Peercoin: v0.5 protocol adjustment

Allow transaction output value to be 0.
Use dynamic stake modifier for kernel generation
Protocol switch schedule:
Testnet switch - Nov 16, 2015
Mainnet switch - Mar 15, 2016

src/db.cpp

@@ -529,6 +529,16 @@ bool CTxDB::WriteV04UpgradeTime(const unsigned int& nUpgradeTime)
     return Write(string("nProtocolV04UpgradeTime"), nUpgradeTime);
 }
 
+bool CTxDB::ReadV05UpgradeTime(unsigned int& nUpgradeTime)
+{
+    return Read(string("nProtocolV05UpgradeTime"), nUpgradeTime);
+}
+
+bool CTxDB::WriteV05UpgradeTime(const unsigned int& nUpgradeTime)
+{
+    return Write(string("nProtocolV05UpgradeTime"), nUpgradeTime);
+}
+
 CBlockIndex static * InsertBlockIndex(uint256 hash)
 {
     if (hash == 0)

src/db.h

@@ -302,6 +302,8 @@ class CTxDB : public CDB
     bool WriteCheckpointPubKey(const std::string& strPubKey);
     bool ReadV04UpgradeTime(unsigned int& nUpgradeTime);
     bool WriteV04UpgradeTime(const unsigned int& nUpgradeTime);
+    bool ReadV05UpgradeTime(unsigned int& nUpgradeTime);
+    bool WriteV05UpgradeTime(const unsigned int& nUpgradeTime);
     bool LoadBlockIndex();
 };
 

src/kernel.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2012-2013 The PPCoin developers
+// Copyright (c) 2012-2015 The Peercoin developers
 // Distributed under the MIT/X11 software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
@@ -15,13 +15,24 @@ unsigned int nProtocolV03TestSwitchTime = 1359781000;
 // Protocol switch time of v0.4 kernel protocol
 unsigned int nProtocolV04SwitchTime     = 1399300000;
 unsigned int nProtocolV04TestSwitchTime = 1395700000;
+// Protocol switch time of v0.5 kernel protocol
+unsigned int nProtocolV05SwitchTime     = 1458000000;
+unsigned int nProtocolV05TestSwitchTime = 1447700000;
+
 // TxDB upgrade time for v0.4 protocol
 // Note: v0.4 upgrade does not require block chain re-download. However,
 //       user must upgrade before the protocol switch deadline, otherwise
 //       re-download of blockchain is required. The timestamp of upgrade
 //       is recorded in transaction database to alert user of the requirement.
 unsigned int nProtocolV04UpgradeTime    = 0;
 
+// TxDB upgrade time for v0.5 protocol
+// Note: v0.5 upgrade does not require block chain re-download. However,
+//       user must upgrade before the protocol switch deadline, otherwise
+//       re-download of blockchain is required. The timestamp of upgrade
+//       is recorded in transaction database to alert user of the requirement.
+unsigned int nProtocolV05UpgradeTime    = 0;
+
 // Modifier interval: time to elapse before new modifier is computed
 // Set to 6-hour for production network and 20-minute for test network
 unsigned int nModifierInterval = MODIFIER_INTERVAL;
@@ -47,6 +58,12 @@ bool IsProtocolV04(unsigned int nTimeBlock)
     return (nTimeBlock >= (fTestNet? nProtocolV04TestSwitchTime : nProtocolV04SwitchTime));
 }
 
+// Whether the given transaction is subject to new v0.5 protocol
+bool IsProtocolV05(unsigned int nTimeTx)
+{
+    return (nTimeTx >= (fTestNet? nProtocolV05TestSwitchTime : nProtocolV05SwitchTime));
+}
+
 // Get the last stake modifier and its generation time from a given block
 static bool GetLastStakeModifier(const CBlockIndex* pindex, uint64& nStakeModifier, int64& nModifierTime)
 {
@@ -253,9 +270,48 @@ bool ComputeNextStakeModifier(const CBlockIndex* pindexCurrent, uint64& nStakeMo
     return true;
 }
 
