diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
index 1b8a5728ae..ddd354454c 100644
--- a/src/script/interpreter.cpp
+++ b/src/script/interpreter.cpp
@@ -1,1675 +1,1677 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
 // Copyright (c) 2009-2016 The Bitcoin Core developers
 // Copyright (c) 2017-2018 The Bitcoin developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <script/interpreter.h>
 
 #include <crypto/ripemd160.h>
 #include <crypto/sha1.h>
 #include <crypto/sha256.h>
 #include <primitives/transaction.h>
 #include <pubkey.h>
 #include <script/script.h>
 #include <script/script_flags.h>
 #include <script/sigencoding.h>
 #include <uint256.h>
 
 bool CastToBool(const valtype &vch) {
     for (size_t i = 0; i < vch.size(); i++) {
         if (vch[i] != 0) {
             // Can be negative zero
             if (i == vch.size() - 1 && vch[i] == 0x80) {
                 return false;
             }
             return true;
         }
     }
     return false;
 }
 
 /**
  * Script is a stack machine (like Forth) that evaluates a predicate
  * returning a bool indicating valid or not.  There are no loops.
  */
 #define stacktop(i) (stack.at(stack.size() + (i)))
 #define altstacktop(i) (altstack.at(altstack.size() + (i)))
 static inline void popstack(std::vector<valtype> &stack) {
     if (stack.empty()) {
         throw std::runtime_error("popstack(): stack empty");
     }
     stack.pop_back();
 }
 
 static void CleanupScriptCode(CScript &scriptCode,
                               const std::vector<uint8_t> &vchSig,
                               uint32_t flags) {
     // Drop the signature in scripts when SIGHASH_FORKID is not used.
     SigHashType sigHashType = GetHashType(vchSig);
     if (!(flags & SCRIPT_ENABLE_SIGHASH_FORKID) || !sigHashType.hasForkId()) {
         scriptCode.FindAndDelete(CScript(vchSig));
     }
 }
 
 static bool CheckMinimalPush(const valtype &data, opcodetype opcode) {
+    // Excludes OP_1NEGATE, OP_1-16 since they are by definition minimal
+    assert(0 <= opcode && opcode <= OP_PUSHDATA4);
     if (data.size() == 0) {
-        // Could have used OP_0.
+        // Should have used OP_0.
         return opcode == OP_0;
     }
     if (data.size() == 1 && data[0] >= 1 && data[0] <= 16) {
-        // Could have used OP_1 .. OP_16.
-        return opcode == OP_1 + (data[0] - 1);
+        // Should have used OP_1 .. OP_16.
+        return false;
     }
     if (data.size() == 1 && data[0] == 0x81) {
-        // Could have used OP_1NEGATE.
-        return opcode == OP_1NEGATE;
+        // Should have used OP_1NEGATE.
+        return false;
     }
     if (data.size() <= 75) {
-        // Could have used a direct push (opcode indicating number of bytes
+        // Must have used a direct push (opcode indicating number of bytes
         // pushed + those bytes).
         return opcode == data.size();
     }
     if (data.size() <= 255) {
-        // Could have used OP_PUSHDATA.
+        // Must have used OP_PUSHDATA.
         return opcode == OP_PUSHDATA1;
     }
     if (data.size() <= 65535) {
-        // Could have used OP_PUSHDATA2.
+        // Must have used OP_PUSHDATA2.
         return opcode == OP_PUSHDATA2;
     }
     return true;
 }
 
 static bool IsOpcodeDisabled(opcodetype opcode, uint32_t flags) {
     switch (opcode) {
         case OP_INVERT:
         case OP_2MUL:
         case OP_2DIV:
         case OP_MUL:
         case OP_LSHIFT:
         case OP_RSHIFT:
             // Disabled opcodes.
             return true;
 
         default:
             break;
     }
 
     return false;
 }
 
 bool EvalScript(std::vector<valtype> &stack, const CScript &script,
                 uint32_t flags, const BaseSignatureChecker &checker,
                 ScriptError *serror) {
     static const CScriptNum bnZero(0);
     static const CScriptNum bnOne(1);
     static const valtype vchFalse(0);
     static const valtype vchTrue(1, 1);
 
     CScript::const_iterator pc = script.begin();
     CScript::const_iterator pend = script.end();
     CScript::const_iterator pbegincodehash = script.begin();
     opcodetype opcode;
     valtype vchPushValue;
     std::vector<bool> vfExec;
     std::vector<valtype> altstack;
     set_error(serror, ScriptError::UNKNOWN);
     if (script.size() > MAX_SCRIPT_SIZE) {
         return set_error(serror, ScriptError::SCRIPT_SIZE);
     }
     int nOpCount = 0;
     bool fRequireMinimal = (flags & SCRIPT_VERIFY_MINIMALDATA) != 0;
 
     try {
         while (pc < pend) {
             bool fExec = !count(vfExec.begin(), vfExec.end(), false);
 
             //
             // Read instruction
             //
             if (!script.GetOp(pc, opcode, vchPushValue)) {
                 return set_error(serror, ScriptError::BAD_OPCODE);
             }
             if (vchPushValue.size() > MAX_SCRIPT_ELEMENT_SIZE) {
                 return set_error(serror, ScriptError::PUSH_SIZE);
             }
 
