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wallet2: use a gamma distribution to pick fake outs 

as per "An Empirical Analysis of Linkability in the Monero
Blockchain", by Miller et al.
This commit is contained in:
moneromooo-monero 2018-03-23 15:43:38 +00:00
parent a9b83f5a6e
commit 34d4b798d4
No known key found for this signature in database
GPG Key ID: 686F07454D6CEFC3
2 changed files with 115 additions and 30 deletions
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97
src/wallet/wallet2.cpp
View File

@ -2502,7 +2502,7 @@ bool wallet2::refresh(bool trusted_daemon, uint64_t & blocks_fetched, bool& rece
return ok;
}
//----------------------------------------------------------------------------------------------------
bool wallet2::get_output_distribution(uint64_t &start_height, std::vector<uint64_t> &distribution)
bool wallet2::get_rct_distribution(uint64_t &start_height, std::vector<uint64_t> &distribution)
{
uint32_t rpc_version;
boost::optional<std::string> result = m_node_rpc_proxy.get_rpc_version(rpc_version);
@ -6129,22 +6129,42 @@ void wallet2::get_outs(std::vector<std::vector<tools::wallet2::get_outs_entry>>
bool is_shortly_after_segregation_fork = height >= segregation_fork_height && height < segregation_fork_height + SEGREGATION_FORK_VICINITY;
bool is_after_segregation_fork = height >= segregation_fork_height;
// if we have at least one rct out, get the distribution, or fall back to the previous system
uint64_t rct_start_height;
std::vector<uint64_t> rct_offsets;
bool has_rct = false;
for (size_t idx: selected_transfers)
if (m_transfers[idx].is_rct())
{ has_rct = true; break; }
const bool has_rct_distribution = has_rct && get_rct_distribution(rct_start_height, rct_offsets);
if (has_rct_distribution)
{
// check we're clear enough of rct start, to avoid corner cases below
THROW_WALLET_EXCEPTION_IF(rct_offsets.size() <= CRYPTONOTE_DEFAULT_TX_SPENDABLE_AGE,
error::get_output_distribution, "Not enough rct outputs");
}
// get histogram for the amounts we need
cryptonote::COMMAND_RPC_GET_OUTPUT_HISTOGRAM::request req_t = AUTO_VAL_INIT(req_t);
cryptonote::COMMAND_RPC_GET_OUTPUT_HISTOGRAM::response resp_t = AUTO_VAL_INIT(resp_t);
m_daemon_rpc_mutex.lock();
// request histogram for all outputs, except 0 if we have the rct distribution
for(size_t idx: selected_transfers)
if (!m_transfers[idx].is_rct() || !has_rct_distribution)
req_t.amounts.push_back(m_transfers[idx].is_rct() ? 0 : m_transfers[idx].amount());
if (!req_t.amounts.empty())
{
std::sort(req_t.amounts.begin(), req_t.amounts.end());
auto end = std::unique(req_t.amounts.begin(), req_t.amounts.end());
req_t.amounts.resize(std::distance(req_t.amounts.begin(), end));
req_t.unlocked = true;
req_t.recent_cutoff = time(NULL) - RECENT_OUTPUT_ZONE;
m_daemon_rpc_mutex.lock();
bool r = net_utils::invoke_http_json_rpc("/json_rpc", "get_output_histogram", req_t, resp_t, m_http_client, rpc_timeout);
m_daemon_rpc_mutex.unlock();
THROW_WALLET_EXCEPTION_IF(!r, error::no_connection_to_daemon, "transfer_selected");
THROW_WALLET_EXCEPTION_IF(resp_t.status == CORE_RPC_STATUS_BUSY, error::daemon_busy, "get_output_histogram");
THROW_WALLET_EXCEPTION_IF(resp_t.status != CORE_RPC_STATUS_OK, error::get_histogram_error, resp_t.status);
}
// if we want to segregate fake outs pre or post fork, get distribution
