added LWMA

src/cryptonote_basic/difficulty.cpp

@@ -33,6 +33,7 @@
 #include <cstddef>
 #include <cstdint>
 #include <vector>
+#include <boost/math/special_functions/round.hpp>
 
 #include "common/int-util.h"
 #include "crypto/hash.h"
@@ -162,4 +163,81 @@ namespace cryptonote {
     return (low + time_span - 1) / time_span;
   }
 
+// LWMA difficulty algorithm
+// Background:  https://github.com/zawy12/difficulty-algorithms/issues/3
+// Copyright (c) 2017-2018 Zawy (pseudocode)
+// MIT license http://www.opensource.org/licenses/mit-license.php
+// Copyright (c) 2018 Wownero Inc., a Monero Enterprise Alliance partner company
+// Copyright (c) 2018 The Karbowanec developers (initial code)
+// Copyright (c) 2018 Haven Protocol (refinements)
+// Degnr8, Karbowanec, Masari, Bitcoin Gold, Bitcoin Candy, and Haven have contributed.
+
+// This algorithm is: next_difficulty = harmonic_mean(Difficulties) * T / LWMA(Solvetimes)
+// The harmonic_mean(Difficulties) = 1/average(Targets) so it is also:
+// next_target = avg(Targets) * LWMA(Solvetimes) / T.
+// This is "the best algorithm" because it has lowest root-mean-square error between 
+// needed & actual difficulty during hash attacks while having the lowest standard 
+// deviation during stable hashrate. That is, it's the fastest for a given stability and vice versa.
+// Do not use "if solvetime < 1 then solvetime = 1" which allows a catastrophic exploit.
+// Do not sort timestamps.  "Solvetimes" and "LWMA" variables must allow negatives.
+// Do not use MTP as most recent block.  Do not use (POW)Limits, filtering, or tempering.
+// Do not forget to set N (aka DIFFICULTY_WINDOW in Cryptonote) to recommendation below.
+// The nodes' future time limit (FTL) aka CRYPTONOTE_BLOCK_FUTURE_TIME_LIMIT needs to
+// be reduced from 60*60*2 to 500 seconds to prevent timestamp manipulation from miner's with 
+//  > 50% hash power.  If this is too small, it can be increased to 1000 at a cost in protection.
+  
+// Cryptonote clones:  #define DIFFICULTY_BLOCKS_COUNT_V2 DIFFICULTY_WINDOW_V2 + 1
+
+
+  difficulty_type next_difficulty_v2(std::vector<std::uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties, size_t target_seconds) {
+
+    const int64_t T = static_cast<int64_t>(target_seconds);
+    
+    size_t N = DIFFICULTY_WINDOW_V2;
+
+    // Return a difficulty of 1 for first 3 blocks if it's the start of the chain.
+    if (timestamps.size() < 4) { 
+      return 1; 
+    }
+    // Otherwise, use a smaller N if the start of the chain is less than N+1.
+    else if ( timestamps.size() < N+1 ) { 
+      N = timestamps.size() - 1;
+    }
+    // Otherwise make sure timestamps and cumulative_difficulties are correct size.
+    else {  
+      timestamps.resize(N+1);  
+      cumulative_difficulties.resize(N+1);
+    }
+    // To get an average solvetime to within +/- ~0.1%, use an adjustment factor.
+    // adjust=0.999 for 80 < N < 120(?)
+    const double adjust = 0.998;
+    // The divisor k normalizes the LWMA sum to a standard LWMA.
+    const double k = N * (N + 1) / 2;
+
+    double LWMA(0), sum_inverse_D(0), harmonic_mean_D(0), nextDifficulty(0);
+    int64_t solveTime(0);
+    uint64_t difficulty(0), next_difficulty(0);
+
+    // Loop through N most recent blocks. N is most recently solved block.
+    for (size_t i = 1; i <= N; i++) {
+      solveTime = static_cast<int64_t>(timestamps[i]) - static_cast<int64_t>(timestamps[i - 1]);
+      solveTime = std::min<int64_t>((T * 7), std::max<int64_t>(solveTime, (-7 * T)));
+      difficulty = cumulative_difficulties[i] - cumulative_difficulties[i - 1];
+      LWMA += solveTime * i / k;
+      sum_inverse_D += 1 / static_cast<double>(difficulty);
+    }
+
+    harmonic_mean_D = N / sum_inverse_D;
+
+    // Keep LWMA sane in case something unforeseen occurs.
+    if (static_cast<int64_t>(boost::math::round(LWMA)) < T / 20)
+      LWMA = static_cast<double>(T / 20);
+
+    nextDifficulty = harmonic_mean_D * T / LWMA * adjust;
+
+    // No limits should be employed, but this is correct way to employ a 20% symmetrical limit:
+    // nextDifficulty=max(previous_Difficulty*0.8,min(previous_Difficulty/0.8, next_Difficulty));
+    next_difficulty = static_cast<uint64_t>(nextDifficulty);
+    return next_difficulty;
+  }
 }