             // Note how OP_RESERVED does not count towards the opcode limit.
             if (opcode > OP_16 && ++nOpCount > MAX_OPS_PER_SCRIPT) {
                 return set_error(serror, ScriptError::OP_COUNT);
             }
 
             // Some opcodes are disabled.
             if (IsOpcodeDisabled(opcode, flags)) {
                 return set_error(serror, ScriptError::DISABLED_OPCODE);
             }
 
             if (fExec && 0 <= opcode && opcode <= OP_PUSHDATA4) {
                 if (fRequireMinimal &&
                     !CheckMinimalPush(vchPushValue, opcode)) {
                     return set_error(serror, ScriptError::MINIMALDATA);
                 }
                 stack.push_back(vchPushValue);
             } else if (fExec || (OP_IF <= opcode && opcode <= OP_ENDIF)) {
                 switch (opcode) {
                     //
                     // Push value
                     //
                     case OP_1NEGATE:
                     case OP_1:
                     case OP_2:
                     case OP_3:
                     case OP_4:
                     case OP_5:
                     case OP_6:
                     case OP_7:
                     case OP_8:
                     case OP_9:
                     case OP_10:
                     case OP_11:
                     case OP_12:
                     case OP_13:
                     case OP_14:
                     case OP_15:
                     case OP_16: {
                         // ( -- value)
                         CScriptNum bn((int)opcode - (int)(OP_1 - 1));
                         stack.push_back(bn.getvch());
                         // The result of these opcodes should always be the
                         // minimal way to push the data they push, so no need
                         // for a CheckMinimalPush here.
                     } break;
 
                     //
                     // Control
                     //
                     case OP_NOP:
                         break;
 
                     case OP_CHECKLOCKTIMEVERIFY: {
                         if (!(flags & SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY)) {
                             // not enabled; treat as a NOP2
                             if (flags &
                                 SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS) {
                                 return set_error(
                                     serror,
                                     ScriptError::DISCOURAGE_UPGRADABLE_NOPS);
                             }
                             break;
                         }
 
                         if (stack.size() < 1) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
 
                         // Note that elsewhere numeric opcodes are limited to
                         // operands in the range -2**31+1 to 2**31-1, however it
                         // is legal for opcodes to produce results exceeding
                         // that range. This limitation is implemented by
                         // CScriptNum's default 4-byte limit.
                         //
                         // If we kept to that limit we'd have a year 2038
                         // problem, even though the nLockTime field in
                         // transactions themselves is uint32 which only becomes
                         // meaningless after the year 2106.
                         //
                         // Thus as a special case we tell CScriptNum to accept
                         // up to 5-byte bignums, which are good until 2**39-1,
                         // well beyond the 2**32-1 limit of the nLockTime field
                         // itself.
                         const CScriptNum nLockTime(stacktop(-1),
                                                    fRequireMinimal, 5);
 
                         // In the rare event that the argument may be < 0 due to
                         // some arithmetic being done first, you can always use
                         // 0 MAX CHECKLOCKTIMEVERIFY.
                         if (nLockTime < 0) {
                             return set_error(serror,
                                              ScriptError::NEGATIVE_LOCKTIME);
                         }
 
                         // Actually compare the specified lock time with the
                         // transaction.
                         if (!checker.CheckLockTime(nLockTime)) {
                             return set_error(serror,
                                              ScriptError::UNSATISFIED_LOCKTIME);
                         }
 
                         break;
                     }
 
                     case OP_CHECKSEQUENCEVERIFY: {
                         if (!(flags & SCRIPT_VERIFY_CHECKSEQUENCEVERIFY)) {
                             // not enabled; treat as a NOP3
                             if (flags &
                                 SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS) {
                                 return set_error(
                                     serror,
                                     ScriptError::DISCOURAGE_UPGRADABLE_NOPS);
                             }
                             break;
                         }
 
                         if (stack.size() < 1) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
 
                         // nSequence, like nLockTime, is a 32-bit unsigned
                         // integer field. See the comment in CHECKLOCKTIMEVERIFY
                         // regarding 5-byte numeric operands.
                         const CScriptNum nSequence(stacktop(-1),
                                                    fRequireMinimal, 5);
 
                         // In the rare event that the argument may be < 0 due to
                         // some arithmetic being done first, you can always use
                         // 0 MAX CHECKSEQUENCEVERIFY.
                         if (nSequence < 0) {
                             return set_error(serror,
                                              ScriptError::NEGATIVE_LOCKTIME);
                         }
 
                         // To provide for future soft-fork extensibility, if the
                         // operand has the disabled lock-time flag set,
                         // CHECKSEQUENCEVERIFY behaves as a NOP.
                         if ((nSequence &
                              CTxIn::SEQUENCE_LOCKTIME_DISABLE_FLAG) != 0) {
                             break;
                         }
 
                         // Compare the specified sequence number with the input.
                         if (!checker.CheckSequence(nSequence)) {
                             return set_error(serror,
                                              ScriptError::UNSATISFIED_LOCKTIME);
                         }
 
