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Generate hashes with random keys to avoid collisions #212

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Generate hashes with random keys to avoid collisions #212

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19 changes: 7 additions & 12 deletions src/util/common/hashmap.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -9,27 +9,22 @@
#include "buffer.hpp"
#include "crypto/siphash.h"
#include "hash.hpp"
#include "random_source.hpp"

#include <array>
#include <cstring>

namespace cbdc::hashing {
/// \brief SipHash function to generate STL data structure hash keys for
/// system IDs.
///
/// [TODO: Uses randomly generated initialization keys to insure that
/// colliding values will differ from run to run.] For transaction data
/// that comes from users, it is important to key data in sets and hashmaps
/// non-deterministically. Otherwise, malicious actors might pre-calculate
/// colliding values and spam the system with them to cripple performance.
/// \tparam T hash-like type to hash.
template<class T>
struct const_sip_hash {
static_assert(std::is_trivial_v<T>);
auto operator()(T const& tx) const noexcept -> size_t {
// TODO: pick the initialization key at random.
static constexpr std::array<uint64_t, 2> siphash_key{0x1337,
0x1337};
auto generator = random_source("/dev/urandom");
std::array<uint64_t, 2> siphash_key{generator(),
generator()};
CSipHasher hasher(siphash_key[0], siphash_key[1]);
std::array<unsigned char, sizeof(tx)> tx_arr{};
std::memcpy(tx_arr.data(), &tx, sizeof(tx));
Expand All @@ -41,9 +36,9 @@ namespace cbdc::hashing {
template<>
struct const_sip_hash<buffer> {
auto operator()(const buffer& buf) const noexcept -> size_t {
// TODO: pick the initialization key at random.
static constexpr std::array<uint64_t, 2> siphash_key{0x1337,
0x1337};
auto generator = random_source("/dev/urandom");
std::array<uint64_t, 2> siphash_key{generator(),
generator()};
CSipHasher hasher(siphash_key[0], siphash_key[1]);
std::vector<unsigned char> arr(buf.size());
std::memcpy(arr.data(), buf.data(), buf.size());
Expand Down