key.cpp

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// Copyright (c) 2009-2014 The Bitcoin developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
#include "key.h"
 
#include "crypto/hmac_sha512.h"
#include "crypto/rfc6979_hmac_sha256.h"
#include "eccryptoverify.h"
#include "pubkey.h"
#include "random.h"
 
#include "ecwrapper.h"
#include <secp256k1.h>
 
namespace
{
class CSecp256k1Init
{
public:
    CSecp256k1Init()
    {
        secp256k1_start(SECP256K1_START_SIGN | SECP256K1_START_VERIFY);
    }
    ~CSecp256k1Init()
    {
        secp256k1_stop();
    }
};
static CSecp256k1Init instance_of_csecp256k1;
 
} // anon namespace
 
bool CKey::Check(const unsigned char* vch)
{
    return eccrypto::Check(vch);
}
 
void CKey::MakeNewKey(bool fCompressedIn)
{
    do {
        GetStrongRandBytes(vch, sizeof(vch));
    } while (!Check(vch));
    fValid = true;
    fCompressed = fCompressedIn;
}
 
bool CKey::SetPrivKey(const CPrivKey& privkey, bool fCompressedIn)
{
    if (!secp256k1_ec_privkey_import((unsigned char*)begin(), &privkey[0], privkey.size()))
        return false;
    fCompressed = fCompressedIn;
    fValid = true;
    return true;
}
 
uint256 CKey::GetPrivKey_256()
{
    void* key = &vch;
    uint256* key_256 = (uint256*)key;
 
    return *key_256;
}
 
CPrivKey CKey::GetPrivKey() const
{
    assert(fValid);
    CPrivKey privkey;
    int privkeylen, ret;
    privkey.resize(279);
    privkeylen = 279;
    ret = secp256k1_ec_privkey_export(begin(), (unsigned char*)&privkey[0], &privkeylen, fCompressed);
    assert(ret);
    privkey.resize(privkeylen);
    return privkey;
}
 
CPubKey CKey::GetPubKey() const
{
    assert(fValid);
    CPubKey result;
    int clen = 65;
    int ret = secp256k1_ec_pubkey_create((unsigned char*)result.begin(), &clen, begin(), fCompressed);
    assert((int)result.size() == clen);
    assert(ret);
    assert(result.IsValid());
    return result;
}
 
bool CKey::Sign(const uint256& hash, std::vector<unsigned char>& vchSig, uint32_t test_case) const
{
    if (!fValid)
        return false;
    vchSig.resize(72);
    RFC6979_HMAC_SHA256 prng(begin(), 32, (unsigned char*)&hash, 32);
    do {
        uint256 nonce;
        prng.Generate((unsigned char*)&nonce, 32);
        nonce += test_case;
        int nSigLen = 72;
        int ret = secp256k1_ecdsa_sign((const unsigned char*)&hash, 32, (unsigned char*)&vchSig[0], &nSigLen, begin(), (unsigned char*)&nonce);
        nonce = 0;
        if (ret) {
            vchSig.resize(nSigLen);
            return true;
        }
    } while (true);
}
 
bool CKey::VerifyPubKey(const CPubKey& pubkey) const
{
    if (pubkey.IsCompressed() != fCompressed) {
        return false;
    }
    unsigned char rnd[8];
    std::string str = "Bitcoin key verification\n";
    GetRandBytes(rnd, sizeof(rnd));
    uint256 hash;
    CHash256().Write((unsigned char*)str.data(), str.size()).Write(rnd, sizeof(rnd)).Finalize((unsigned char*)&hash);
    std::vector<unsigned char> vchSig;
    Sign(hash, vchSig);
    return pubkey.Verify(hash, vchSig);
}
 