                         break;
                     }
 
                     case OP_NOP1:
                     case OP_NOP4:
                     case OP_NOP5:
                     case OP_NOP6:
                     case OP_NOP7:
                     case OP_NOP8:
                     case OP_NOP9:
                     case OP_NOP10: {
                         if (flags & SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS) {
                             return set_error(
                                 serror,
                                 ScriptError::DISCOURAGE_UPGRADABLE_NOPS);
                         }
                     } break;
 
                     case OP_IF:
                     case OP_NOTIF: {
                         // <expression> if [statements] [else [statements]]
                         // endif
                         bool fValue = false;
                         if (fExec) {
                             if (stack.size() < 1) {
                                 return set_error(
                                     serror,
                                     ScriptError::UNBALANCED_CONDITIONAL);
                             }
                             valtype &vch = stacktop(-1);
                             if (flags & SCRIPT_VERIFY_MINIMALIF) {
                                 if (vch.size() > 1) {
                                     return set_error(serror,
                                                      ScriptError::MINIMALIF);
                                 }
                                 if (vch.size() == 1 && vch[0] != 1) {
                                     return set_error(serror,
                                                      ScriptError::MINIMALIF);
                                 }
                             }
                             fValue = CastToBool(vch);
                             if (opcode == OP_NOTIF) {
                                 fValue = !fValue;
                             }
                             popstack(stack);
                         }
                         vfExec.push_back(fValue);
                     } break;
 
                     case OP_ELSE: {
                         if (vfExec.empty()) {
                             return set_error(
                                 serror, ScriptError::UNBALANCED_CONDITIONAL);
                         }
                         vfExec.back() = !vfExec.back();
                     } break;
 
                     case OP_ENDIF: {
                         if (vfExec.empty()) {
                             return set_error(
                                 serror, ScriptError::UNBALANCED_CONDITIONAL);
                         }
                         vfExec.pop_back();
                     } break;
 
                     case OP_VERIFY: {
                         // (true -- ) or
                         // (false -- false) and return
                         if (stack.size() < 1) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         bool fValue = CastToBool(stacktop(-1));
                         if (fValue) {
                             popstack(stack);
                         } else {
                             return set_error(serror, ScriptError::VERIFY);
                         }
                     } break;
 
                     case OP_RETURN: {
                         return set_error(serror, ScriptError::OP_RETURN);
                     } break;
 
                     //
                     // Stack ops
                     //
                     case OP_TOALTSTACK: {
                         if (stack.size() < 1) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         altstack.push_back(stacktop(-1));
                         popstack(stack);
                     } break;
 
                     case OP_FROMALTSTACK: {
                         if (altstack.size() < 1) {
                             return set_error(
                                 serror,
                                 ScriptError::INVALID_ALTSTACK_OPERATION);
                         }
                         stack.push_back(altstacktop(-1));
                         popstack(altstack);
                     } break;
 
                     case OP_2DROP: {
                         // (x1 x2 -- )
                         if (stack.size() < 2) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         popstack(stack);
                         popstack(stack);
                     } break;
 
                     case OP_2DUP: {
                         // (x1 x2 -- x1 x2 x1 x2)
                         if (stack.size() < 2) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         valtype vch1 = stacktop(-2);
                         valtype vch2 = stacktop(-1);
                         stack.push_back(vch1);
                         stack.push_back(vch2);
                     } break;
 
                     case OP_3DUP: {
                         // (x1 x2 x3 -- x1 x2 x3 x1 x2 x3)
                         if (stack.size() < 3) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         valtype vch1 = stacktop(-3);
                         valtype vch2 = stacktop(-2);
                         valtype vch3 = stacktop(-1);
                         stack.push_back(vch1);
                         stack.push_back(vch2);
                         stack.push_back(vch3);
                     } break;
 
                     case OP_2OVER: {
                         // (x1 x2 x3 x4 -- x1 x2 x3 x4 x1 x2)
                         if (stack.size() < 4) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         valtype vch1 = stacktop(-4);
                         valtype vch2 = stacktop(-3);
                         stack.push_back(vch1);
                         stack.push_back(vch2);
                     } break;
 
                     case OP_2ROT: {
                         // (x1 x2 x3 x4 x5 x6 -- x3 x4 x5 x6 x1 x2)
                         if (stack.size() < 6) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         valtype vch1 = stacktop(-6);
                         valtype vch2 = stacktop(-5);
                         stack.erase(stack.end() - 6, stack.end() - 4);
                         stack.push_back(vch1);
                         stack.push_back(vch2);
                     } break;
 
                     case OP_2SWAP: {
                         // (x1 x2 x3 x4 -- x3 x4 x1 x2)
                         if (stack.size() < 4) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         swap(stacktop(-4), stacktop(-2));
                         swap(stacktop(-3), stacktop(-1));
                     } break;
 
                     case OP_IFDUP: {
                         // (x - 0 | x x)
                         if (stack.size() < 1) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         valtype vch = stacktop(-1);
                         if (CastToBool(vch)) {
                             stack.push_back(vch);
                         }
                     } break;
 
                     case OP_DEPTH: {
                         // -- stacksize
                         CScriptNum bn(stack.size());
                         stack.push_back(bn.getvch());
                     } break;
 