src/cryptonote_basic/difficulty.h

@@ -53,4 +53,5 @@ namespace cryptonote
      */
     bool check_hash(const crypto::hash &hash, difficulty_type difficulty);
     difficulty_type next_difficulty(std::vector<std::uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties, size_t target_seconds);
+    difficulty_type next_difficulty_v2(std::vector<std::uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties, size_t target_seconds);
 }

src/cryptonote_config.h

@@ -44,6 +44,7 @@
 #define CURRENT_TRANSACTION_VERSION                     2
 #define CURRENT_BLOCK_MAJOR_VERSION                     7
 #define CURRENT_BLOCK_MINOR_VERSION                     7
+#define CRYPTONOTE_BLOCK_FUTURE_TIME_LIMIT_V2           300*2
 #define CRYPTONOTE_BLOCK_FUTURE_TIME_LIMIT              60*60*2
 #define CRYPTONOTE_DEFAULT_TX_SPENDABLE_AGE             10
 
@@ -74,9 +75,11 @@
 
 #define DIFFICULTY_TARGET_V2                            300
 #define DIFFICULTY_TARGET_V1                            300
+#define DIFFICULTY_WINDOW_V2                            60
 #define DIFFICULTY_WINDOW                               720 // blocks
 #define DIFFICULTY_LAG                                  15  // !!!
 #define DIFFICULTY_CUT                                  60  // timestamps to cut after sorting
+#define DIFFICULTY_BLOCKS_COUNT_V2                      DIFFICULTY_WINDOW_V2 + 1 // added +1 to make N=N
 #define DIFFICULTY_BLOCKS_COUNT                         DIFFICULTY_WINDOW + DIFFICULTY_LAG
 
 

src/cryptonote_core/blockchain.cpp

@@ -102,7 +102,8 @@ static const struct {
   time_t time;
 } testnet_hard_forks[] = {
 //{ 1, 1, 0, 1341378000 },
- { 7, 1, 0, 1519605000 }
+ { 7, 1, 0, 1519605000 },
+ { 8, 10, 0, 1523255371 }, 
 };
 
 static const uint64_t testnet_hard_fork_version_1_till = ((uint64_t)(1));
@@ -780,20 +781,29 @@ difficulty_type Blockchain::get_difficulty_for_next_block()
   std::vector<uint64_t> timestamps;
   std::vector<difficulty_type> difficulties;
   auto height = m_db->height();
+
+  uint8_t version = get_current_hard_fork_version();
+  size_t difficulty_blocks_count;
+  if (version == 7) {
+    difficulty_blocks_count = DIFFICULTY_BLOCKS_COUNT;
+  } else {
+    difficulty_blocks_count = DIFFICULTY_BLOCKS_COUNT_V2;
+  }
+
   // ND: Speedup
   // 1. Keep a list of the last 735 (or less) blocks that is used to compute difficulty,
   //    then when the next block difficulty is queried, push the latest height data and
   //    pop the oldest one from the list. This only requires 1x read per height instead
   //    of doing 735 (DIFFICULTY_BLOCKS_COUNT).
-  if (m_timestamps_and_difficulties_height != 0 && ((height - m_timestamps_and_difficulties_height) == 1))
+  if (m_timestamps_and_difficulties_height != 0 && ((height - m_timestamps_and_difficulties_height) == 1) && m_timestamps.size() >= difficulty_blocks_count)
   {
     uint64_t index = height - 1;
     m_timestamps.push_back(m_db->get_block_timestamp(index));
     m_difficulties.push_back(m_db->get_block_cumulative_difficulty(index));
 
