crypter.h

// Copyright (c) 2009-2012 The Bitcoin Developers
// Distributed under the MIT/X11 software license, see the accompanying
// file COPYING or https://opensource.org/licenses/mit-license.php.

#ifndef BITCOIN_CRYPTER_H
#define BITCOIN_CRYPTER_H

#include "support/allocators/secure.h" /* for SecureString */
#include "key.h"

const unsigned int WALLET_CRYPTO_KEY_SIZE = 32;
const unsigned int WALLET_CRYPTO_SALT_SIZE = 8;

/*
Private key encryption is done based on a CMasterKey,
which holds a salt and random encryption key.

CMasterKeys are encrypted using AES-256-CBC using a key
derived using derivation method nDerivationMethod
(0 == EVP_sha512()) and derivation iterations nDeriveIterations.
vchOtherDerivationParameters is provided for alternative algorithms
which may require more parameters (such as scrypt).

Wallet Private Keys are then encrypted using AES-256-CBC
with the double-sha256 of the public key as the IV, and the
master key's key as the encryption key (see keystore.[ch]).
*/

/** Master key for wallet encryption */
class CMasterKey
{
public:
    std::vector<unsigned char> vchCryptedKey;
    std::vector<unsigned char> vchSalt;
    // 0 = EVP_sha512()
    // 1 = scrypt()
    unsigned int nDerivationMethod;
    unsigned int nDeriveIterations;
    // Use this for more parameters to key derivation,
    // such as the various parameters to scrypt
    std::vector<unsigned char> vchOtherDerivationParameters;

    ADD_SERIALIZE_METHODS;

    template <typename Stream, typename Operation>
    inline void SerializationOp(Stream& s, Operation ser_action)
    {
        READWRITE(vchCryptedKey);
        READWRITE(vchSalt);
        READWRITE(nDerivationMethod);
        READWRITE(nDeriveIterations);
        READWRITE(vchOtherDerivationParameters);
    }

    CMasterKey()
    {
        // 25000 rounds is just under 0.1 seconds on a 1.86 GHz Pentium M
        // ie slightly lower than the lowest hardware we need bother supporting
        nDeriveIterations = 25000;
        nDerivationMethod = 1;
        vchOtherDerivationParameters = std::vector<unsigned char>(0);
    }

    CMasterKey(unsigned int nDerivationMethodIndex)
    {
        switch (nDerivationMethodIndex)
        {
            case 0: // sha512
            default:
                nDeriveIterations = 25000;
                nDerivationMethod = 0;
                vchOtherDerivationParameters = std::vector<unsigned char>(0);
            break;

            case 1: // scrypt+sha512
                nDeriveIterations = 10000;
                nDerivationMethod = 1;
                vchOtherDerivationParameters = std::vector<unsigned char>(0);
            break;
        }
    }

};

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

/** Encryption/decryption context with key information */
class CCrypter
{
private:
    std::vector<unsigned char, secure_allocator<unsigned char>> vchKey;
    std::vector<unsigned char, secure_allocator<unsigned char>> vchIV;
    bool fKeySet;

public:
    bool SetKeyFromPassphrase(const SecureString &strKeyData, const std::vector<unsigned char>& chSalt, const unsigned int nRounds, const unsigned int nDerivationMethod);
    bool Encrypt(const CKeyingMaterial& vchPlaintext, std::vector<unsigned char> &vchCiphertext) const;
    bool Decrypt(const std::vector<unsigned char>& vchCiphertext, CKeyingMaterial& vchPlaintext) const;
    bool SetKey(const CKeyingMaterial& chNewKey, const std::vector<unsigned char>& chNewIV);

    void CleanKey()
    {
        memory_cleanse(vchKey.data(), vchKey.size());
        memory_cleanse(vchIV.data(), vchIV.size());
        fKeySet = false;
    }

    CCrypter()
    {
        fKeySet = false;
        vchKey.resize(WALLET_CRYPTO_KEY_SIZE);
        // TODO: Bitcoin uses an IV size of 16 defined by WALLET_CRYPTO_IV_SIZE.
        vchIV.resize(WALLET_CRYPTO_KEY_SIZE);
    }

    ~CCrypter()
    {
        CleanKey();
    }
};


bool EncryptSecret(const CKeyingMaterial& vMasterKey, const CKeyingMaterial &vchPlaintext, const uint256& nIV, std::vector<unsigned char> &vchCiphertext);
bool DecryptSecret(const CKeyingMaterial& vMasterKey, const std::vector<unsigned char> &vchCiphertext, const uint256& nIV, CKeyingMaterial& vchPlaintext);
bool DecryptKey(const CKeyingMaterial& vMasterKey, const std::vector<unsigned char>& vchCryptedSecret, const CPubKey& vchPubKey, CKey& key);

#endif // BITCOIN_CRYPTER_H