                     case OP_DROP: {
                         // (x -- )
                         if (stack.size() < 1) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         popstack(stack);
                     } break;
 
                     case OP_DUP: {
                         // (x -- x x)
                         if (stack.size() < 1) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         valtype vch = stacktop(-1);
                         stack.push_back(vch);
                     } break;
 
                     case OP_NIP: {
                         // (x1 x2 -- x2)
                         if (stack.size() < 2) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         stack.erase(stack.end() - 2);
                     } break;
 
                     case OP_OVER: {
                         // (x1 x2 -- x1 x2 x1)
                         if (stack.size() < 2) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         valtype vch = stacktop(-2);
                         stack.push_back(vch);
                     } break;
 
                     case OP_PICK:
                     case OP_ROLL: {
                         // (xn ... x2 x1 x0 n - xn ... x2 x1 x0 xn)
                         // (xn ... x2 x1 x0 n - ... x2 x1 x0 xn)
                         if (stack.size() < 2) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         int n =
                             CScriptNum(stacktop(-1), fRequireMinimal).getint();
                         popstack(stack);
                         if (n < 0 || n >= (int)stack.size()) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         valtype vch = stacktop(-n - 1);
                         if (opcode == OP_ROLL) {
                             stack.erase(stack.end() - n - 1);
                         }
                         stack.push_back(vch);
                     } break;
 
                     case OP_ROT: {
                         // (x1 x2 x3 -- x2 x3 x1)
                         //  x2 x1 x3  after first swap
                         //  x2 x3 x1  after second swap
                         if (stack.size() < 3) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         swap(stacktop(-3), stacktop(-2));
                         swap(stacktop(-2), stacktop(-1));
                     } break;
 
                     case OP_SWAP: {
                         // (x1 x2 -- x2 x1)
                         if (stack.size() < 2) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         swap(stacktop(-2), stacktop(-1));
                     } break;
 
                     case OP_TUCK: {
                         // (x1 x2 -- x2 x1 x2)
                         if (stack.size() < 2) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         valtype vch = stacktop(-1);
                         stack.insert(stack.end() - 2, vch);
                     } break;
 
                     case OP_SIZE: {
                         // (in -- in size)
                         if (stack.size() < 1) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         CScriptNum bn(stacktop(-1).size());
                         stack.push_back(bn.getvch());
                     } break;
 
                     //
                     // Bitwise logic
                     //
                     case OP_AND:
                     case OP_OR:
                     case OP_XOR: {
                         // (x1 x2 - out)
                         if (stack.size() < 2) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         valtype &vch1 = stacktop(-2);
                         valtype &vch2 = stacktop(-1);
 
                         // Inputs must be the same size
                         if (vch1.size() != vch2.size()) {
                             return set_error(serror,
                                              ScriptError::INVALID_OPERAND_SIZE);
                         }
 
                         // To avoid allocating, we modify vch1 in place.
                         switch (opcode) {
                             case OP_AND:
                                 for (size_t i = 0; i < vch1.size(); ++i) {
                                     vch1[i] &= vch2[i];
                                 }
                                 break;
                             case OP_OR:
                                 for (size_t i = 0; i < vch1.size(); ++i) {
                                     vch1[i] |= vch2[i];
                                 }
                                 break;
                             case OP_XOR:
                                 for (size_t i = 0; i < vch1.size(); ++i) {
                                     vch1[i] ^= vch2[i];
                                 }
                                 break;
                             default:
                                 break;
                         }
 
                         // And pop vch2.
                         popstack(stack);
                     } break;
 
                     case OP_EQUAL:
                     case OP_EQUALVERIFY:
                         // case OP_NOTEQUAL: // use OP_NUMNOTEQUAL
                         {
                             // (x1 x2 - bool)
                             if (stack.size() < 2) {
                                 return set_error(
                                     serror,
                                     ScriptError::INVALID_STACK_OPERATION);
                             }
                             valtype &vch1 = stacktop(-2);
                             valtype &vch2 = stacktop(-1);
 
                             bool fEqual = (vch1 == vch2);
                             // OP_NOTEQUAL is disabled because it would be too
                             // easy to say something like n != 1 and have some
                             // wiseguy pass in 1 with extra zero bytes after it
                             // (numerically, 0x01 == 0x0001 == 0x000001)
                             // if (opcode == OP_NOTEQUAL)
                             //    fEqual = !fEqual;
                             popstack(stack);
                             popstack(stack);
                             stack.push_back(fEqual ? vchTrue : vchFalse);
                             if (opcode == OP_EQUALVERIFY) {
                                 if (fEqual) {
                                     popstack(stack);
                                 } else {
                                     return set_error(serror,
                                                      ScriptError::EQUALVERIFY);
                                 }
                             }
                         }
                         break;
 
