PoS improvements

src/Makefile.am

@@ -191,6 +191,7 @@ BITCOIN_CORE_H = \
   pow.h \
   primitives/block.h \
   primitives/transaction.h \
+  primitives/nonce.h \
   protocol.h \
   pubkey.h \
   random.h \
@@ -415,6 +416,7 @@ libbitcoin_common_a_SOURCES = \
   netbase.cpp \
   primitives/block.cpp \
   primitives/transaction.cpp \
+  primitives/nonce.cpp \
   protocol.cpp \
   pubkey.cpp \
   scheduler.cpp \
@@ -624,6 +626,7 @@ libzcashconsensus_la_SOURCES = \
   crypto/sha512.cpp \
   hash.cpp \
   primitives/transaction.cpp \
+  primitives/nonce.cpp \
   pubkey.cpp \
   script/zcashconsensus.cpp \
   script/interpreter.cpp \

src/komodo_bitcoind.h

@@ -1258,7 +1258,7 @@ int32_t komodo_is_PoSblock(int32_t slowflag,int32_t height,CBlock *pblock,arith_
     return(isPoS);
 }
 
-// if slow flag is 1, this does a slower check that checks the target with consensus, otherwise quick, insecure check for internal integrity
+// for now, we will ignore slowFlag in the interest of keeping success/fail simpler for security purposes
 bool verusCheckPOSBlock(int32_t slowflag, CBlock *pblock, int32_t height)
 {
     CBlockIndex *pastBlockIndex;
@@ -1275,11 +1275,11 @@ bool verusCheckPOSBlock(int32_t slowflag, CBlock *pblock, int32_t height)
 
     char voutaddr[64], destaddr[64], cbaddr[64];
 
-    target.SetCompact(pblock->GetVerusPOSTarget());
     txn_count = pblock->vtx.size();
 
     if ( txn_count > 1 )
     {
+        target.SetCompact(pblock->GetVerusPOSTarget());
         txid = pblock->vtx[txn_count-1].vin[0].prevout.hash;
         voutNum = pblock->vtx[txn_count-1].vin[0].prevout.n;
 
@@ -1291,20 +1291,28 @@ bool verusCheckPOSBlock(int32_t slowflag, CBlock *pblock, int32_t height)
         {
             fprintf(stderr,"ERROR: invalid PoS block %s - no transaction\n",blkHash.ToString().c_str());
         }
-        else if (!(pastBlockIndex = komodo_chainactive(height - COINBASE_MATURITY)))
+        else if (!(pastBlockIndex = komodo_chainactive(height - 100)))
         {
-            fprintf(stderr,"ERROR: invalid PoS block %s - no past block found\n",blkHash.ToString().c_str());
+            fprintf(stderr,"WARNING: chain not fully loaded or invalid PoS block %s - no past block found\n",blkHash.ToString().c_str());
         }
         else
         {
-            hash = UintToArith256(tx.GetVerusPOSHash(voutNum, height, pastBlockIndex->GetBlockHash()));
+            CBlockHeader bh = pastBlockIndex->GetBlockHeader();
+            uint256 pastHash = bh.GetVerusEntropyHash(height);
+
+            // if height is over when Nonce is required to be the new format, we check that the new format is correct
+            // if over when we have the new POS hash function, we validate that as well
+            // they are 100 blocks apart
+            CPOSNonce nonce = pblock->nNonce;
+
+            hash = UintToArith256(tx.GetVerusPOSHash(&nonce, voutNum, height, pastHash));
             if (hash <= target)
             {
                 if ((mapBlockIndex.count(blkHash) == 0) ||
                     !(pastBlockIndex = mapBlockIndex[blkHash]) || 
                     (height - pastBlockIndex->nHeight) < VERUS_MIN_STAKEAGE)
                 {
-                    fprintf(stderr,"ERROR: invalid PoS block %s - no prev block found\n",blkHash.ToString().c_str());
+                    fprintf(stderr,"ERROR: invalid PoS block %s - stake transaction too new\n",blkHash.ToString().c_str());
                 }
                 else if ( slowflag != 0 )
                 {
@@ -1317,13 +1325,24 @@ bool verusCheckPOSBlock(int32_t slowflag, CBlock *pblock, int32_t height)
                     else
                     {
                         arith_uint256 cTarget;
-                        cTarget.SetCompact(lwmaGetNextPOSRequired(previndex, Params().GetConsensus()));
+                        uint32_t nBits = lwmaGetNextPOSRequired(previndex, Params().GetConsensus());
+                        cTarget.SetCompact(nBits);
+                        bool nonceOK = true;
 
