303 lines
9 KiB
C++
303 lines
9 KiB
C++
// Copyright (c) 2009-2016 The Bitcoin Core developers
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// Distributed under the MIT software license, see the accompanying
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// file COPYING or http://www.opensource.org/licenses/mit-license.php.
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#include "pubkey.h"
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#include <secp256k1.h>
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#include <secp256k1_recovery.h>
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namespace
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{
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/* Global secp256k1_context object used for verification. */
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secp256k1_context* secp256k1_context_verify = NULL;
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}
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/** This function is taken from the libsecp256k1 distribution and implements
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* DER parsing for ECDSA signatures, while supporting an arbitrary subset of
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* format violations.
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*
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* Supported violations include negative integers, excessive padding, garbage
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* at the end, and overly long length descriptors. This is safe to use in
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* Bitcoin because since the activation of BIP66, signatures are verified to be
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* strict DER before being passed to this module, and we know it supports all
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* violations present in the blockchain before that point.
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*/
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static int ecdsa_signature_parse_der_lax(const secp256k1_context* ctx, secp256k1_ecdsa_signature* sig, const unsigned char *input, size_t inputlen) {
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size_t rpos, rlen, spos, slen;
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size_t pos = 0;
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size_t lenbyte;
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unsigned char tmpsig[64] = {0};
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int overflow = 0;
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/* Hack to initialize sig with a correctly-parsed but invalid signature. */
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secp256k1_ecdsa_signature_parse_compact(ctx, sig, tmpsig);
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/* Sequence tag byte */
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if (pos == inputlen || input[pos] != 0x30) {
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return 0;
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}
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pos++;
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/* Sequence length bytes */
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if (pos == inputlen) {
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return 0;
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}
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lenbyte = input[pos++];
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if (lenbyte & 0x80) {
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lenbyte -= 0x80;
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if (pos + lenbyte > inputlen) {
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return 0;
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}
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pos += lenbyte;
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}
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/* Integer tag byte for R */
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if (pos == inputlen || input[pos] != 0x02) {
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return 0;
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}
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pos++;
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/* Integer length for R */
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if (pos == inputlen) {
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return 0;
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}
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lenbyte = input[pos++];
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if (lenbyte & 0x80) {
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lenbyte -= 0x80;
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if (pos + lenbyte > inputlen) {
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return 0;
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}
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while (lenbyte > 0 && input[pos] == 0) {
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pos++;
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lenbyte--;
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}
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if (lenbyte >= sizeof(size_t)) {
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return 0;
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}
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rlen = 0;
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while (lenbyte > 0) {
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rlen = (rlen << 8) + input[pos];
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pos++;
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lenbyte--;
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}
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} else {
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rlen = lenbyte;
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}
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if (rlen > inputlen - pos) {
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return 0;
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}
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rpos = pos;
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pos += rlen;
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/* Integer tag byte for S */
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if (pos == inputlen || input[pos] != 0x02) {
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return 0;
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}
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pos++;
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/* Integer length for S */
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if (pos == inputlen) {
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return 0;
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}
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lenbyte = input[pos++];
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if (lenbyte & 0x80) {
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lenbyte -= 0x80;
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if (pos + lenbyte > inputlen) {
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return 0;
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}
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while (lenbyte > 0 && input[pos] == 0) {
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pos++;
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lenbyte--;
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}
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if (lenbyte >= sizeof(size_t)) {
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return 0;
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}
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slen = 0;
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while (lenbyte > 0) {
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slen = (slen << 8) + input[pos];
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pos++;
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lenbyte--;
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}
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} else {
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slen = lenbyte;
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}
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if (slen > inputlen - pos) {
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return 0;
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}
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spos = pos;
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pos += slen;
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/* Ignore leading zeroes in R */
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while (rlen > 0 && input[rpos] == 0) {
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rlen--;
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rpos++;
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}
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/* Copy R value */
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if (rlen > 32) {
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overflow = 1;
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} else {
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memcpy(tmpsig + 32 - rlen, input + rpos, rlen);
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}
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/* Ignore leading zeroes in S */
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while (slen > 0 && input[spos] == 0) {
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slen--;
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spos++;
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}
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/* Copy S value */
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if (slen > 32) {
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overflow = 1;
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} else {
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memcpy(tmpsig + 64 - slen, input + spos, slen);
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}
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if (!overflow) {
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overflow = !secp256k1_ecdsa_signature_parse_compact(ctx, sig, tmpsig);
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}
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if (overflow) {
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/* Overwrite the result again with a correctly-parsed but invalid
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signature if parsing failed. */
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memset(tmpsig, 0, 64);
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secp256k1_ecdsa_signature_parse_compact(ctx, sig, tmpsig);
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}
