bool tx_extra_message::decrypt(size_t index, const Crypto::PublicKey &txkey, const Crypto::SecretKey *recepient_secret_key, std::string &message) const {
size_t mlen = data.size();
if (mlen < TX_EXTRA_MESSAGE_CHECKSUM_SIZE) {
return false;
}
const char *buf;
std::unique_ptr<char[]> ptr;
if (recepient_secret_key != nullptr) {
ptr.reset(new char[mlen]);
assert(ptr);
message_key_data key_data;
if (!generate_key_derivation(txkey, *recepient_secret_key, key_data.derivation)) {
return false;
}
key_data.magic1 = 0x80;
key_data.magic2 = 0;
Hash h = cn_fast_hash(&key_data, sizeof(message_key_data));
uint64_t nonce = SWAP64LE(index);
chacha(10, data.data(), mlen, reinterpret_cast<uint8_t *>(&h), reinterpret_cast<uint8_t *>(&nonce), ptr.get());
buf = ptr.get();
} else {
buf = data.data();
}
mlen -= TX_EXTRA_MESSAGE_CHECKSUM_SIZE;
for (size_t i = 0; i < TX_EXTRA_MESSAGE_CHECKSUM_SIZE; i++) {
if (buf[mlen + i] != 0) {
return false;
}
}
message.assign(buf, mlen);
return true;
}
void ChaCha::set_iv(const byte iv[], size_t length)
{
if(!valid_iv_length(length))
throw Invalid_IV_Length(name(), length);
m_state[12] = 0;
m_state[13] = 0;
if(length == 8)
{
m_state[14] = load_le<u32bit>(iv, 0);
m_state[15] = load_le<u32bit>(iv, 1);
}
else if(length == 12)
{
m_state[13] = load_le<u32bit>(iv, 0);
m_state[14] = load_le<u32bit>(iv, 1);
m_state[15] = load_le<u32bit>(iv, 2);
}
chacha(m_buffer.data(), m_state.data());
++m_state[12];
m_state[13] += (m_state[12] == 0);
m_position = 0;
}
/*
* Combine cipher stream with message
*/
void ChaCha::cipher(const byte in[], byte out[], size_t length)
{
while(length >= m_buffer.size() - m_position)
{
xor_buf(out, in, &m_buffer[m_position], m_buffer.size() - m_position);
length -= (m_buffer.size() - m_position);
in += (m_buffer.size() - m_position);
out += (m_buffer.size() - m_position);
chacha(m_buffer.data(), m_state.data());
++m_state[12];
m_state[13] += (m_state[12] == 0);
m_position = 0;
}
xor_buf(out, in, &m_buffer[m_position], length);
m_position += length;
}
bool tx_extra_message::encrypt(size_t index, const std::string &message, const AccountPublicAddress *recipient, const KeyPair &txkey) {
size_t mlen = message.size();
std::unique_ptr<char[]> buf(new char[mlen + TX_EXTRA_MESSAGE_CHECKSUM_SIZE]);
memcpy(buf.get(), message.data(), mlen);
memset(buf.get() + mlen, 0, TX_EXTRA_MESSAGE_CHECKSUM_SIZE);
mlen += TX_EXTRA_MESSAGE_CHECKSUM_SIZE;
if (recipient) {
message_key_data key_data;
if (!generate_key_derivation(recipient->spendPublicKey, txkey.secretKey, key_data.derivation)) {
return false;
}
key_data.magic1 = 0x80;
key_data.magic2 = 0;
Hash h = cn_fast_hash(&key_data, sizeof(message_key_data));
uint64_t nonce = SWAP64LE(index);
chacha(10, buf.get(), mlen, reinterpret_cast<uint8_t *>(&h), reinterpret_cast<uint8_t *>(&nonce), buf.get());
}
data.assign(buf.get(), mlen);
return true;
}