-                        if (cTarget != target)
+                        if (CPOSNonce::NewNonceActive(height) && !nonce.CheckPOSEntropy(pastHash, txid, voutNum))
                         {
-                            fprintf(stderr,"ERROR: invalid PoS block %s - invalid diff target\n",blkHash.ToString().c_str());
+                            fprintf(stderr,"ERROR: invalid PoS block %s - nonce entropy corrupted or forged\n",blkHash.ToString().c_str());
+                            nonceOK = false;
                         }
-                        else if ( ExtractDestination(pblock->vtx[txn_count-1].vout[0].scriptPubKey, voutaddress) &&
+                        else
+                        {
+                            if (cTarget != target)
+                            {
+                                fprintf(stderr,"ERROR: invalid PoS block %s - invalid diff target\n",blkHash.ToString().c_str());
+                                nonceOK = false;
+                            }
+                        }
+                        if ( nonceOK && ExtractDestination(pblock->vtx[txn_count-1].vout[0].scriptPubKey, voutaddress) &&
                                   ExtractDestination(tx.vout[voutNum].scriptPubKey, destaddress) &&
                                   CScriptExt::ExtractVoutDestination(pblock->vtx[0], 0, cbaddress) )
                         {

src/main.cpp

@@ -3149,7 +3149,7 @@ bool static DisconnectTip(CValidationState &state, bool fBare = false) {
             list<CTransaction> removed;
             CValidationState stateDummy;
             // don't keep staking or invalid transactions
-            if (tx.IsCoinBase() || (block.IsVerusPOSBlock() && (i == (block.vtx.size() - 1))) || !AcceptToMemoryPool(mempool, stateDummy, tx, false, NULL))
+            if (tx.IsCoinBase() || ((i == (block.vtx.size() - 1)) && block.IsVerusPOSBlock()) || !AcceptToMemoryPool(mempool, stateDummy, tx, false, NULL))
             {
                 mempool.remove(tx, removed, true);
             }
@@ -3171,7 +3171,7 @@ bool static DisconnectTip(CValidationState &state, bool fBare = false) {
     for (int i = 0; i < block.vtx.size(); i++)
     {
         CTransaction &tx = block.vtx[i];
-        if (block.IsVerusPOSBlock() && (i == (block.vtx.size() - 1)))
+        if ((i == (block.vtx.size() - 1) && block.IsVerusPOSBlock()))
         {
             EraseFromWallets(tx.GetHash());
         }

src/miner.cpp

@@ -128,7 +128,7 @@ int32_t komodo_validate_interest(const CTransaction &tx,int32_t txheight,uint32_
 int64_t komodo_block_unlocktime(uint32_t nHeight);
 uint64_t komodo_commission(const CBlock *block);
 int32_t komodo_staked(CPubKey &pubkey, CMutableTransaction &txNew,uint32_t nBits,uint32_t *blocktimep,uint32_t *txtimep,uint256 *utxotxidp,int32_t *utxovoutp,uint64_t *utxovaluep,uint8_t *utxosig);
-int32_t verus_staked(CPubKey &pubkey, CMutableTransaction &txNew, uint32_t &nBits, arith_uint256 &hashResult, uint8_t *utxosig);
+int32_t verus_staked(CBlock *pBlock, CPubKey &pubkey, CMutableTransaction &txNew, uint32_t &nBits, arith_uint256 &hashResult, uint8_t *utxosig);
 int32_t komodo_notaryvin(CMutableTransaction &txNew,uint8_t *notarypub33);
 