-// The stake modifier used to hash for a stake kernel is chosen as the stake
+// V0.5: Stake modifier used to hash for a stake kernel is chosen as the stake
+// modifier that is (nStakeMinAge minus a selection interval) earlier than the
+// stake, thus at least a selection interval later than the coin generating the // kernel, as the generating coin is from at least nStakeMinAge ago.
+static bool GetKernelStakeModifierV05(unsigned int nTimeTx, uint64& nStakeModifier, int& nStakeModifierHeight, int64& nStakeModifierTime, bool fPrintProofOfStake)
+{
+    const CBlockIndex* pindex = pindexBest;
+    nStakeModifierHeight = pindex->nHeight;
+    nStakeModifierTime = pindex->GetBlockTime();
+    int64 nStakeModifierSelectionInterval = GetStakeModifierSelectionInterval();
+
+    if (nStakeModifierTime + nStakeMinAge - nStakeModifierSelectionInterval <= (int64) nTimeTx)
+    {
+        // Best block is still more than
+        // (nStakeMinAge minus a selection interval) older than kernel timestamp
+        if (fPrintProofOfStake)
+            return error("GetKernelStakeModifier() : best block %s at height %d too old for stake",
+                pindex->GetBlockHash().ToString().c_str(), pindex->nHeight);
+        else
+            return false;
+    }
+    // loop to find the stake modifier earlier by 
+    // (nStakeMinAge minus a selection interval)
+    while (nStakeModifierTime + nStakeMinAge - nStakeModifierSelectionInterval >(int64) nTimeTx)
+    {
+        if (!pindex->pprev)
+        {   // reached genesis block; should not happen
+            return error("GetKernelStakeModifier() : reached genesis block");
+        }
+        pindex = pindex->pprev;
+        if (pindex->GeneratedStakeModifier())
+        {
+            nStakeModifierHeight = pindex->nHeight;
+            nStakeModifierTime = pindex->GetBlockTime();
+        }
+    }
+    nStakeModifier = pindex->nStakeModifier;
+    return true;
+}
+
+// V0.3: Stake modifier used to hash for a stake kernel is chosen as the stake
 // modifier about a selection interval later than the coin generating the kernel
-static bool GetKernelStakeModifier(uint256 hashBlockFrom, uint64& nStakeModifier, int& nStakeModifierHeight, int64& nStakeModifierTime, bool fPrintProofOfStake)
+static bool GetKernelStakeModifierV03(uint256 hashBlockFrom, uint64& nStakeModifier, int& nStakeModifierHeight, int64& nStakeModifierTime, bool fPrintProofOfStake)
 {
     nStakeModifier = 0;
     if (!mapBlockIndex.count(hashBlockFrom))
@@ -287,6 +343,15 @@ static bool GetKernelStakeModifier(uint256 hashBlockFrom, uint64& nStakeModifier
     return true;
 }
 
