Merge pull request #1201 from rnicoll/1.10-sync

Consensus fixes

1 files changed, 16 insertions, 2 deletions

diff --git a/src/pow.cpp b/src/pow.cpp
index 44eee9c35..1dac0b81c 100644
--- a/src/pow.cpp
+++ b/src/pow.cpp
@@ -20,6 +20,15 @@ unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHead
     if (pindexLast == NULL)
         return nProofOfWorkLimit;
 
+    // Dogecoin: Special rules for minimum difficulty blocks with Digishield
+    if (AllowDigishieldMinDifficultyForBlock(pindexLast, pblock, params))
+    {
+        // Special difficulty rule for testnet:
+        // If the new block's timestamp is more than 2* nTargetSpacing minutes
+        // then allow mining of a min-difficulty block.
+        return nProofOfWorkLimit;
+    }
+
     // Only change once per difficulty adjustment interval
     if ((pindexLast->nHeight+1) % params.DifficultyAdjustmentInterval() != 0)
     {
@@ -42,8 +51,14 @@ unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHead
         return pindexLast->nBits;
     }
 
+    // Litecoin: This fixes an issue where a 51% attack can change difficulty at will.
+    // Go back the full period unless it's the first retarget after genesis. Code courtesy of Art Forz
+    int blockstogoback = params.DifficultyAdjustmentInterval()-1;
+    if ((pindexLast->nHeight+1) != params.DifficultyAdjustmentInterval())
+        blockstogoback = params.DifficultyAdjustmentInterval();
+
     // Go back by what we want to be 14 days worth of blocks
-    int nHeightFirst = pindexLast->nHeight - (params.DifficultyAdjustmentInterval()-1);
+    int nHeightFirst = pindexLast->nHeight - blockstogoback;
     assert(nHeightFirst >= 0);
     const CBlockIndex* pindexFirst = pindexLast->GetAncestor(nHeightFirst);
     assert(pindexFirst);
@@ -55,7 +70,6 @@ unsigned int CalculateNextWorkRequired(const CBlockIndex* pindexLast, int64_t nF
 {
     // Limit adjustment step
     int64_t nActualTimespan = pindexLast->GetBlockTime() - nFirstBlockTime;
-    LogPrintf("  nActualTimespan = %d  before bounds\n", nActualTimespan);
     if (nActualTimespan < params.nPowTargetTimespan/4)
         nActualTimespan = params.nPowTargetTimespan/4;
     if (nActualTimespan > params.nPowTargetTimespan*4)