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return 1;
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}
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bool CPubKey::Verify(const uint256 &hash, const std::vector<unsigned char>& vchSig) const {
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if (!IsValid())
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return false;
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secp256k1_pubkey pubkey;
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secp256k1_ecdsa_signature sig;
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if (!secp256k1_ec_pubkey_parse(secp256k1_context_verify, &pubkey, &(*this)[0], size())) {
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return false;
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}
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if (vchSig.size() == 0) {
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return false;
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}
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if (!ecdsa_signature_parse_der_lax(secp256k1_context_verify, &sig, &vchSig[0], vchSig.size())) {
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return false;
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}
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/* libsecp256k1's ECDSA verification requires lower-S signatures, which have
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* not historically been enforced in Bitcoin, so normalize them first. */
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secp256k1_ecdsa_signature_normalize(secp256k1_context_verify, &sig, &sig);
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return secp256k1_ecdsa_verify(secp256k1_context_verify, &sig, hash.begin(), &pubkey);
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}
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bool CPubKey::RecoverCompact(const uint256 &hash, const std::vector<unsigned char>& vchSig) {
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if (vchSig.size() != 65)
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return false;
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int recid = (vchSig[0] - 27) & 3;
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bool fComp = ((vchSig[0] - 27) & 4) != 0;
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secp256k1_pubkey pubkey;
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secp256k1_ecdsa_recoverable_signature sig;
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if (!secp256k1_ecdsa_recoverable_signature_parse_compact(secp256k1_context_verify, &sig, &vchSig[1], recid)) {
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return false;
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}
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if (!secp256k1_ecdsa_recover(secp256k1_context_verify, &pubkey, &sig, hash.begin())) {
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return false;
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}
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unsigned char pub[65];
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size_t publen = 65;
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secp256k1_ec_pubkey_serialize(secp256k1_context_verify, pub, &publen, &pubkey, fComp ? SECP256K1_EC_COMPRESSED : SECP256K1_EC_UNCOMPRESSED);
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Set(pub, pub + publen);
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return true;
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}
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bool CPubKey::IsFullyValid() const {
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if (!IsValid())
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return false;
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secp256k1_pubkey pubkey;
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return secp256k1_ec_pubkey_parse(secp256k1_context_verify, &pubkey, &(*this)[0], size());
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}
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bool CPubKey::Decompress() {
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if (!IsValid())
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return false;
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secp256k1_pubkey pubkey;
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if (!secp256k1_ec_pubkey_parse(secp256k1_context_verify, &pubkey, &(*this)[0], size())) {
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return false;
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}
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unsigned char pub[65];
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size_t publen = 65;
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secp256k1_ec_pubkey_serialize(secp256k1_context_verify, pub, &publen, &pubkey, SECP256K1_EC_UNCOMPRESSED);
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Set(pub, pub + publen);
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return true;
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}
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bool CPubKey::Derive(CPubKey& pubkeyChild, ChainCode &ccChild, unsigned int nChild, const ChainCode& cc) const {
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assert(IsValid());
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assert((nChild >> 31) == 0);
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assert(begin() + 33 == end());
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unsigned char out[64];
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BIP32Hash(cc, nChild, *begin(), begin()+1, out);
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memcpy(ccChild.begin(), out+32, 32);
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secp256k1_pubkey pubkey;
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if (!secp256k1_ec_pubkey_parse(secp256k1_context_verify, &pubkey, &(*this)[0], size())) {
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return false;
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}
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if (!secp256k1_ec_pubkey_tweak_add(secp256k1_context_verify, &pubkey, out)) {
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return false;
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}
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unsigned char pub[33];
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size_t publen = 33;
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secp256k1_ec_pubkey_serialize(secp256k1_context_verify, pub, &publen, &pubkey, SECP256K1_EC_COMPRESSED);
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pubkeyChild.Set(pub, pub + publen);
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return true;
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}
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void CExtPubKey::Encode(unsigned char code[BIP32_EXTKEY_SIZE]) const {
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code[0] = nDepth;
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memcpy(code+1, vchFingerprint, 4);
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code[5] = (nChild >> 24) & 0xFF; code[6] = (nChild >> 16) & 0xFF;
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code[7] = (nChild >> 8) & 0xFF; code[8] = (nChild >> 0) & 0xFF;
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memcpy(code+9, chaincode.begin(), 32);
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assert(pubkey.size() == 33);
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memcpy(code+41, pubkey.begin(), 33);
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}
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void CExtPubKey::Decode(const unsigned char code[BIP32_EXTKEY_SIZE]) {
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nDepth = code[0];
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memcpy(vchFingerprint, code+1, 4);
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nChild = (code[5] << 24) | (code[6] << 16) | (code[7] << 8) | code[8];
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memcpy(chaincode.begin(), code+9, 32);
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pubkey.Set(code+41, code+BIP32_EXTKEY_SIZE);
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}
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bool CExtPubKey::Derive(CExtPubKey &out, unsigned int _nChild) const {
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out.nDepth = nDepth + 1;
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CKeyID id = pubkey.GetID();
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memcpy(&out.vchFingerprint[0], &id, 4);
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out.nChild = _nChild;
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return pubkey.Derive(out.pubkey, out.chaincode, _nChild, chaincode);
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}
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/* static */ bool CPubKey::CheckLowS(const std::vector<unsigned char>& vchSig) {
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secp256k1_ecdsa_signature sig;
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if (!ecdsa_signature_parse_der_lax(secp256k1_context_verify, &sig, &vchSig[0], vchSig.size())) {
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return false;
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}
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return (!secp256k1_ecdsa_signature_normalize(secp256k1_context_verify, NULL, &sig));
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}
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/* static */ int ECCVerifyHandle::refcount = 0;
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ECCVerifyHandle::ECCVerifyHandle()
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{
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if (refcount == 0) {
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assert(secp256k1_context_verify == NULL);
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secp256k1_context_verify = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY);
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assert(secp256k1_context_verify != NULL);
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}
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refcount++;
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}
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ECCVerifyHandle::~ECCVerifyHandle()
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{
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refcount--;
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if (refcount == 0) {
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assert(secp256k1_context_verify != NULL);
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secp256k1_context_destroy(secp256k1_context_verify);
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secp256k1_context_verify = NULL;
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}
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}
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