+// Get the stake modifier specified by the protocol to hash for a stake kernel
+static bool GetKernelStakeModifier(uint256 hashBlockFrom, unsigned int nTimeTx, uint64& nStakeModifier, int& nStakeModifierHeight, int64& nStakeModifierTime, bool fPrintProofOfStake)
+{
+    if (IsProtocolV05(nTimeTx))
+        return GetKernelStakeModifierV05(nTimeTx, nStakeModifier, nStakeModifierHeight, nStakeModifierTime, fPrintProofOfStake);
+    else
+        return GetKernelStakeModifierV03(hashBlockFrom, nStakeModifier, nStakeModifierHeight, nStakeModifierTime, fPrintProofOfStake);
+}
+
 // ppcoin kernel protocol
 // coinstake must meet hash target according to the protocol:
 // kernel (input 0) must meet the formula
@@ -295,6 +360,9 @@ static bool GetKernelStakeModifier(uint256 hashBlockFrom, uint64& nStakeModifier
 // amount of coin age one owns.
 // The reason this hash is chosen is the following:
 //   nStakeModifier: 
+//       (v0.5) uses dynamic stake modifier around 21 days before the kernel,
+//              versus static stake modifier about 9 days after the staked
+//              coin (txPrev) used in v0.3
 //       (v0.3) scrambles computation to make it very difficult to precompute
 //              future proof-of-stake at the time of the coin's confirmation
 //       (v0.2) nBits (deprecated): encodes all past block timestamps
@@ -334,7 +402,7 @@ bool CheckStakeKernelHash(unsigned int nBits, const CBlock& blockFrom, unsigned
     int64 nStakeModifierTime = 0;
     if (IsProtocolV03(nTimeTx))  // v0.3 protocol
     {
-        if (!GetKernelStakeModifier(blockFrom.GetHash(), nStakeModifier, nStakeModifierHeight, nStakeModifierTime, fPrintProofOfStake))
+        if (!GetKernelStakeModifier(blockFrom.GetHash(), nTimeTx, nStakeModifier, nStakeModifierHeight, nStakeModifierTime, fPrintProofOfStake))
             return false;
         ss << nStakeModifier;
     }
@@ -354,7 +422,7 @@ bool CheckStakeKernelHash(unsigned int nBits, const CBlock& blockFrom, unsigned
                 mapBlockIndex[blockFrom.GetHash()]->nHeight,
                 DateTimeStrFormat(blockFrom.GetBlockTime()).c_str());
         printf("CheckStakeKernelHash() : check protocol=%s modifier=0x%016"PRI64x" nTimeBlockFrom=%u nTxPrevOffset=%u nTimeTxPrev=%u nPrevout=%u nTimeTx=%u hashProof=%s\n",
-            IsProtocolV03(nTimeTx)? "0.3" : "0.2",
+            IsProtocolV05(nTimeTx)? "0.5" : (IsProtocolV03(nTimeTx)? "0.3" : "0.2"),
             IsProtocolV03(nTimeTx)? nStakeModifier : (uint64) nBits,
             nTimeBlockFrom, nTxPrevOffset, txPrev.nTime, prevout.n, nTimeTx,
             hashProofOfStake.ToString().c_str());

src/kernel.h

@@ -1,4 +1,4 @@
-// Copyright (c) 2012-2013 The PPCoin developers
+// Copyright (c) 2012-2015 The Peercoin developers
 // Distributed under the MIT/X11 software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 #ifndef PPCOIN_KERNEL_H
@@ -19,11 +19,15 @@ extern unsigned int nProtocolV03SwitchTime;
 extern unsigned int nProtocolV03TestSwitchTime;
 // TxDB upgrade time for v0.4 protocol
 extern unsigned int nProtocolV04UpgradeTime;
+// TxDB Upgrade time for v0.5 protocol
+extern unsigned int nProtocolV05UpgradeTime;
 
 // Whether a given coinstake is subject to new v0.3 protocol
 bool IsProtocolV03(unsigned int nTimeCoinStake);
 // Whether a given block is subject to new v0.4 protocol
 bool IsProtocolV04(unsigned int nTimeBlock);
+// Whether a given transaction is subject to new v0.5 protocol
+bool IsProtocolV05(unsigned int nTimeTx);
 
 // Compute the hash modifier for proof-of-stake
 bool ComputeNextStakeModifier(const CBlockIndex* pindexCurrent, uint64& nStakeModifier, bool& fGeneratedStakeModifier);