                     //
                     // Numeric
                     //
                     case OP_1ADD:
                     case OP_1SUB:
                     case OP_NEGATE:
                     case OP_ABS:
                     case OP_NOT:
                     case OP_0NOTEQUAL: {
                         // (in -- out)
                         if (stack.size() < 1) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         CScriptNum bn(stacktop(-1), fRequireMinimal);
                         switch (opcode) {
                             case OP_1ADD:
                                 bn += bnOne;
                                 break;
                             case OP_1SUB:
                                 bn -= bnOne;
                                 break;
                             case OP_NEGATE:
                                 bn = -bn;
                                 break;
                             case OP_ABS:
                                 if (bn < bnZero) {
                                     bn = -bn;
                                 }
                                 break;
                             case OP_NOT:
                                 bn = (bn == bnZero);
                                 break;
                             case OP_0NOTEQUAL:
                                 bn = (bn != bnZero);
                                 break;
                             default:
                                 assert(!"invalid opcode");
                                 break;
                         }
                         popstack(stack);
                         stack.push_back(bn.getvch());
                     } break;
 
                     case OP_ADD:
                     case OP_SUB:
                     case OP_DIV:
                     case OP_MOD:
                     case OP_BOOLAND:
                     case OP_BOOLOR:
                     case OP_NUMEQUAL:
                     case OP_NUMEQUALVERIFY:
                     case OP_NUMNOTEQUAL:
                     case OP_LESSTHAN:
                     case OP_GREATERTHAN:
                     case OP_LESSTHANOREQUAL:
                     case OP_GREATERTHANOREQUAL:
                     case OP_MIN:
                     case OP_MAX: {
                         // (x1 x2 -- out)
                         if (stack.size() < 2) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         CScriptNum bn1(stacktop(-2), fRequireMinimal);
                         CScriptNum bn2(stacktop(-1), fRequireMinimal);
                         CScriptNum bn(0);
                         switch (opcode) {
                             case OP_ADD:
                                 bn = bn1 + bn2;
                                 break;
 
                             case OP_SUB:
                                 bn = bn1 - bn2;
                                 break;
 
                             case OP_DIV:
                                 // denominator must not be 0
                                 if (bn2 == 0) {
                                     return set_error(serror,
                                                      ScriptError::DIV_BY_ZERO);
                                 }
                                 bn = bn1 / bn2;
                                 break;
 
                             case OP_MOD:
                                 // divisor must not be 0
                                 if (bn2 == 0) {
                                     return set_error(serror,
                                                      ScriptError::MOD_BY_ZERO);
                                 }
                                 bn = bn1 % bn2;
                                 break;
 
                             case OP_BOOLAND:
                                 bn = (bn1 != bnZero && bn2 != bnZero);
                                 break;
                             case OP_BOOLOR:
                                 bn = (bn1 != bnZero || bn2 != bnZero);
                                 break;
                             case OP_NUMEQUAL:
                                 bn = (bn1 == bn2);
                                 break;
                             case OP_NUMEQUALVERIFY:
                                 bn = (bn1 == bn2);
                                 break;
                             case OP_NUMNOTEQUAL:
                                 bn = (bn1 != bn2);
                                 break;
                             case OP_LESSTHAN:
                                 bn = (bn1 < bn2);
                                 break;
                             case OP_GREATERTHAN:
                                 bn = (bn1 > bn2);
                                 break;
                             case OP_LESSTHANOREQUAL:
                                 bn = (bn1 <= bn2);
                                 break;
                             case OP_GREATERTHANOREQUAL:
                                 bn = (bn1 >= bn2);
                                 break;
                             case OP_MIN:
                                 bn = (bn1 < bn2 ? bn1 : bn2);
                                 break;
                             case OP_MAX:
                                 bn = (bn1 > bn2 ? bn1 : bn2);
                                 break;
                             default:
                                 assert(!"invalid opcode");
                                 break;
                         }
                         popstack(stack);
                         popstack(stack);
                         stack.push_back(bn.getvch());
 
                         if (opcode == OP_NUMEQUALVERIFY) {
                             if (CastToBool(stacktop(-1))) {
                                 popstack(stack);
                             } else {
                                 return set_error(serror,
                                                  ScriptError::NUMEQUALVERIFY);
                             }
                         }
                     } break;
 
                     case OP_WITHIN: {
                         // (x min max -- out)
                         if (stack.size() < 3) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         CScriptNum bn1(stacktop(-3), fRequireMinimal);
                         CScriptNum bn2(stacktop(-2), fRequireMinimal);
                         CScriptNum bn3(stacktop(-1), fRequireMinimal);
                         bool fValue = (bn2 <= bn1 && bn1 < bn3);
                         popstack(stack);
                         popstack(stack);
                         popstack(stack);
                         stack.push_back(fValue ? vchTrue : vchFalse);
                     } break;
 
                     //
                     // Crypto
                     //
                     case OP_RIPEMD160:
                     case OP_SHA1:
                     case OP_SHA256:
                     case OP_HASH160:
                     case OP_HASH256: {
                         // (in -- hash)
                         if (stack.size() < 1) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         valtype &vch = stacktop(-1);
                         valtype vchHash((opcode == OP_RIPEMD160 ||
                                          opcode == OP_SHA1 ||
                                          opcode == OP_HASH160)
                                             ? 20
                                             : 32);
                         if (opcode == OP_RIPEMD160) {
                             CRIPEMD160()
                                 .Write(vch.data(), vch.size())
                                 .Finalize(vchHash.data());
                         } else if (opcode == OP_SHA1) {
                             CSHA1()
                                 .Write(vch.data(), vch.size())
                                 .Finalize(vchHash.data());
                         } else if (opcode == OP_SHA256) {
                             CSHA256()
                                 .Write(vch.data(), vch.size())
                                 .Finalize(vchHash.data());
                         } else if (opcode == OP_HASH160) {
                             CHash160()
                                 .Write(vch.data(), vch.size())
                                 .Finalize(vchHash.data());
                         } else if (opcode == OP_HASH256) {
                             CHash256()
                                 .Write(vch.data(), vch.size())
                                 .Finalize(vchHash.data());
                         }
                         popstack(stack);
                         stack.push_back(vchHash);
                     } break;
 