 CBlockTemplate* CreateNewBlock(const CScript& _scriptPubKeyIn, bool isStake)
@@ -462,7 +462,7 @@ CBlockTemplate* CreateNewBlock(const CScript& _scriptPubKeyIn, bool isStake)
             {
                 uint32_t nBitsPOS;
                 arith_uint256 posHash;
-                siglen = verus_staked(key, txStaked, nBitsPOS, posHash, utxosig);
+                siglen = verus_staked(pblock, key, txStaked, nBitsPOS, posHash, utxosig);
                 blocktime = GetAdjustedTime();
                 pblock->SetVerusPOSTarget(nBitsPOS);
 
@@ -959,7 +959,7 @@ void static VerusStaker(CWallet *pwallet)
             printf("staking reward %.8f %s!\n", (double)subsidy / (double)COIN, ASSETCHAINS_SYMBOL);
             arith_uint256 post;
             post.SetCompact(pblock->GetVerusPOSTarget());
-            printf("  hash: %s  \ntarget: %s\n", pblock->vtx[pblock->vtx.size()-1].GetVerusPOSHash(0, Mining_height, pindexPrev->GetBlockHash()).GetHex().c_str(), ArithToUint256(post).GetHex().c_str());
+            printf("  hash: %s  \ntarget: %s\n", pblock->vtx[pblock->vtx.size()-1].GetVerusPOSHash(&(pblock->nNonce), 0, Mining_height, pindexPrev->GetBlockHeader().GetVerusEntropyHash(Mining_height)).GetHex().c_str(), ArithToUint256(post).GetHex().c_str());
             if (unlockTime > Mining_height && subsidy >= ASSETCHAINS_TIMELOCKGTE)
                 printf("- timelocked until block %i\n", unlockTime);
             else

src/primitives/block.cpp

@@ -10,6 +10,8 @@
 #include "utilstrencodings.h"
 #include "crypto/common.h"
 
+extern uint32_t ASSETCHAINS_ALGO, ASSETCHAINS_VERUSHASH;
+
 // default hash algorithm for block
 uint256 (CBlockHeader::*CBlockHeader::hashFunction)() const = &CBlockHeader::GetSHA256DHash;
 
@@ -43,6 +45,47 @@ void CBlockHeader::SetVerusHash()
     CBlockHeader::hashFunction = &CBlockHeader::GetVerusHash;
 }
 
+// returns false if unable to fast calculate the VerusPOSHash from the header. it can still be calculated from the block
+// in that case
+bool CBlockHeader::GetVerusPOSHash(uint256 &value, int32_t nHeight) const
+{
+    // if below the required height or no storage space in the solution, we can't get
+    // a cached txid value to calculate the POSHash from the header
+    if (!(CPOSNonce::NewNonceActive(nHeight) && IsVerusPOSBlock()))
+        return false;
+    
+    // if we can calculate, this assumes the protocol that the POSHash calculation is:
+    //    hashWriter << ASSETCHAINS_MAGIC;
+    //    hashWriter << nNonce; (nNonce is:
+    //                           (high 128 bits == low 128 bits of verus hash of low 128 bits of nonce)
+    //                           (low 32 bits == compact PoS difficult)
+    //                           (mid 96 bits == low 96 bits of HASH(pastHash, txid, voutnum)
+    //                              pastHash is hash of height - 100, either PoW hash of block or PoS hash, if new PoS
+    //                          )
+    //    hashWriter << height;
+    //    return hashWriter.GetHash();
+    CVerusHashWriter hashWriter  = CVerusHashWriter(SER_GETHASH, PROTOCOL_VERSION);
+
+    hashWriter << ASSETCHAINS_MAGIC;
+    hashWriter << nNonce;
+    hashWriter << nHeight;
+    value = hashWriter.GetHash();
+    return true;
+}
+
+// depending on the height of the block and its type, this returns the POS hash or the POW hash
+uint256 CBlockHeader::GetVerusEntropyHash(int32_t height) const
+{
+    uint256 retVal;
+    // if we qualify as PoW, use PoW hash, regardless of PoS state
+    if (GetVerusPOSHash(retVal, height))
+    {
+        // POS hash
+        return retVal;
+    }
+    return GetHash();
+}
+
 uint256 CBlock::BuildMerkleTree(bool* fMutated) const
 {
     /* WARNING! If you're reading this because you're learning about crypto

