key.h

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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2022 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.

#ifndef BITCOIN_KEY_H
#define BITCOIN_KEY_H

#include <pubkey.h>
#include <serialize.h>
#include <support/allocators/secure.h>
#include <uint256.h>

#include <stdexcept>
#include <vector>


typedef std::vector<unsigned char, secure_allocator<unsigned char> > CPrivKey;

constexpr static size_t ECDH_SECRET_SIZE = CSHA256::OUTPUT_SIZE;

// Used to represent ECDH shared secret (ECDH_SECRET_SIZE bytes)
using ECDHSecret = std::array<std::byte, ECDH_SECRET_SIZE>;

class KeyPair;

class CKey
{
public:
    static const unsigned int SIZE            = 279;
    static const unsigned int COMPRESSED_SIZE = 214;
    static_assert(
        SIZE >= COMPRESSED_SIZE,
        "COMPRESSED_SIZE is larger than SIZE");

private:
    using KeyType = std::array<unsigned char, 32>;

    bool fCompressed{false};

    secure_unique_ptr<KeyType> keydata;

    bool static Check(const unsigned char* vch);

    void MakeKeyData()
    {
        if (!keydata) keydata = make_secure_unique<KeyType>();
    }

    void ClearKeyData()
    {
        keydata.reset();
    }

public:
    CKey() noexcept = default;
    CKey(CKey&&) noexcept = default;
    CKey& operator=(CKey&&) noexcept = default;

    CKey& operator=(const CKey& other)
    {
        if (this != &other) {
            if (other.keydata) {
                MakeKeyData();
                *keydata = *other.keydata;
            } else {
                ClearKeyData();
            }
            fCompressed = other.fCompressed;
        }
        return *this;
    }

    CKey(const CKey& other) { *this = other; }

    friend bool operator==(const CKey& a, const CKey& b)
    {
        return a.fCompressed == b.fCompressed &&
            a.size() == b.size() &&
            memcmp(a.data(), b.data(), a.size()) == 0;
    }

    template <typename T>
    void Set(const T pbegin, const T pend, bool fCompressedIn)
    {
        if (size_t(pend - pbegin) != std::tuple_size_v<KeyType>) {
            ClearKeyData();
        } else if (Check(UCharCast(&pbegin[0]))) {
            MakeKeyData();
            memcpy(keydata->data(), (unsigned char*)&pbegin[0], keydata->size());
            fCompressed = fCompressedIn;
        } else {
            ClearKeyData();
        }
    }

    unsigned int size() const { return keydata ? keydata->size() : 0; }
    const std::byte* data() const { return keydata ? reinterpret_cast<const std::byte*>(keydata->data()) : nullptr; }
    const std::byte* begin() const { return data(); }
    const std::byte* end() const { return data() + size(); }

    bool IsValid() const { return !!keydata; }

    bool IsCompressed() const { return fCompressed; }

    void MakeNewKey(bool fCompressed);

    CPrivKey GetPrivKey() const;

    CPubKey GetPubKey() const;

    bool Sign(const uint256& hash, std::vector<unsigned char>& vchSig, bool grind = true, uint32_t test_case = 0) const;

    bool SignCompact(const uint256& hash, std::vector<unsigned char>& vchSig) const;

    bool SignSchnorr(const uint256& hash, Span<unsigned char> sig, const uint256* merkle_root, const uint256& aux) const;

    [[nodiscard]] bool Derive(CKey& keyChild, ChainCode &ccChild, unsigned int nChild, const ChainCode& cc) const;

    bool VerifyPubKey(const CPubKey& vchPubKey) const;

    bool Load(const CPrivKey& privkey, const CPubKey& vchPubKey, bool fSkipCheck);

    EllSwiftPubKey EllSwiftCreate(Span<const std::byte> entropy) const;

    ECDHSecret ComputeBIP324ECDHSecret(const EllSwiftPubKey& their_ellswift,
                                       const EllSwiftPubKey& our_ellswift,
                                       bool initiating) const;
    KeyPair ComputeKeyPair(const uint256* merkle_root) const;
};

CKey GenerateRandomKey(bool compressed = true) noexcept;

struct CExtKey {
    unsigned char nDepth;
    unsigned char vchFingerprint[4];
    unsigned int nChild;
    ChainCode chaincode;
    CKey key;

    friend bool operator==(const CExtKey& a, const CExtKey& b)
    {
        return a.nDepth == b.nDepth &&
            memcmp(a.vchFingerprint, b.vchFingerprint, sizeof(vchFingerprint)) == 0 &&
            a.nChild == b.nChild &&
            a.chaincode == b.chaincode &&
            a.key == b.key;
    }

    CExtKey() = default;
    CExtKey(const CExtPubKey& xpub, const CKey& key_in) : nDepth(xpub.nDepth), nChild(xpub.nChild), chaincode(xpub.chaincode), key(key_in)
    {
        std::copy(xpub.vchFingerprint, xpub.vchFingerprint + sizeof(xpub.vchFingerprint), vchFingerprint);
    }

    void Encode(unsigned char code[BIP32_EXTKEY_SIZE]) const;
    void Decode(const unsigned char code[BIP32_EXTKEY_SIZE]);
    [[nodiscard]] bool Derive(CExtKey& out, unsigned int nChild) const;
    CExtPubKey Neuter() const;
    void SetSeed(Span<const std::byte> seed);
};

class KeyPair
{
public:
    KeyPair() noexcept = default;
    KeyPair(KeyPair&&) noexcept = default;
    KeyPair& operator=(KeyPair&&) noexcept = default;
    KeyPair& operator=(const KeyPair& other)
    {
        if (this != &other) {
            if (other.m_keypair) {
                MakeKeyPairData();
                *m_keypair = *other.m_keypair;
            } else {
                ClearKeyPairData();
            }
        }
        return *this;
    }

    KeyPair(const KeyPair& other) { *this = other; }

    friend KeyPair CKey::ComputeKeyPair(const uint256* merkle_root) const;
    [[nodiscard]] bool SignSchnorr(const uint256& hash, Span<unsigned char> sig, const uint256& aux) const;

    bool IsValid() const { return !!m_keypair; }

private:
    KeyPair(const CKey& key, const uint256* merkle_root);

    using KeyType = std::array<unsigned char, 96>;
    secure_unique_ptr<KeyType> m_keypair;

    void MakeKeyPairData()
    {
        if (!m_keypair) m_keypair = make_secure_unique<KeyType>();
    }

    void ClearKeyPairData()
    {
        m_keypair.reset();
    }
};

bool ECC_InitSanityCheck();

class ECC_Context
{
public:
    ECC_Context();
    ~ECC_Context();
};

#endif // BITCOIN_KEY_H