-    while (m_timestamps.size() > DIFFICULTY_BLOCKS_COUNT)
+    while (m_timestamps.size() > difficulty_blocks_count)
       m_timestamps.erase(m_timestamps.begin());
-    while (m_difficulties.size() > DIFFICULTY_BLOCKS_COUNT)
+    while (m_difficulties.size() > difficulty_blocks_count)
       m_difficulties.erase(m_difficulties.begin());
 
     m_timestamps_and_difficulties_height = height;
@@ -802,7 +812,7 @@ difficulty_type Blockchain::get_difficulty_for_next_block()
   }
   else
   {
-    size_t offset = height - std::min < size_t > (height, static_cast<size_t>(DIFFICULTY_BLOCKS_COUNT));
+    size_t offset = height - std::min < size_t > (height, static_cast<size_t>(difficulty_blocks_count));
     if (offset == 0)
       ++offset;
 
@@ -818,8 +828,12 @@ difficulty_type Blockchain::get_difficulty_for_next_block()
     m_timestamps = timestamps;
     m_difficulties = difficulties;
   }
-  size_t target = get_difficulty_target();
+  size_t target = DIFFICULTY_TARGET_V2;
+  if (version == 7) {
     return next_difficulty(timestamps, difficulties, target);
+  } else {
+    return next_difficulty_v2(timestamps, difficulties, target);
+  }
 }
 //------------------------------------------------------------------
 // This function removes blocks from the blockchain until it gets to the
@@ -967,16 +981,23 @@ difficulty_type Blockchain::get_next_difficulty_for_alternative_chain(const std:
   LOG_PRINT_L3("Blockchain::" << __func__);
   std::vector<uint64_t> timestamps;
   std::vector<difficulty_type> cumulative_difficulties;
+  uint8_t version = get_current_hard_fork_version();
+  size_t difficulty_blocks_count;
+  if (version == 7) {
+    difficulty_blocks_count = DIFFICULTY_BLOCKS_COUNT;
+  } else {
+    difficulty_blocks_count = DIFFICULTY_BLOCKS_COUNT_V2;
+  }
 
   // if the alt chain isn't long enough to calculate the difficulty target
   // based on its blocks alone, need to get more blocks from the main chain
-  if(alt_chain.size()< DIFFICULTY_BLOCKS_COUNT)
+  if(alt_chain.size()< difficulty_blocks_count)
   {
     CRITICAL_REGION_LOCAL(m_blockchain_lock);
 
     // Figure out start and stop offsets for main chain blocks
     size_t main_chain_stop_offset = alt_chain.size() ? alt_chain.front()->second.height : bei.height;
-    size_t main_chain_count = DIFFICULTY_BLOCKS_COUNT - std::min(static_cast<size_t>(DIFFICULTY_BLOCKS_COUNT), alt_chain.size());
+    size_t main_chain_count = difficulty_blocks_count - std::min(static_cast<size_t>(difficulty_blocks_count), alt_chain.size());
     main_chain_count = std::min(main_chain_count, main_chain_stop_offset);
     size_t main_chain_start_offset = main_chain_stop_offset - main_chain_count;
 
@@ -991,7 +1012,7 @@ difficulty_type Blockchain::get_next_difficulty_for_alternative_chain(const std:
     }
 
