pubkey.cpp

// Copyright (c) 2009-2014 The Bitcoin Core developers
// Copyright (c) 2017 The Zcash developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include "pubkey.h"

#include <secp256k1.h>
//#include <secp256k1_recovery.h>

namespace
{
/* Global secp256k1_context object used for verification. */
secp256k1_context* secp256k1_context_verify = NULL;
}


bool CPubKey::Verify(const uint256 &hash, const std::vector<unsigned char>& vchSig) const {
    if (!IsValid())
        return false;
    secp256k1_pubkey pubkey;
    secp256k1_ecdsa_signature sig;
    if (!secp256k1_ec_pubkey_parse(secp256k1_context_verify, &pubkey, &(*this)[0], size())) {
        return false;
    }
    if (vchSig.size() == 0) {
        return false;
    }
    /* Zcash, unlike Bitcoin, has always enforced strict DER signatures. */
    if (!secp256k1_ecdsa_signature_parse_der(secp256k1_context_verify, &sig, &vchSig[0], vchSig.size())) {
        return false;
    }
    /* libsecp256k1's ECDSA verification requires lower-S signatures, which have
     * not historically been enforced in Bitcoin or Zcash, so normalize them first. */
    secp256k1_ecdsa_signature_normalize(secp256k1_context_verify, &sig, &sig);
    return secp256k1_ecdsa_verify(secp256k1_context_verify, &sig, hash.begin(), &pubkey);
}
//
//bool CPubKey::RecoverCompact(const uint256 &hash, const std::vector<unsigned char>& vchSig) {
//    if (vchSig.size() != COMPACT_SIGNATURE_SIZE)
//        return false;
//    int recid = (vchSig[0] - 27) & 3;
//    bool fComp = ((vchSig[0] - 27) & 4) != 0;
//    secp256k1_pubkey pubkey;
//    secp256k1_ecdsa_recoverable_signature sig;
//    if (!secp256k1_ecdsa_recoverable_signature_parse_compact(secp256k1_context_verify, &sig, &vchSig[1], recid)) {
//        return false;
//    }
//    if (!secp256k1_ecdsa_recover(secp256k1_context_verify, &pubkey, &sig, hash.begin())) {
//        return false;
//    }
//    unsigned char pub[PUBLIC_KEY_SIZE];
//    size_t publen = PUBLIC_KEY_SIZE;
//    secp256k1_ec_pubkey_serialize(secp256k1_context_verify, pub, &publen, &pubkey, fComp ? SECP256K1_EC_COMPRESSED : SECP256K1_EC_UNCOMPRESSED);
//    Set(pub, pub + publen);
//    return true;
//}

bool CPubKey::IsFullyValid() const {
    if (!IsValid())
        return false;
    secp256k1_pubkey pubkey;
    return secp256k1_ec_pubkey_parse(secp256k1_context_verify, &pubkey, &(*this)[0], size());
}

bool CPubKey::Decompress() {
    if (!IsValid())
        return false;
    secp256k1_pubkey pubkey;
    if (!secp256k1_ec_pubkey_parse(secp256k1_context_verify, &pubkey, &(*this)[0], size())) {
        return false;
    }
    unsigned char pub[PUBLIC_KEY_SIZE];
    size_t publen = PUBLIC_KEY_SIZE;
    secp256k1_ec_pubkey_serialize(secp256k1_context_verify, pub, &publen, &pubkey, SECP256K1_EC_UNCOMPRESSED);
    Set(pub, pub + publen);
    return true;
}

bool CPubKey::Derive(CPubKey& pubkeyChild, ChainCode &ccChild, unsigned int nChild, const ChainCode& cc) const {
    assert(IsValid());
    assert((nChild >> 31) == 0);
    assert(size() == COMPRESSED_PUBLIC_KEY_SIZE);
    unsigned char out[64];
    BIP32Hash(cc, nChild, *begin(), begin()+1, out);
    memcpy(ccChild.begin(), out+32, 32);
    secp256k1_pubkey pubkey;
    if (!secp256k1_ec_pubkey_parse(secp256k1_context_verify, &pubkey, &(*this)[0], size())) {
        return false;
    }
    if (!secp256k1_ec_pubkey_tweak_add(secp256k1_context_verify, &pubkey, out)) {
        return false;
    }
    unsigned char pub[COMPRESSED_PUBLIC_KEY_SIZE];
    size_t publen = COMPRESSED_PUBLIC_KEY_SIZE;
    secp256k1_ec_pubkey_serialize(secp256k1_context_verify, pub, &publen, &pubkey, SECP256K1_EC_COMPRESSED);
    pubkeyChild.Set(pub, pub + publen);
    return true;
}

void CExtPubKey::Encode(unsigned char code[74]) const {
    code[0] = nDepth;
    memcpy(code+1, vchFingerprint, 4);
    code[5] = (nChild >> 24) & 0xFF; code[6] = (nChild >> 16) & 0xFF;
    code[7] = (nChild >>  8) & 0xFF; code[8] = (nChild >>  0) & 0xFF;
    memcpy(code+9, chaincode.begin(), 32);
    assert(pubkey.size() == CPubKey::COMPRESSED_PUBLIC_KEY_SIZE);
    memcpy(code+41, pubkey.begin(), CPubKey::COMPRESSED_PUBLIC_KEY_SIZE);
}

void CExtPubKey::Decode(const unsigned char code[74]) {
    nDepth = code[0];
    memcpy(vchFingerprint, code+1, 4);
    nChild = (code[5] << 24) | (code[6] << 16) | (code[7] << 8) | code[8];
    memcpy(chaincode.begin(), code+9, 32);
    pubkey.Set(code+41, code+74);
}

bool CExtPubKey::Derive(CExtPubKey &out, unsigned int nChild) const {
    out.nDepth = nDepth + 1;
    CKeyID id = pubkey.GetID();
    memcpy(&out.vchFingerprint[0], &id, 4);
    out.nChild = nChild;
    return pubkey.Derive(out.pubkey, out.chaincode, nChild, chaincode);
}

/* static */ bool CPubKey::CheckLowS(const std::vector<unsigned char>& vchSig) {
    secp256k1_ecdsa_signature sig;

    /* Zcash, unlike Bitcoin, has always enforced strict DER signatures. */
    if (!secp256k1_ecdsa_signature_parse_der(secp256k1_context_verify, &sig, &vchSig[0], vchSig.size())) {
        return false;
    }
    return (!secp256k1_ecdsa_signature_normalize(secp256k1_context_verify, NULL, &sig));
}

/* static */ int ECCVerifyHandle::refcount = 0;

ECCVerifyHandle::ECCVerifyHandle()
{
    if (refcount == 0) {
        assert(secp256k1_context_verify == NULL);
        secp256k1_context_verify = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY);
        assert(secp256k1_context_verify != NULL);
    }
    refcount++;
}

ECCVerifyHandle::~ECCVerifyHandle()
{
    refcount--;
    if (refcount == 0) {
        assert(secp256k1_context_verify != NULL);
        secp256k1_context_destroy(secp256k1_context_verify);
        secp256k1_context_verify = NULL;
    }
}