                     case OP_CODESEPARATOR: {
                         // Hash starts after the code separator
                         pbegincodehash = pc;
                     } break;
 
                     case OP_CHECKSIG:
                     case OP_CHECKSIGVERIFY: {
                         // (sig pubkey -- bool)
                         if (stack.size() < 2) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         valtype &vchSig = stacktop(-2);
                         valtype &vchPubKey = stacktop(-1);
 
                         if (!CheckTransactionSignatureEncoding(vchSig, flags,
                                                                serror) ||
                             !CheckPubKeyEncoding(vchPubKey, flags, serror)) {
                             // serror is set
                             return false;
                         }
 
                         // Subset of script starting at the most recent
                         // codeseparator
                         CScript scriptCode(pbegincodehash, pend);
 
                         // Remove signature for pre-fork scripts
                         CleanupScriptCode(scriptCode, vchSig, flags);
 
                         bool fSuccess = checker.CheckSig(vchSig, vchPubKey,
                                                          scriptCode, flags);
 
                         if (!fSuccess && (flags & SCRIPT_VERIFY_NULLFAIL) &&
                             vchSig.size()) {
                             return set_error(serror, ScriptError::SIG_NULLFAIL);
                         }
 
                         popstack(stack);
                         popstack(stack);
                         stack.push_back(fSuccess ? vchTrue : vchFalse);
                         if (opcode == OP_CHECKSIGVERIFY) {
                             if (fSuccess) {
                                 popstack(stack);
                             } else {
                                 return set_error(serror,
                                                  ScriptError::CHECKSIGVERIFY);
                             }
                         }
                     } break;
 
                     case OP_CHECKDATASIG:
                     case OP_CHECKDATASIGVERIFY: {
                         // (sig message pubkey -- bool)
                         if (stack.size() < 3) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
 
                         valtype &vchSig = stacktop(-3);
                         valtype &vchMessage = stacktop(-2);
                         valtype &vchPubKey = stacktop(-1);
 
                         if (!CheckDataSignatureEncoding(vchSig, flags,
                                                         serror) ||
                             !CheckPubKeyEncoding(vchPubKey, flags, serror)) {
                             // serror is set
                             return false;
                         }
 
                         bool fSuccess = false;
                         if (vchSig.size()) {
                             valtype vchHash(32);
                             CSHA256()
                                 .Write(vchMessage.data(), vchMessage.size())
                                 .Finalize(vchHash.data());
                             fSuccess = checker.VerifySignature(
                                 vchSig, CPubKey(vchPubKey), uint256(vchHash));
                         }
 
                         if (!fSuccess && (flags & SCRIPT_VERIFY_NULLFAIL) &&
                             vchSig.size()) {
                             return set_error(serror, ScriptError::SIG_NULLFAIL);
                         }
 
                         popstack(stack);
                         popstack(stack);
                         popstack(stack);
                         stack.push_back(fSuccess ? vchTrue : vchFalse);
                         if (opcode == OP_CHECKDATASIGVERIFY) {
                             if (fSuccess) {
                                 popstack(stack);
                             } else {
                                 return set_error(
                                     serror, ScriptError::CHECKDATASIGVERIFY);
                             }
                         }
                     } break;
 
                     case OP_CHECKMULTISIG:
                     case OP_CHECKMULTISIGVERIFY: {
                         // ([dummy] [sig ...] num_of_signatures [pubkey ...]
                         // num_of_pubkeys -- bool)
                         const size_t idxKeyCount = 1;
                         if (stack.size() < idxKeyCount) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         const int nKeysCount =
                             CScriptNum(stacktop(-idxKeyCount), fRequireMinimal)
                                 .getint();
                         if (nKeysCount < 0 ||
                             nKeysCount > MAX_PUBKEYS_PER_MULTISIG) {
                             return set_error(serror, ScriptError::PUBKEY_COUNT);
                         }
                         nOpCount += nKeysCount;
                         if (nOpCount > MAX_OPS_PER_SCRIPT) {
                             return set_error(serror, ScriptError::OP_COUNT);
                         }
 
                         // stack depth of the top pubkey
                         const size_t idxTopKey = idxKeyCount + 1;
 
                         // stack depth of nSigsCount
                         const size_t idxSigCount = idxTopKey + nKeysCount;
                         if (stack.size() < idxSigCount) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         const int nSigsCount =
                             CScriptNum(stacktop(-idxSigCount), fRequireMinimal)
                                 .getint();
                         if (nSigsCount < 0 || nSigsCount > nKeysCount) {
                             return set_error(serror, ScriptError::SIG_COUNT);
                         }
 