src/primitives/block.h

@@ -7,6 +7,7 @@
 #define BITCOIN_PRIMITIVES_BLOCK_H
 
 #include "primitives/transaction.h"
+#include "primitives/nonce.h"
 #include "serialize.h"
 #include "uint256.h"
 #include "arith_uint256.h"
@@ -33,7 +34,7 @@ public:
     uint256 hashReserved;
     uint32_t nTime;
     uint32_t nBits;
-    uint256 nNonce;
+    CPOSNonce nNonce;
     std::vector<unsigned char> nSolution;
 
     CBlockHeader()
@@ -84,6 +85,9 @@ public:
     uint256 GetVerusHash() const;
     static void SetVerusHash();
 
+    bool GetVerusPOSHash(uint256 &value, int32_t nHeight) const;
+    uint256 GetVerusEntropyHash(int32_t nHeight) const;
+
     uint256 GetVerusV2Hash() const;
 
     int64_t GetBlockTime() const
@@ -105,11 +109,7 @@ public:
 
     bool IsVerusPOSBlock() const
     {
-        arith_uint256 arNonce = UintToArith256(nNonce);
+        return nNonce.IsPOSNonce();
-        arith_uint256 tmpNonce = ((arNonce << 128) >> 128);
-        CVerusHashWriter hashWriter = CVerusHashWriter(SER_GETHASH, PROTOCOL_VERSION);
-        hashWriter << ArithToUint256(tmpNonce);
-        return (nNonce == ArithToUint256(UintToArith256(hashWriter.GetHash()) << 128 | tmpNonce));
     }
 
     void SetVerusPOSTarget(int32_t nBits)

src/primitives/nonce.cpp

@@ -0,0 +1,68 @@
+// Copyright (c) 2018 Michael Toutonghi
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include "hash.h"
+#include "nonce.h"
+#include <cstring>
+
+extern char ASSETCHAINS_SYMBOL[65];
+
+bool CPOSNonce::NewPOSActive(int32_t height)
+{
+    if ((strcmp(ASSETCHAINS_SYMBOL, "VRSC") == 0) || (height < (96480 + 100)))
+        return false;
+    else if ((strcmp(ASSETCHAINS_SYMBOL, "VRSCTEST") == 0) && (height < (1000 + 100)))
+        return false;
+    else
+        return true;
+}
+
+bool CPOSNonce::NewNonceActive(int32_t height)
+{
+    if ((strcmp(ASSETCHAINS_SYMBOL, "VRSC") == 0) || (height < 96480))
+        return false;
+    else if ((strcmp(ASSETCHAINS_SYMBOL, "VRSCTEST") == 0) && (height < 1000))
+        return false;
+    else
+        return true;
+}
+
+void CPOSNonce::SetPOSEntropy(const uint256 &pastHash, uint256 txid, int32_t voutNum)
+{
+    // get low 96 bits of past hash and put it in top 96 bits of low 128 bits of nonce
+    CVerusHashWriter hashWriter = CVerusHashWriter(SER_GETHASH, PROTOCOL_VERSION);
+
+    // first hash the pastHash, txid, and voutNum, to create a combined 96 bits, which will be used in the nonce
+    hashWriter << pastHash;
+    hashWriter << txid;
+    hashWriter << voutNum;
+
+    arith_uint256 arNonce = (UintToArith256(*this) & 0xffffffff) |
+        ((UintToArith256(hashWriter.GetHash()) & UintToArith256(uint256S("0000000000000000000000000000000000000000ffffffffffffffffffffffff"))) << 32);
+
+    hashWriter = CVerusHashWriter(SER_GETHASH, PROTOCOL_VERSION);
+    hashWriter << ArithToUint256(arNonce);
+
+    *this = CPOSNonce(ArithToUint256(UintToArith256(hashWriter.GetHash()) << 128 | arNonce));
+}
+
+bool CPOSNonce::CheckPOSEntropy(const uint256 &pastHash, uint256 txid, int32_t voutNum)
+{
+    // get low 96 bits of past hash and put it in top 96 bits of low 128 bits of nonce
+    CVerusHashWriter hashWriter = CVerusHashWriter(SER_GETHASH, PROTOCOL_VERSION);
+
+    // first hash the pastHash, txid, and voutNum, to create a combined 96 bits, which will be used in the nonce
+    hashWriter << pastHash;
+    hashWriter << txid;
+    hashWriter << voutNum;
+
+    arith_uint256 arNonce = (UintToArith256(*this) & 0xffffffff) |
+        ((UintToArith256(hashWriter.GetHash()) & UintToArith256(uint256S("0000000000000000000000000000000000000000ffffffffffffffffffffffff"))) << 32);
+
+    hashWriter = CVerusHashWriter(SER_GETHASH, PROTOCOL_VERSION);
+    hashWriter << ArithToUint256(arNonce);
+
+    return UintToArith256(*this) == (UintToArith256(hashWriter.GetHash()) << 128 | arNonce);
+}
+

