp256k1_fe_clear(&s);
@ -191,7 +191,7 @@ static void secp256k1_ecmult_gen_blind(secp256k1_ecmult_gen_context *ctx, const
secp256k1_scalar_set_b32(&b, nonce32, &retry);
/* A blinding value of 0 works, but would undermine the projection hardening. */
retry |= secp256k1_scalar_is_zero(&b);
} while (retry);
} while (retry); /* This branch true is cryptographically unreachable. Requires sha256_hmac output > order. */
secp256k1_rfc6979_hmac_sha256_finalize(&rng);
memset(nonce32, 0, 32);
secp256k1_ecmult_gen(ctx, &gb, &b);