     // make sure we haven't accidentally grabbed too many blocks...maybe don't need this check?
-    CHECK_AND_ASSERT_MES((alt_chain.size() + timestamps.size()) <= DIFFICULTY_BLOCKS_COUNT, false, "Internal error, alt_chain.size()[" << alt_chain.size() << "] + vtimestampsec.size()[" << timestamps.size() << "] NOT <= DIFFICULTY_WINDOW[]" << DIFFICULTY_BLOCKS_COUNT);
+    CHECK_AND_ASSERT_MES((alt_chain.size() + timestamps.size()) <= difficulty_blocks_count, false, "Internal error, alt_chain.size()[" << alt_chain.size() << "] + vtimestampsec.size()[" << timestamps.size() << "] NOT <= DIFFICULTY_WINDOW[]" << DIFFICULTY_BLOCKS_COUNT);
 
     for (auto it : alt_chain)
     {
@@ -1003,8 +1024,8 @@ difficulty_type Blockchain::get_next_difficulty_for_alternative_chain(const std:
   // and timestamps from it alone
   else
   {
-    timestamps.resize(static_cast<size_t>(DIFFICULTY_BLOCKS_COUNT));
-    cumulative_difficulties.resize(static_cast<size_t>(DIFFICULTY_BLOCKS_COUNT));
+    timestamps.resize(static_cast<size_t>(difficulty_blocks_count));
+    cumulative_difficulties.resize(static_cast<size_t>(difficulty_blocks_count));
     size_t count = 0;
     size_t max_i = timestamps.size()-1;
     // get difficulties and timestamps from most recent blocks in alt chain
@@ -1013,7 +1034,7 @@ difficulty_type Blockchain::get_next_difficulty_for_alternative_chain(const std:
       timestamps[max_i - count] = it->second.bl.timestamp;
       cumulative_difficulties[max_i - count] = it->second.cumulative_difficulty;
       count++;
-      if(count >= DIFFICULTY_BLOCKS_COUNT)
+      if(count >= difficulty_blocks_count)
         break;
     }
   }
@@ -1022,8 +1043,13 @@ difficulty_type Blockchain::get_next_difficulty_for_alternative_chain(const std:
   size_t target = get_ideal_hard_fork_version(bei.height) < 2 ? DIFFICULTY_TARGET_V1 : DIFFICULTY_TARGET_V2;
 
   // calculate the difficulty target for the block and return it
+  if (version == 7) {
     return next_difficulty(timestamps, cumulative_difficulties, target);
+  } else {
+    return next_difficulty_v2(timestamps, cumulative_difficulties, target);
   }
+}
+
 //------------------------------------------------------------------
 // This function does a sanity check on basic things that all miner
 // transactions have in common, such as:
@@ -3174,7 +3200,8 @@ bool Blockchain::check_block_timestamp(std::vector<uint64_t>& timestamps, const
 bool Blockchain::check_block_timestamp(const block& b, uint64_t& median_ts) const
 {
   LOG_PRINT_L3("Blockchain::" << __func__);
-  if(b.timestamp > get_adjusted_time() + CRYPTONOTE_BLOCK_FUTURE_TIME_LIMIT)
+  uint64_t cryptonote_block_future_time_limit = get_current_hard_fork_version() < 7 ? CRYPTONOTE_BLOCK_FUTURE_TIME_LIMIT : CRYPTONOTE_BLOCK_FUTURE_TIME_LIMIT_V2;
+  if(b.timestamp > get_adjusted_time() + cryptonote_block_future_time_limit)
   {
     MERROR_VER("Timestamp of block with id: " << get_block_hash(b) << ", " << b.timestamp << ", bigger than adjusted time + 2 hours");
     return false;

src/p2p/net_node.inl

@@ -370,6 +370,8 @@ namespace nodetool
   {
     std::set<std::string> full_addrs;
     if (nettype == cryptonote::TESTNET) {
+             full_addrs.insert("167.160.87.144:11180");
+             full_addrs.insert("5.255.86.129:11180");
     } else {
              full_addrs.insert("66.70.218.230:34567");
              full_addrs.insert("34.209.48.213:34567");