src/primitives/nonce.h

@@ -0,0 +1,66 @@
+// Copyright (c) 2018 Michael Toutonghi
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_PRIMITIVES_NONCE_H
+#define BITCOIN_PRIMITIVES_NONCE_H
+
+#include "serialize.h"
+#include "uint256.h"
+#include "arith_uint256.h"
+
+
+/** For POS blocks, the nNonce of a block header holds the entropy source for the POS contest
+ * in the latest VerusHash protocol, implemented at block below
+ * 
+ * */
+class CPOSNonce : public uint256
+{
+public:
+    static bool NewPOSActive(int32_t height);
+    static bool NewNonceActive(int32_t height);
+
+    CPOSNonce() {}
+    CPOSNonce(const base_blob<256> &b) : uint256(b) {}
+    CPOSNonce(const std::vector<unsigned char> &vch) : uint256(vch) {}
+
+    int32_t GetPOSTarget() const
+    {
+        uint32_t nBits = 0;
+
+        for (const unsigned char *p = begin() + 3; p >= begin(); p--)
+        {
+            nBits <<= 8;
+            nBits += *p;
+        }
+        return nBits;
+    }
+
+    bool IsPOSNonce() const
+    {
+        arith_uint256 arNonce = UintToArith256(*this);
+        arith_uint256 tmpNonce = ((arNonce << 128) >> 128);
+        CVerusHashWriter hashWriter = CVerusHashWriter(SER_GETHASH, PROTOCOL_VERSION);
+        hashWriter << ArithToUint256(tmpNonce);
+        return (*this == ArithToUint256(UintToArith256(hashWriter.GetHash()) << 128 | tmpNonce));
+    }
+
+    void SetPOSTarget(int32_t nBits)
+    {
+        CVerusHashWriter hashWriter = CVerusHashWriter(SER_GETHASH, PROTOCOL_VERSION);
+        arith_uint256 tmpNonce;
+
+        arith_uint256 arNonce = UintToArith256(*this);
+        arNonce = ((arNonce >> 32) << 32) | nBits;
+
+        tmpNonce = ((arNonce << 128) >> 128);
+        hashWriter << ArithToUint256(tmpNonce);
+
+        (uint256 &)(*this) = ArithToUint256(UintToArith256(hashWriter.GetHash()) << 128 | tmpNonce);
+    }
+
+    void SetPOSEntropy(const uint256 &pastHash, uint256 txid, int32_t voutNum);
+    bool CheckPOSEntropy(const uint256 &pastHash, uint256 txid, int32_t voutNum);
+};
+
+#endif // BITCOIN_PRIMITIVES_NONCE_H

src/primitives/transaction.h

@@ -14,6 +14,7 @@
 #include "arith_uint256.h"
 #include "consensus/consensus.h"
 #include "hash.h"
+#include "nonce.h"
 
