Fix zeitgeist2 attack thanks to Lolcust and ArtForz.

coblee · Oct 10, 2011 · b1be772 · b1be772
1 parent 1a4faf7
commit b1be772
Showing 1 changed file with 7 additions and 1 deletion.
diff --git a/src/main.cpp b/src/main.cpp
@@ -661,9 +661,15 @@ unsigned int static GetNextWorkRequired(const CBlockIndex* pindexLast)
     if ((pindexLast->nHeight+1) % nInterval != 0)
         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 = nInterval-1;
+    if ((pindexLast->nHeight+1) != nInterval)
+        blockstogoback = nInterval;
+
     // Go back by what we want to be 14 days worth of blocks
     const CBlockIndex* pindexFirst = pindexLast;
-    for (int i = 0; pindexFirst && i < nInterval-1; i++)
+    for (int i = 0; pindexFirst && i < blockstogoback; i++)
         pindexFirst = pindexFirst->pprev;
     assert(pindexFirst);