// 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>
/**
* CPrivKey is a serialized private key, with all parameters included
* (SIZE bytes)
*/
typedef std::vector<unsigned char, secure_allocator<unsigned char> > CPrivKey;
/** Size of ECDH shared secrets. */
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>;
/** An encapsulated private key. */
class CKey
{
public:
/**
* secp256k1:
*/
static const unsigned int SIZE = 279;
static const unsigned int COMPRESSED_SIZE = 214;
/**
* see www.keylength.com
* script supports up to 75 for single byte push
*/
static_assert(
SIZE >= COMPRESSED_SIZE,
"COMPRESSED_SIZE is larger than SIZE");
private:
/** Internal data container for private key material. */
using KeyType = std::array<unsigned char, 32>;
//! Whether the public key corresponding to this private key is (to be) compressed.
bool fCompressed{false};
//! The actual byte data. nullptr for invalid keys.
secure_unique_ptr<KeyType> keydata;
//! Check whether the 32-byte array pointed to by vch is valid 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 (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;
}
//! Initialize using begin and end iterators to byte data.
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(&pbegin[0])) {
MakeKeyData();
memcpy(keydata->data(), (unsigned char*)&pbegin[0], keydata->size());
fCompressed = fCompressedIn;
} else {
ClearKeyData();
}
}
//! Simple read-only vector-like interface.
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 unsigned char* begin() const { return keydata ? keydata->data() : nullptr; }
const unsigned char* end() const { return begin() + size(); }
//! Check whether this private key is valid.
bool IsValid() const { return !!keydata; }
//! Check whether the public key corresponding to this private key is (to be) compressed.
bool IsCompressed() const { return fCompressed; }
//! Generate a new private key using a cryptographic PRNG.
void MakeNewKey(bool fCompressed);
//! Negate private key
bool Negate();
/**
* Convert the private key to a CPrivKey (serialized OpenSSL private key data).
* This is expensive.
*/
CPrivKey GetPrivKey() const;
/**
* Compute the public key from a private key.
* This is expensive.
*/
CPubKey GetPubKey() const;
/**
* Create a DER-serialized signature.
* The test_case parameter tweaks the deterministic nonce.
*/
bool Sign(const uint256& hash, std::vector<unsigned char>& vchSig, bool grind = true, uint32_t test_case = 0) const;
/**
* Create a compact signature (65 bytes), which allows reconstructing the used public key.
* The format is one header byte, followed by two times 32 bytes for the serialized r and s values.
* The header byte: 0x1B = first key with even y, 0x1C = first key with odd y,
* 0x1D = second key with even y, 0x1E = second key with odd y,
* add 0x04 for compressed keys.
*/
bool SignCompact(const uint256& hash, std::vector<unsigned char>& vchSig) const;
/**
* Create a BIP-340 Schnorr signature, for the xonly-pubkey corresponding to *this,
* optionally tweaked by *merkle_root. Additional nonce entropy is provided through
* aux.
*
* merkle_root is used to optionally perform tweaking of the private key, as specified
* in BIP341:
* - If merkle_root == nullptr: no tweaking is done, sign with key directly (this is
* used for signatures in BIP342 script).
* - If merkle_root->IsNull(): sign with key + H_TapTweak(pubkey) (this is used for
* key path spending when no scripts are present).
* - Otherwise: sign with key + H_TapTweak(pubkey || *merkle_root)
* (this is used for key path spending, with specific
* Merkle root of the script tree).
*/
bool SignSchnorr(const uint256& hash, Span<unsigned char> sig, const uint256* merkle_root, const uint256& aux) const;
//! Derive BIP32 child key.
[[nodiscard]] bool Derive(CKey& keyChild, ChainCode &ccChild, unsigned int nChild, const ChainCode& cc) const;
/**
* Verify thoroughly whether a private key and a public key match.
* This is done using a different mechanism than just regenerating it.
*/
bool VerifyPubKey(const CPubKey& vchPubKey) const;
//! Load private key and check that public key matches.
bool Load(const CPrivKey& privkey, const CPubKey& vchPubKey, bool fSkipCheck);
/** Create an ellswift-encoded public key for this key, with specified entropy.
*
* entropy must be a 32-byte span with additional entropy to use in the encoding. Every
* public key has ~2^256 different encodings, and this function will deterministically pick
* one of them, based on entropy. Note that even without truly random entropy, the
* resulting encoding will be indistinguishable from uniform to any adversary who does not
* know the private key (because the private key itself is always used as entropy as well).
*/
EllSwiftPubKey EllSwiftCreate(Span<const std::byte> entropy) const;
/** Compute a BIP324-style ECDH shared secret.
*
* - their_ellswift: EllSwiftPubKey that was received from the other side.
* - our_ellswift: EllSwiftPubKey that was sent to the other side (must have been generated
* from *this using EllSwiftCreate()).
* - initiating: whether we are the initiating party (true) or responding party (false).
*/
ECDHSecret ComputeBIP324ECDHSecret(const EllSwiftPubKey& their_ellswift,
const EllSwiftPubKey& our_ellswift,
bool initiating) const;
};
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;
}
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);
};
/** Initialize the elliptic curve support. May not be called twice without calling ECC_Stop first. */
void ECC_Start();
/** Deinitialize the elliptic curve support. No-op if ECC_Start wasn't called first. */
void ECC_Stop();
/** Check that required EC support is available at runtime. */
bool ECC_InitSanityCheck();
#endif // BITCOIN_KEY_H