Fix spending for v1 zPIV created before block 1050020.

The transition to v2 zPIV and reset of the accumulators caused blocks 1050000 - 1050010 to be accumulated twice. This was causing many v1 zPIV to not create valid witnesses. This problem is fixed by double accumulating blocks 1050000-1050010 when creating the witness.

src/accumulators.cpp

@@ -402,7 +402,7 @@ bool GetAccumulatorValue(int& nHeight, const libzerocoin::CoinDenomination denom
         //Start at the first zerocoin
         libzerocoin::Accumulator accumulator(Params().Zerocoin_Params(false), denom);
         bnAccValue = accumulator.getValue();
-        nHeight = Params().Zerocoin_Block_V2_Start() + 10;
+        nHeight = Params().Zerocoin_StartHeight() + 10;
         return true;
     }
 
@@ -437,6 +437,10 @@ bool GenerateAccumulatorWitness(const PublicCoin &coin, Accumulator& accumulator
     if (!GetTransaction(txid, txMinted, hashBlock))
         return error("%s failed to read tx", __func__);
 
+    int nHeightTest;
+    if (!IsTransactionInChain(txid, nHeightTest))
+        return error("%s: mint tx %s is not in chain", __func__, txid.GetHex());
+
     int nHeightMintAdded = mapBlockIndex[hashBlock]->nHeight;
 
     //get the checkpoint added at the next multiple of 10
@@ -467,6 +471,8 @@ bool GenerateAccumulatorWitness(const PublicCoin &coin, Accumulator& accumulator
     nMintsAdded = 0;
     RandomizeSecurityLevel(nSecurityLevel); //make security level not always the same and predictable
     libzerocoin::Accumulator witnessAccumulator = accumulator;
+
+    bool fDoubleCounted = false;
     while (pindex) {
         if (pindex->nHeight != nAccStartHeight && pindex->pprev->nAccumulatorCheckpoint != pindex->nAccumulatorCheckpoint)
             ++nCheckpointsAdded;
@@ -488,8 +494,17 @@ bool GenerateAccumulatorWitness(const PublicCoin &coin, Accumulator& accumulator
         }
 
         nMintsAdded += AddBlockMintsToAccumulator(coin, nHeightMintAdded, pindex, &witnessAccumulator, true);
+
+        // 10 blocks were accumulated twice when zPIV v2 was activated
+        if (pindex->nHeight == 1050010 && !fDoubleCounted) {
+            pindex = chainActive[1050000];
+            fDoubleCounted = true;
+            continue;
+        }
+
         pindex = chainActive.Next(pindex);
     }
+
     witness.resetValue(witnessAccumulator, coin);
     if (!witness.VerifyWitness(accumulator, coin))
         return error("%s: failed to verify witness", __func__);