 #ifndef __APPLE__
 #include <stdint.h>
@@ -474,25 +475,39 @@ public:
     }
 
     // verus hash will be the same for a given txid, output number, block height, and blockhash of 100 blocks past
-    static uint256 _GetVerusPOSHash(const uint256 &txid, int32_t voutNum, int32_t height, const uint256 &pastHash, int64_t value)
+    static uint256 _GetVerusPOSHash(CPOSNonce *pNonce, const uint256 &txid, int32_t voutNum, int32_t height, const uint256 &pastHash, int64_t value)
     {
+        pNonce->SetPOSEntropy(pastHash, txid, voutNum);
         CVerusHashWriter hashWriter  = CVerusHashWriter(SER_GETHASH, PROTOCOL_VERSION);
 
         hashWriter << ASSETCHAINS_MAGIC;
-        hashWriter << pastHash;
+
-        hashWriter << height;
+        // we only use the new style of POS hash after changeover and 100 blocks of enforced proper nonce updating
-        hashWriter << txid;
+        if (CPOSNonce::NewPOSActive(height))
-        hashWriter << voutNum;
+        {
-        return hashWriter.GetHash();
+            hashWriter << *pNonce;
+            hashWriter << height;
+            return hashWriter.GetHash();
+        }
+        else
+        {
+            hashWriter << pastHash;
+            hashWriter << height;
+            hashWriter << txid;
+            hashWriter << voutNum;
+            return hashWriter.GetHash();
+        }
     }
 
-    uint256 GetVerusPOSHash(int32_t voutNum, int32_t height, const uint256 &pastHash) const
+    // Nonce is modified to include the transaction information
+    uint256 GetVerusPOSHash(CPOSNonce *pNonce, int32_t voutNum, int32_t height, const uint256 &pastHash) const
     {
         uint256 txid = GetHash();
+
         if (voutNum >= vout.size())
             return uint256S("ff0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f");
 
-        return ArithToUint256(UintToArith256(_GetVerusPOSHash(txid, voutNum, height, pastHash, (uint64_t)vout[voutNum].nValue)) / vout[voutNum].nValue);
+        return ArithToUint256(UintToArith256(_GetVerusPOSHash(pNonce, txid, voutNum, height, pastHash, (uint64_t)vout[voutNum].nValue)) / vout[voutNum].nValue);
     }
 
     std::string ToString() const;

src/wallet/rpcwallet.cpp

@@ -4667,7 +4667,7 @@ int32_t komodo_staked(CPubKey &pubkey, CMutableTransaction &txNew,uint32_t nBits
     return(siglen);
 }
 
-int32_t verus_staked(CPubKey &pubkey, CMutableTransaction &txNew, uint32_t &nBits, arith_uint256 &hashResult, uint8_t *utxosig)
+int32_t verus_staked(CBlock *pBlock, CPubKey &pubkey, CMutableTransaction &txNew, uint32_t &nBits, arith_uint256 &hashResult, uint8_t *utxosig)
 {
-    return pwalletMain->VerusStakeTransaction(txNew, nBits, hashResult, utxosig);
+    return pwalletMain->VerusStakeTransaction(pBlock, txNew, nBits, hashResult, utxosig);
 }

src/wallet/wallet.cpp

@@ -998,8 +998,9 @@ CWallet::TxItems CWallet::OrderedTxItems(std::list<CAccountingEntry>& acentries,
 // UTXO with the smallest coin age if there is more than one, as larger coin age will win more often and is worth saving
 // each attempt consists of taking a VerusHash of the following values:
 //  ASSETCHAINS_MAGIC, nHeight, txid, voutNum
-bool CWallet::VerusSelectStakeOutput(arith_uint256 &hashResult, CTransaction &stakeSource, int32_t &voutNum, int32_t nHeight, const arith_uint256 &target) const
+bool CWallet::VerusSelectStakeOutput(CBlock *pBlock, arith_uint256 &hashResult, CTransaction &stakeSource, int32_t &voutNum, int32_t nHeight, uint32_t bnTarget) const
 {
+    arith_uint256 target;
     arith_uint256 curHash;
     vector<COutput> vecOutputs;
     COutput *pwinner = NULL;
@@ -1007,15 +1008,19 @@ bool CWallet::VerusSelectStakeOutput(arith_uint256 &hashResult, CTransaction &st
     txnouttype whichType;
     std:vector<std::vector<unsigned char>> vSolutions;
 