src/main.cpp

@@ -1,6 +1,6 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
 // Copyright (c) 2009-2012 The Bitcoin developers
-// Copyright (c) 2011-2013 The PPCoin developers
+// Copyright (c) 2011-2015 The Peercoin developers
 // Distributed under the MIT/X11 software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
@@ -481,7 +481,9 @@ bool CTransaction::CheckTransaction() const
         if (txout.IsEmpty() && (!IsCoinBase()) && (!IsCoinStake()))
             return DoS(100, error("CTransaction::CheckTransaction() : txout empty for user transaction"));
         // ppcoin: enforce minimum output amount
-        if ((!txout.IsEmpty()) && txout.nValue < MIN_TXOUT_AMOUNT)
+        // v0.5 protocol: zero amount allowed
+        if ((!txout.IsEmpty()) && txout.nValue < MIN_TXOUT_AMOUNT &&
+            !(IsProtocolV05(nTime) && (txout.nValue == 0)))
             return DoS(100, error("CTransaction::CheckTransaction() : txout.nValue below minimum"));
         if (txout.nValue > MAX_MONEY)
             return DoS(100, error("CTransaction::CheckTransaction() : txout.nValue too high"));
@@ -2372,7 +2374,9 @@ bool LoadBlockIndex(bool fAllowNew)
             CTxDB txdb;
             if (!txdb.WriteV04UpgradeTime(0))
                 return error("LoadBlockIndex() : failed to init upgrade info");
-            printf(" Upgrade Info: v0.4+ txdb initialization\n");
+            if (!txdb.WriteV05UpgradeTime(0))
+                return error("LoadBlockIndex() : failed to init upgrade info");
+            printf(" Upgrade Info: v0.5+ txdb initialization\n");
             txdb.Close();
         }
     }
@@ -2401,20 +2405,39 @@ bool LoadBlockIndex(bool fAllowNew)
         if (txdb.ReadV04UpgradeTime(nProtocolV04UpgradeTime))
         {
             if (nProtocolV04UpgradeTime)
-                printf(" Upgrade Info: txdb upgrade to v0.4 detected at timestamp %d\n", nProtocolV04UpgradeTime);
+                printf(" Upgrade Info: txdb upgrade v0.3->v0.4 detected at timestamp %d\n", nProtocolV04UpgradeTime);
             else
-                printf(" Upgrade Info: v0.4+ no txdb upgrade detected.\n");
+                printf(" Upgrade Info: no txdb upgrade v0.3->v0.4 detected.\n");
         }
         else
         {
             nProtocolV04UpgradeTime = GetTime();
-            printf(" Upgrade Info: upgrading txdb from v0.3 at timestamp %u\n", nProtocolV04UpgradeTime);
+            printf(" Upgrade Info: upgrading txdb from v0.3->v0.5 at timestamp %u\n", nProtocolV04UpgradeTime);
             if (!txdb.WriteV04UpgradeTime(nProtocolV04UpgradeTime))
                 return error("LoadBlockIndex() : failed to write upgrade info");
         }
         txdb.Close();
     }
 
+    {
+        CTxDB txdb;
+        if (txdb.ReadV05UpgradeTime(nProtocolV05UpgradeTime))
+        {
+            if (nProtocolV05UpgradeTime)
+                printf(" Upgrade Info: txdb upgrade to v0.5 detected at timestamp %d\n", nProtocolV05UpgradeTime);
+            else
+                printf(" Upgrade Info: v0.5+ no txdb upgrade detected.\n");
+        }
+        else
+        {
+            nProtocolV05UpgradeTime = GetTime();
+            printf(" Upgrade Info: upgrading txdb to v0.5 at timestamp %u\n", nProtocolV05UpgradeTime);
+            if (!txdb.WriteV05UpgradeTime(nProtocolV05UpgradeTime))
+                return error("LoadBlockIndex() : failed to write upgrade info");
+        }
+        txdb.Close();
+    }
+
     return true;
 }
 
@@ -2556,7 +2579,15 @@ string GetWarnings(string strFor)
     if (IsProtocolV04(nProtocolV04UpgradeTime + 60*60*24)) // 1 day margin
     {
         nPriority = 5000;
-        strStatusBar = strRPC = "WARNING: Blockchain redownload required approaching or past v0.4 upgrade deadline.";
+        strStatusBar = strRPC = "WARNING: Blockchain redownload required upgrading from pre v0.4 wallet.";
+    }
+    else if (IsProtocolV05(nProtocolV05UpgradeTime + 60*60*24)) // 1 day margin
+    {
+        // v0.5 protocol does not change modifier computation from v0.4.
+        // So redownload of blockchain is not required for late upgrades, 
+        // but still recommended.
+        nPriority = 200;
+        strStatusBar = strRPC = "WARNING: Blockchain redownload recommended approaching or past v0.5 upgrade deadline.";
     }
 
     // Alerts

src/version.h

@@ -43,7 +43,7 @@ static const int PPCOIN_VERSION =
 // network protocol versioning
 //
 
-static const int PROTOCOL_VERSION = 60004;
+static const int PROTOCOL_VERSION = 60005;
 
 // earlier versions not supported as of Feb 2012, and are disconnected
 // NOTE: as of bitcoin v0.6 message serialization (vSend, vRecv) still