                         // stack depth of the top signature
                         const size_t idxTopSig = idxSigCount + 1;
 
                         // stack depth of the dummy element
                         const size_t idxDummy = idxTopSig + nSigsCount;
                         if (stack.size() < idxDummy) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
 
                         // A bug causes CHECKMULTISIG to consume one extra
                         // argument whose contents were not checked in any way.
                         //
                         // Unfortunately this is a potential source of
                         // mutability, so optionally verify it is exactly equal
                         // to zero.
                         if ((flags & SCRIPT_VERIFY_NULLDUMMY) &&
                             stacktop(-idxDummy).size()) {
                             return set_error(serror,
                                              ScriptError::SIG_NULLDUMMY);
                         }
 
                         // Subset of script starting at the most recent
                         // codeseparator
                         CScript scriptCode(pbegincodehash, pend);
 
                         // Remove signature for pre-fork scripts
                         for (int k = 0; k < nSigsCount; k++) {
                             valtype &vchSig = stacktop(-idxTopSig - k);
                             CleanupScriptCode(scriptCode, vchSig, flags);
                         }
 
                         bool fSuccess = true;
                         int nSigsRemaining = nSigsCount;
                         int nKeysRemaining = nKeysCount;
                         while (fSuccess && nSigsRemaining > 0) {
                             valtype &vchSig = stacktop(
                                 -idxTopSig - (nSigsCount - nSigsRemaining));
                             valtype &vchPubKey = stacktop(
                                 -idxTopKey - (nKeysCount - nKeysRemaining));
 
                             // Note how this makes the exact order of
                             // pubkey/signature evaluation distinguishable by
                             // CHECKMULTISIG NOT if the STRICTENC flag is set.
                             // See the script_(in)valid tests for details.
                             if (!CheckTransactionECDSASignatureEncoding(
                                     vchSig, flags, serror) ||
                                 !CheckPubKeyEncoding(vchPubKey, flags,
                                                      serror)) {
                                 // serror is set
                                 return false;
                             }
 
                             // Check signature
                             bool fOk = checker.CheckSig(vchSig, vchPubKey,
                                                         scriptCode, flags);
 
                             if (fOk) {
                                 nSigsRemaining--;
                             }
                             nKeysRemaining--;
 
                             // If there are more signatures left than keys left,
                             // then too many signatures have failed. Exit early,
                             // without checking any further signatures.
                             if (nSigsRemaining > nKeysRemaining) {
                                 fSuccess = false;
                             }
                         }
 
                         // If the operation failed, we require that all
                         // signatures must be empty vector
                         if (!fSuccess && (flags & SCRIPT_VERIFY_NULLFAIL)) {
                             for (int i = 0; i < nSigsCount; i++) {
                                 if (stacktop(-idxTopSig - i).size()) {
                                     return set_error(serror,
                                                      ScriptError::SIG_NULLFAIL);
                                 }
                             }
                         }
 
                         // Clean up stack of all arguments
                         for (size_t i = 0; i < idxDummy; i++) {
                             popstack(stack);
                         }
 
                         stack.push_back(fSuccess ? vchTrue : vchFalse);
                         if (opcode == OP_CHECKMULTISIGVERIFY) {
                             if (fSuccess) {
                                 popstack(stack);
                             } else {
                                 return set_error(
                                     serror, ScriptError::CHECKMULTISIGVERIFY);
                             }
                         }
                     } break;
 
                     //
                     // Byte string operations
                     //
                     case OP_CAT: {
                         // (x1 x2 -- out)
                         if (stack.size() < 2) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
                         valtype &vch1 = stacktop(-2);
                         valtype &vch2 = stacktop(-1);
                         if (vch1.size() + vch2.size() >
                             MAX_SCRIPT_ELEMENT_SIZE) {
                             return set_error(serror, ScriptError::PUSH_SIZE);
                         }
                         vch1.insert(vch1.end(), vch2.begin(), vch2.end());
                         popstack(stack);
                     } break;
 
                     case OP_SPLIT: {
                         // (in position -- x1 x2)
                         if (stack.size() < 2) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
 
                         const valtype &data = stacktop(-2);
 
                         // Make sure the split point is appropriate.
                         uint64_t position =
                             CScriptNum(stacktop(-1), fRequireMinimal).getint();
                         if (position > data.size()) {
                             return set_error(serror,
                                              ScriptError::INVALID_SPLIT_RANGE);
                         }
 
                         // Prepare the results in their own buffer as `data`
                         // will be invalidated.
                         valtype n1(data.begin(), data.begin() + position);
                         valtype n2(data.begin() + position, data.end());
 
                         // Replace existing stack values by the new values.
                         stacktop(-2) = std::move(n1);
                         stacktop(-1) = std::move(n2);
                     } break;
 
                     //
                     // Conversion operations
                     //
                     case OP_NUM2BIN: {
                         // (in size -- out)
                         if (stack.size() < 2) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
 
                         uint64_t size =
                             CScriptNum(stacktop(-1), fRequireMinimal).getint();
                         if (size > MAX_SCRIPT_ELEMENT_SIZE) {
                             return set_error(serror, ScriptError::PUSH_SIZE);
                         }
 
