PPCoin: Modify coinstake target protocol

        Avoid multiple nodes generating coinstake at the same moment

diff --git a/src/main.cpp b/src/main.cpp
index 08ceb20..0866ab0 100644 (file)
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1284,17 +1284,23 @@ bool CBlock::SetBestChain(CTxDB& txdb, CBlockIndex* pindexNew)
 
 // ppcoin: coinstake must meet hash target according to the protocol:
 // at least one input must meet the formula
-//     hash(nBits + txPrev.block.nTime + txPrev.nTime + nTime) < bnTarget * nCoinDay
+//     hash(nBits + txPrev.block.nTime + txPrev.offset + txPrev.nTime + txPrev.vout.n + nTime) < bnTarget * nCoinDay
 // this ensures that the chance of getting a coinstake is proportional to the
 // amount of coin age one owns.
 // The reason this hash is chosen is the following:
-//   nBits: encodes all past block timestamps, prevents computing hash in advance
-//   txPrev.block.nTime: prevent nodes from guessing a good timestamp to generate
-//       transaction for future advantage
-//   txPrev.nTime: prevent nodes from meeting target simultaneously
-//   block/tx hash should not be used here as they can be generated in vast quatities
-//       so as to generate blocks faster, degrading the system back into a proof-of-work
-//       situation.
+//   nBits: encodes all past block timestamps, making computing hash in advance
+//          more difficult
+//   txPrev.block.nTime: prevent nodes from guessing a good timestamp to
+//                       generate transaction for future advantage
+//   txPrev.offset: offset of txPrev inside block, to reduce the chance of 
+//                  nodes generating coinstake at the same time
+//   txPrev.nTime: reduce the chance of nodes generating coinstake at the same
+//                 time
+//   txPrev.vout.n: output number of txPrev, to reduce the chance of nodes
+//                  generating coinstake at the same time
+//   block/tx hash should not be used here as they can be generated in vast
+//   quantities so as to generate blocks faster, degrading the system back into
+//   a proof-of-work situation.
 //
 bool CTransaction::CheckProofOfStake(CTxDB& txdb, unsigned int nBits) const
 {
@@ -1325,7 +1331,7 @@ bool CTransaction::CheckProofOfStake(CTxDB& txdb, unsigned int nBits) const
         CBigNum bnCoinDay = CBigNum(nValueIn) * (nTime-txPrev.nTime) / COIN / (24 * 60 * 60);
         // Calculate hash
         CDataStream ss(SER_GETHASH, VERSION);
-        ss << nBits << block.nTime << txPrev.nTime << nTime;
+        ss << nBits << block.nTime << (txindex.pos.nTxPos - txindex.pos.nBlockPos) << txPrev.nTime << txin.prevout.n << nTime;
         if (CBigNum(Hash(ss.begin(), ss.end())) <= bnCoinDay * bnTargetPerCoinDay)
             return true;
     }

diff --git a/src/wallet.cpp b/src/wallet.cpp
index f993ab7..f44fb22 100644 (file)
--- a/src/wallet.cpp
+++ b/src/wallet.cpp
@@ -1106,7 +1106,7 @@ bool CWallet::CreateCoinStake(CScript scriptPubKey, unsigned int nBits, CTransac
             CBigNum bnCoinDay = CBigNum(nValueIn) * (txNew.nTime-pcoin.first->nTime) / COIN / (24 * 60 * 60);
             // Calculate hash
             CDataStream ss(SER_GETHASH, VERSION);
-            ss << nBits << block.nTime << pcoin.first->nTime << txNew.nTime;
+            ss << nBits << block.nTime << (txindex.pos.nTxPos - txindex.pos.nBlockPos) << pcoin.first->nTime << pcoin.second << txNew.nTime;
             if (CBigNum(Hash(ss.begin(), ss.end())) <= bnCoinDay * bnTargetPerCoinDay)
             {
                 txNew.vin.push_back(CTxIn(pcoin.first->GetHash(), pcoin.second));