bool CKey::SignCompact(const uint256& hash, std::vector<unsigned char>& vchSig) const
{
    if (!fValid)
        return false;
    vchSig.resize(65);
    int rec = -1;
    RFC6979_HMAC_SHA256 prng(begin(), 32, (unsigned char*)&hash, 32);
    do {
        uint256 nonce;
        prng.Generate((unsigned char*)&nonce, 32);
        int ret = secp256k1_ecdsa_sign_compact((const unsigned char*)&hash, 32, &vchSig[1], begin(), (unsigned char*)&nonce, &rec);
        nonce = 0;
        if (ret)
            break;
    } while (true);
    assert(rec != -1);
    vchSig[0] = 27 + rec + (fCompressed ? 4 : 0);
    return true;
}
 
bool CKey::Load(CPrivKey& privkey, CPubKey& vchPubKey, bool fSkipCheck = false)
{
    if (!secp256k1_ec_privkey_import((unsigned char*)begin(), &privkey[0], privkey.size()))
        return false;
    fCompressed = vchPubKey.IsCompressed();
    fValid = true;
 
    if (fSkipCheck)
        return true;
 
    return VerifyPubKey(vchPubKey);
}
 
bool CKey::Derive(CKey& keyChild, unsigned char ccChild[32], unsigned int nChild, const unsigned char cc[32]) const
{
    assert(IsValid());
    assert(IsCompressed());
    unsigned char out[64];
    LockObject(out);
    if ((nChild >> 31) == 0) {
        CPubKey pubkey = GetPubKey();
        assert(pubkey.begin() + 33 == pubkey.end());
        BIP32Hash(cc, nChild, *pubkey.begin(), pubkey.begin() + 1, out);
    } else {
        assert(begin() + 32 == end());
        BIP32Hash(cc, nChild, 0, begin(), out);
    }
    memcpy(ccChild, out + 32, 32);
    memcpy((unsigned char*)keyChild.begin(), begin(), 32);
    bool ret = secp256k1_ec_privkey_tweak_add((unsigned char*)keyChild.begin(), out);
    UnlockObject(out);
    keyChild.fCompressed = true;
    keyChild.fValid = ret;
    return ret;
}
 
bool CExtKey::Derive(CExtKey& out, unsigned int nChild) const
{
    out.nDepth = nDepth + 1;
    CKeyID id = key.GetPubKey().GetID();
    memcpy(&out.vchFingerprint[0], &id, 4);
    out.nChild = nChild;
    return key.Derive(out.key, out.vchChainCode, nChild, vchChainCode);
}
 
void CExtKey::SetMaster(const unsigned char* seed, unsigned int nSeedLen)
{
    static const unsigned char hashkey[] = {'p', 'r', 'c', 'y', 'c', 'o', 'i', 'n', ' ', 's', 'e', 'e', 'd'};
    unsigned char out[64];
    LockObject(out);
    CHMAC_SHA512(hashkey, sizeof(hashkey)).Write(seed, nSeedLen).Finalize(out);
    key.Set(&out[0], &out[32], true);
    memcpy(vchChainCode, &out[32], 32);
    UnlockObject(out);
    nDepth = 0;
    nChild = 0;
    memset(vchFingerprint, 0, sizeof(vchFingerprint));
}
 
CExtPubKey CExtKey::Neuter() const
{
    CExtPubKey ret;
    ret.nDepth = nDepth;
    memcpy(&ret.vchFingerprint[0], &vchFingerprint[0], 4);
    ret.nChild = nChild;
    ret.pubkey = key.GetPubKey();
    memcpy(&ret.vchChainCode[0], &vchChainCode[0], 32);
    return ret;
}
 
void CExtKey::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, vchChainCode, 32);
    code[41] = 0;
    assert(key.size() == 32);
    memcpy(code + 42, key.begin(), 32);
}
 
void CExtKey::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(vchChainCode, code + 9, 32);
    key.Set(code + 42, code + 74, true);
}
 
bool ECC_InitSanityCheck()
{
#if !defined(USE_SECP256K1)
    if (!CECKey::SanityCheck()) {
        return false;
    }
#endif
    CKey key;
    key.MakeNewKey(true);
    CPubKey pubkey = key.GetPubKey();
    return key.VerifyPubKey(pubkey);
}