+    pBlock->nNonce.SetPOSTarget(bnTarget);
+    target.SetCompact(bnTarget);
+
     pwalletMain->AvailableCoins(vecOutputs, true, NULL, false, false);
 
-    if (pastBlockIndex = komodo_chainactive(nHeight - COINBASE_MATURITY))
+    if (pastBlockIndex = komodo_chainactive(nHeight - 100))
     {
-        uint256 pastHash = pastBlockIndex->GetBlockHash();
+        CBlockHeader bh = pastBlockIndex->GetBlockHeader();
+        uint256 pastHash = bh.GetVerusEntropyHash(nHeight);
 
         BOOST_FOREACH(COutput &txout, vecOutputs)
         {
-            if (txout.fSpendable && (UintToArith256(txout.tx->GetVerusPOSHash(txout.i, nHeight, pastHash)) <= target) && (txout.nDepth >= VERUS_MIN_STAKEAGE))
+            if (txout.fSpendable && (UintToArith256(txout.tx->GetVerusPOSHash(&(pBlock->nNonce), txout.i, nHeight, pastHash)) <= target) && (txout.nDepth >= VERUS_MIN_STAKEAGE))
             {
                 // get the smallest winner
                 if (Solver(txout.tx->vout[txout.i].scriptPubKey, whichType, vSolutions) && (whichType == TX_PUBKEY || whichType == TX_PUBKEYHASH) &&
@@ -1033,9 +1038,8 @@ bool CWallet::VerusSelectStakeOutput(arith_uint256 &hashResult, CTransaction &st
     return false;
 }
 
-int32_t CWallet::VerusStakeTransaction(CMutableTransaction &txNew, uint32_t &bnTarget, arith_uint256 &hashResult, uint8_t *utxosig) const
+int32_t CWallet::VerusStakeTransaction(CBlock *pBlock, CMutableTransaction &txNew, uint32_t bnTarget, arith_uint256 &hashResult, uint8_t *utxosig) const
 {
-    arith_uint256 target;
     CTransaction stakeSource;
     int32_t voutNum, siglen = 0;
     int64_t nValue;
@@ -1048,12 +1052,11 @@ int32_t CWallet::VerusStakeTransaction(CMutableTransaction &txNew, uint32_t &bnT
         tipindex = chainActive.Tip();
     }
     bnTarget = lwmaGetNextPOSRequired(tipindex, Params().GetConsensus());
-    target.SetCompact(bnTarget);
 
-    if (!VerusSelectStakeOutput(hashResult, stakeSource, voutNum, tipindex->nHeight + 1, target) ||
+    if (!VerusSelectStakeOutput(pBlock, hashResult, stakeSource, voutNum, tipindex->nHeight + 1, bnTarget) ||
         !Solver(stakeSource.vout[voutNum].scriptPubKey, whichType, vSolutions))
     {
-        LogPrintf("No eligible staking transaction found\n");
+        LogPrintf("Searched for eligible staking transactions, no winners found\n");
         return 0;
     }
 

src/wallet/wallet.h

@@ -1149,8 +1149,8 @@ public:
                           bool ignoreUnspendable=true);
     
     // staking functions
-    bool VerusSelectStakeOutput(arith_uint256 &hashResult, CTransaction &stakeSource, int32_t &voutNum, int32_t nHeight, const arith_uint256 &target) const;
+    bool VerusSelectStakeOutput(CBlock *pBlock, arith_uint256 &hashResult, CTransaction &stakeSource, int32_t &voutNum, int32_t nHeight, uint32_t bnTarget) const;
-    int32_t VerusStakeTransaction(CMutableTransaction &txNew, uint32_t &bnTarget, arith_uint256 &hashResult, uint8_t *utxosig) const;
+    int32_t VerusStakeTransaction(CBlock *pBlock, CMutableTransaction &txNew, uint32_t bnTarget, arith_uint256 &hashResult, uint8_t *utxosig) const;
 };
 
 /** A key allocated from the key pool. */