std::unordered_map<uint64_t, std::pair<uint64_t, uint64_t>> segregation_limit;
@ -6200,6 +6220,36 @@ void wallet2::get_outs(std::vector<std::vector<tools::wallet2::get_outs_entry>>
COMMAND_RPC_GET_OUTPUTS_BIN::request req = AUTO_VAL_INIT(req);
COMMAND_RPC_GET_OUTPUTS_BIN::response daemon_resp = AUTO_VAL_INIT(daemon_resp);
struct gamma_engine
{
typedef uint64_t result_type;
static constexpr result_type min() { return 0; }
static constexpr result_type max() { return std::numeric_limits<result_type>::max(); }
result_type operator()() { return crypto::rand<result_type>(); }
} engine;
static const double shape = 19.28/*16.94*/;
//static const double shape = m_testnet ? 17.02 : 17.28;
static const double scale = 1/1.61;
std::gamma_distribution<double> gamma(shape, scale);
auto pick_gamma = [&]()
{
double x = gamma(engine);
x = exp(x);
uint64_t block_offset = x / DIFFICULTY_TARGET_V2; // this assumes constant target over the whole rct range
if (block_offset >= rct_offsets.size() - 1)
return std::numeric_limits<uint64_t>::max(); // bad pick
block_offset = rct_offsets.size() - 2 - block_offset;
THROW_WALLET_EXCEPTION_IF(block_offset >= rct_offsets.size() - 1, error::wallet_internal_error, "Bad offset calculation");
THROW_WALLET_EXCEPTION_IF(rct_offsets[block_offset + 1] < rct_offsets[block_offset],
error::get_output_distribution, "Decreasing offsets in rct distribution: " +
std::to_string(block_offset) + ": " + std::to_string(rct_offsets[block_offset]) + ", " +
std::to_string(block_offset + 1) + ": " + std::to_string(rct_offsets[block_offset + 1]));
uint64_t n_rct = rct_offsets[block_offset + 1] - rct_offsets[block_offset];
if (n_rct == 0)
return rct_offsets[block_offset] ? rct_offsets[block_offset] - 1 : 0;
return rct_offsets[block_offset] + crypto::rand<uint64_t>() % n_rct;
};
size_t num_selected_transfers = 0;
for(size_t idx: selected_transfers)
{
@ -6210,6 +6260,7 @@ void wallet2::get_outs(std::vector<std::vector<tools::wallet2::get_outs_entry>>
// request more for rct in base recent (locked) coinbases are picked, since they're locked for longer
size_t requested_outputs_count = base_requested_outputs_count + (td.is_rct() ? CRYPTONOTE_MINED_MONEY_UNLOCK_WINDOW - CRYPTONOTE_DEFAULT_TX_SPENDABLE_AGE : 0);
size_t start = req.outputs.size();
bool use_histogram = amount != 0 || !has_rct_distribution;
const bool output_is_pre_fork = td.m_block_height < segregation_fork_height;
uint64_t num_outs = 0, num_recent_outs = 0;
@ -6265,26 +6316,41 @@ void wallet2::get_outs(std::vector<std::vector<tools::wallet2::get_outs_entry>>
num_post_fork_outs = num_outs - segregation_limit[amount].first;
}
if (use_histogram)
{
LOG_PRINT_L1("" << num_outs << " unlocked outputs of size " << print_money(amount));
THROW_WALLET_EXCEPTION_IF(num_outs == 0, error::wallet_internal_error,
"histogram reports no unlocked outputs for " + boost::lexical_cast<std::string>(amount) + ", not even ours");
THROW_WALLET_EXCEPTION_IF(num_recent_outs > num_outs, error::wallet_internal_error,
"histogram reports more recent outs than outs for " + boost::lexical_cast<std::string>(amount));
}
else
{
// the base offset of the first rct output in the first unlocked block (or the one to be if there's none)
num_outs = rct_offsets[rct_offsets.size() - CRYPTONOTE_DEFAULT_TX_SPENDABLE_AGE];
LOG_PRINT_L1("" << num_outs << " unlocked rct outputs");
THROW_WALLET_EXCEPTION_IF(num_outs == 0, error::wallet_internal_error,
