add pos_kernel base functionality

src/Makefile.am

@@ -167,6 +167,7 @@ BITCOIN_CORE_H = \
   policy/policy.h \
   policy/rbf.h \
   policy/settings.h \
+  pos_kernel.h \
   pow.h \
   protocol.h \
   psbt.h \
@@ -286,6 +287,7 @@ libbitcoin_server_a_SOURCES = \
   policy/fees.cpp \
   policy/rbf.cpp \
   policy/settings.cpp \
+  pos_kernel.cpp \
   pow.cpp \
   rest.cpp \
   rpc/blockchain.cpp \

src/pos_kernel.cpp

@@ -0,0 +1,53 @@
+#include <pos_kernel.h>
+#include <wallet/wallet.h>
+#include <txdb.h>
+#include <validation.h>
+#include <arith_uint256.h>
+
+namespace pos {
+
+    uint256 CalcKernelHash(uint256 stakeModifier, int64_t coinstakeTime, const COutPoint& prevout,
+                           const Consensus::Params& params) {
+        // Calculate hash
+        CDataStream ss(SER_GETHASH, 0);
+        ss << stakeModifier << coinstakeTime << prevout.hash << prevout.n;
+        return Hash(ss.begin(), ss.end());
+    }
+
+    CheckKernelHashRes
+    CheckKernelHash(uint256 stakeModifier, uint32_t nBits, int64_t coinstakeTime, CAmount coinstakeAmount,
+                    const COutPoint& prevout, const Consensus::Params& params) {
+        if (prevout.IsNull() || coinstakeAmount <= 0) {
+            return {false, arith_uint256{}};
+        }
+
+        // Base target
+        arith_uint256 targetProofOfStake;
+        targetProofOfStake.SetCompact(nBits);
+
+        const arith_uint256 hashProofOfStake = UintToArith256(
+                CalcKernelHash(stakeModifier, coinstakeTime, prevout, params));
+
+        // Now check if proof-of-stake hash meets target protocol
+        if ((hashProofOfStake / (uint64_t) coinstakeAmount) > targetProofOfStake) {
+            return {false, hashProofOfStake};
+        }
+
+        return {true, hashProofOfStake};
+    }
+
+    uint256 ComputeStakeModifier_PoS(uint256 prevStakeModifier, const COutPoint& prevout) {
+        // Calculate hash
+        CDataStream ss(SER_GETHASH, 0);
+        ss << prevStakeModifier << prevout.hash << prevout.n;
+        return Hash(ss.begin(), ss.end());
+    }
+
+    uint256 ComputeStakeModifier_PoW(uint256 prevStakeModifier, const uint256& prevBlockHash) {
+        // Calculate hash
+        CDataStream ss(SER_GETHASH, 0);
+        ss << prevStakeModifier << prevBlockHash;
+        return Hash(ss.begin(), ss.end());
+    }
+
+}

src/pos_kernel.h

@@ -0,0 +1,47 @@
+#pragma once
+
+#include <uint256.h>
+#include <arith_uint256.h>
+#include <consensus/params.h>
+#include <streams.h>
+#include <amount.h>
+
+class CWallet;
+
+class COutPoint;
+
+class CBlock;
+
+class CTransaction;
+
+class CCoinsViewCache;
+
+namespace pos {
+
+    struct CheckKernelHashRes {
+        bool hashOk;
+        arith_uint256 hashProofOfStake;
+    };
+
+/// Calculate PoS kernel hash
+    uint256
+    CalcKernelHash(uint256 stakeModifier, int64_t coinstakeTime, const COutPoint& prevout, const Consensus::Params& params);
+
+/// Check whether stake kernel meets hash target
+/// Sets hashProofOfStake, hashOk is true of the kernel meets hash target
+    CheckKernelHashRes
+    CheckKernelHash(uint256 stakeModifier, uint32_t nBits, int64_t coinstakeTime, CAmount coinstakeAmount,
+                    const COutPoint& prevout, const Consensus::Params& params);
+
+/// Stake Modifier (hash modifier of proof-of-stake):
+/// The purpose of stake modifier is to prevent a txout (coin) owner from
+/// computing future proof-of-stake generated by this txout at the time
+/// of transaction confirmation. To meet kernel protocol, the txout
+/// must hash with a future stake modifier to generate the proof.
+    uint256 ComputeStakeModifier_PoS(uint256 prevStakeModifier, const COutPoint& prevout);
+
+/// Theoretically, blockHash can be used by miner to make next PoS block easier for him.
+/// However, PoW blocks are not supported in mainnet.
+    uint256 ComputeStakeModifier_PoW(uint256 prevStakeModifier, const uint256& prevBlockHash);
+
+}