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Merge feee029d29 into merged_master (Elements PR ElementsProject/elements#1020)

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Messy merge conflicts because this PR backported some ad-hoc stuff from
upstream while keeping a few things that upstream deleted. Hopefully
reviewing is easier than doing this in the first place, since ultimately
all I did was delete code from one side or another of the conflicts.
(Ok, I also changed some boost optional stuff to std::optional, and had
to patch up a test file for test framework changes.)

When reviewing the detailed crypto, bear in mind that taptweaks, like all
hashes are the kind of crypto that cannot be subtly wrong -- it will either
fail very hard or be correct. And we have independent implementations in
C++ and Python that cross-check each other, si it's unlikely to be the former.
This commit is contained in:
Andrew Poelstra 2021-09-05 12:35:58 +00:00
commit 6387aaf765
17 changed files with 1795 additions and 48 deletions
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26
src/pubkey.cpp
View file

@ -186,12 +186,20 @@ bool XOnlyPubKey::IsFullyValid() const
return secp256k1_xonly_pubkey_parse(secp256k1_context_verify, &pubkey, m_keydata.data());
}
bool XOnlyPubKey::VerifySchnorr(const uint256& msg, Span<const unsigned char> sigbytes) const
bool XOnlyPubKey::VerifySchnorr(const Span<const unsigned char> msg, Span<const unsigned char> sigbytes) const
{
assert(sigbytes.size() == 64);
secp256k1_xonly_pubkey pubkey;
if (!secp256k1_xonly_pubkey_parse(secp256k1_context_verify, &pubkey, m_keydata.data())) return false;
return secp256k1_schnorrsig_verify(secp256k1_context_verify, sigbytes.data(), msg.begin(), 32, &pubkey);
return secp256k1_schnorrsig_verify(secp256k1_context_verify, sigbytes.data(), msg.data(), msg.size(), &pubkey);
}
// ELEMENTS: this is preserved from an old version of the Taproot code for use in OP_TWEAKVERIFY
bool XOnlyPubKey::CheckPayToContract(const XOnlyPubKey& base, const uint256& hash, bool parity) const
{
secp256k1_xonly_pubkey base_point;
if (!secp256k1_xonly_pubkey_parse(secp256k1_context_verify, &base_point, base.data())) return false;
return secp256k1_xonly_pubkey_tweak_add_check(secp256k1_context_verify, m_keydata.begin(), parity, &base_point, hash.begin());
}
static const CHashWriter HASHER_TAPTWEAK_ELEMENTS = TaggedHash("TapTweak/elements");
@ -215,6 +223,18 @@ bool XOnlyPubKey::CheckTapTweak(const XOnlyPubKey& internal, const uint256& merk
return secp256k1_xonly_pubkey_tweak_add_check(secp256k1_context_verify, m_keydata.begin(), parity, &internal_key, tweak.begin());
}
bool CPubKey::TweakMulVerify(const CPubKey& untweaked, const uint256& tweak) const
{
assert(this->IsCompressed());
secp256k1_pubkey pk;
if (!secp256k1_ec_pubkey_parse(secp256k1_context_verify, &pk, untweaked.data(), untweaked.size())) return false;
if (!secp256k1_ec_pubkey_tweak_mul(secp256k1_context_verify, &pk, tweak.data())) return false;
unsigned char out_pk[CPubKey::COMPRESSED_SIZE];
size_t out_len = CPubKey::COMPRESSED_SIZE;
if (!secp256k1_ec_pubkey_serialize(secp256k1_context_verify, out_pk, &out_len, &pk, SECP256K1_EC_COMPRESSED)) return false;
return *this == CPubKey(out_pk, out_pk + out_len);
}
std::optional<std::pair<XOnlyPubKey, bool>> XOnlyPubKey::CreateTapTweak(const uint256* merkle_root) const
{
secp256k1_xonly_pubkey base_point;
@ -226,7 +246,7 @@ std::optional<std::pair<XOnlyPubKey, bool>> XOnlyPubKey::CreateTapTweak(const ui
std::pair<XOnlyPubKey, bool> ret;
secp256k1_xonly_pubkey out_xonly;
if (!secp256k1_xonly_pubkey_from_pubkey(secp256k1_context_verify, &out_xonly, &parity, &out)) return std::nullopt;
secp256k1_xonly_pubkey_serialize(secp256k1_context_verify, ret.first.begin(), &out_xonly);
secp256k1_xonly_pubkey_serialize(secp256k1_context_verify, ret.first.data(), &out_xonly);
assert(parity == 0 || parity == 1);
ret.second = parity;
return ret;