"histogram reports no unlocked rct outputs, not even ours");
}
// how many fake outs to draw on a pre-fork triangular distribution
// how many fake outs to draw on a pre-fork distribution
size_t pre_fork_outputs_count = requested_outputs_count * pre_fork_num_out_ratio;
size_t post_fork_outputs_count = requested_outputs_count * post_fork_num_out_ratio;
// how many fake outs to draw otherwise
size_t normal_output_count = requested_outputs_count - pre_fork_outputs_count - post_fork_outputs_count;
size_t recent_outputs_count = 0;
if (use_histogram)
{
// X% of those outs are to be taken from recent outputs
size_t recent_outputs_count = normal_output_count * RECENT_OUTPUT_RATIO;
recent_outputs_count = normal_output_count * RECENT_OUTPUT_RATIO;
if (recent_outputs_count == 0)
recent_outputs_count = 1; // ensure we have at least one, if possible
if (recent_outputs_count > num_recent_outs)
recent_outputs_count = num_recent_outs;
if (td.m_global_output_index >= num_outs - num_recent_outs && recent_outputs_count > 0)
--recent_outputs_count; // if the real out is recent, pick one less recent fake out
}
LOG_PRINT_L1("Fake output makeup: " << requested_outputs_count << " requested: " << recent_outputs_count << " recent, " <<
pre_fork_outputs_count << " pre-fork, " << post_fork_outputs_count << " post-fork, " <<
(requested_outputs_count - recent_outputs_count - pre_fork_outputs_count - post_fork_outputs_count) << " full-chain");
@ -6364,7 +6430,26 @@ void wallet2::get_outs(std::vector<std::vector<tools::wallet2::get_outs_entry>>
uint64_t i;
const char *type = "";
if (num_found - 1 < recent_outputs_count) // -1 to account for the real one we seeded with
if (amount == 0 && has_rct_distribution)
{
// gamma distribution
if (num_found -1 < recent_outputs_count + pre_fork_outputs_count)
{
do i = pick_gamma(); while (i >= segregation_limit[amount].first);
type = "pre-fork gamma";
}
else if (num_found -1 < recent_outputs_count + pre_fork_outputs_count + post_fork_outputs_count)
{
do i = pick_gamma(); while (i < segregation_limit[amount].first || i >= num_outs);
type = "post-fork gamma";
}
else
{
do i = pick_gamma(); while (i >= num_outs);
type = "gamma";
}
}
else if (num_found - 1 < recent_outputs_count) // -1 to account for the real one we seeded with
{
// triangular distribution over [a,b) with a=0, mode c=b=up_index_limit
uint64_t r = crypto::rand<uint64_t>() % ((uint64_t)1 << 53);
@ -6429,7 +6514,7 @@ void wallet2::get_outs(std::vector<std::vector<tools::wallet2::get_outs_entry>>
// get the keys for those
m_daemon_rpc_mutex.lock();
r = epee::net_utils::invoke_http_bin("/get_outs.bin", req, daemon_resp, m_http_client, rpc_timeout);
bool r = epee::net_utils::invoke_http_bin("/get_outs.bin", req, daemon_resp, m_http_client, rpc_timeout);
m_daemon_rpc_mutex.unlock();
THROW_WALLET_EXCEPTION_IF(!r, error::no_connection_to_daemon, "get_outs.bin");
THROW_WALLET_EXCEPTION_IF(daemon_resp.status == CORE_RPC_STATUS_BUSY, error::daemon_busy, "get_outs.bin");

2
src/wallet/wallet2.h
View File

@ -1209,7 +1209,7 @@ namespace tools
void cache_ringdb_key();
void clear_ringdb_key();
bool get_output_distribution(uint64_t &start_height, std::vector<uint64_t> &distribution);
bool get_rct_distribution(uint64_t &start_height, std::vector<uint64_t> &distribution);
uint64_t get_segregation_fork_height() const;