                         popstack(stack);
                         valtype &rawnum = stacktop(-1);
 
                         // Try to see if we can fit that number in the number of
                         // byte requested.
                         CScriptNum::MinimallyEncode(rawnum);
                         if (rawnum.size() > size) {
                             // We definitively cannot.
                             return set_error(serror,
                                              ScriptError::IMPOSSIBLE_ENCODING);
                         }
 
                         // We already have an element of the right size, we
                         // don't need to do anything.
                         if (rawnum.size() == size) {
                             break;
                         }
 
                         uint8_t signbit = 0x00;
                         if (rawnum.size() > 0) {
                             signbit = rawnum.back() & 0x80;
                             rawnum[rawnum.size() - 1] &= 0x7f;
                         }
 
                         rawnum.reserve(size);
                         while (rawnum.size() < size - 1) {
                             rawnum.push_back(0x00);
                         }
 
                         rawnum.push_back(signbit);
                     } break;
 
                     case OP_BIN2NUM: {
                         // (in -- out)
                         if (stack.size() < 1) {
                             return set_error(
                                 serror, ScriptError::INVALID_STACK_OPERATION);
                         }
 
                         valtype &n = stacktop(-1);
                         CScriptNum::MinimallyEncode(n);
 
                         // The resulting number must be a valid number.
                         if (!CScriptNum::IsMinimallyEncoded(n)) {
                             return set_error(serror,
                                              ScriptError::INVALID_NUMBER_RANGE);
                         }
                     } break;
 
                     default:
                         return set_error(serror, ScriptError::BAD_OPCODE);
                 }
             }
 
             // Size limits
             if (stack.size() + altstack.size() > MAX_STACK_SIZE) {
                 return set_error(serror, ScriptError::STACK_SIZE);
             }
         }
     } catch (...) {
         return set_error(serror, ScriptError::UNKNOWN);
     }
 
     if (!vfExec.empty()) {
         return set_error(serror, ScriptError::UNBALANCED_CONDITIONAL);
     }
 
     return set_success(serror);
 }
 
 namespace {
 
 /**
  * Wrapper that serializes like CTransaction, but with the modifications
  *  required for the signature hash done in-place
  */
 class CTransactionSignatureSerializer {
 private:
     //!< reference to the spending transaction (the one being serialized)
     const CTransaction &txTo;
     //!< output script being consumed
     const CScript &scriptCode;
     //!< input index of txTo being signed
     const unsigned int nIn;
     //!< container for hashtype flags
     const SigHashType sigHashType;
 
 public:
     CTransactionSignatureSerializer(const CTransaction &txToIn,
                                     const CScript &scriptCodeIn,
                                     unsigned int nInIn,
                                     SigHashType sigHashTypeIn)
         : txTo(txToIn), scriptCode(scriptCodeIn), nIn(nInIn),
           sigHashType(sigHashTypeIn) {}
 
     /** Serialize the passed scriptCode, skipping OP_CODESEPARATORs */
     template <typename S> void SerializeScriptCode(S &s) const {
         CScript::const_iterator it = scriptCode.begin();
         CScript::const_iterator itBegin = it;
         opcodetype opcode;
         unsigned int nCodeSeparators = 0;
         while (scriptCode.GetOp(it, opcode)) {
             if (opcode == OP_CODESEPARATOR) {
                 nCodeSeparators++;
             }
         }
         ::WriteCompactSize(s, scriptCode.size() - nCodeSeparators);
         it = itBegin;
         while (scriptCode.GetOp(it, opcode)) {
             if (opcode == OP_CODESEPARATOR) {
                 s.write((char *)&itBegin[0], it - itBegin - 1);
                 itBegin = it;
             }
         }
         if (itBegin != scriptCode.end()) {
             s.write((char *)&itBegin[0], it - itBegin);
         }
     }
 
     /** Serialize an input of txTo */
     template <typename S> void SerializeInput(S &s, unsigned int nInput) const {
         // In case of SIGHASH_ANYONECANPAY, only the input being signed is
         // serialized
         if (sigHashType.hasAnyoneCanPay()) {
             nInput = nIn;
         }
         // Serialize the prevout
         ::Serialize(s, txTo.vin[nInput].prevout);
         // Serialize the script
         if (nInput != nIn) {
             // Blank out other inputs' signatures
             ::Serialize(s, CScript());
         } else {
             SerializeScriptCode(s);
         }
         // Serialize the nSequence
         if (nInput != nIn &&
             (sigHashType.getBaseType() == BaseSigHashType::SINGLE ||
              sigHashType.getBaseType() == BaseSigHashType::NONE)) {
             // let the others update at will
             ::Serialize(s, (int)0);
         } else {
             ::Serialize(s, txTo.vin[nInput].nSequence);
         }
     }
 
     /** Serialize an output of txTo */
     template <typename S>
     void SerializeOutput(S &s, unsigned int nOutput) const {
         if (sigHashType.getBaseType() == BaseSigHashType::SINGLE &&
             nOutput != nIn) {
             // Do not lock-in the txout payee at other indices as txin
             ::Serialize(s, CTxOut());
         } else {
             ::Serialize(s, txTo.vout[nOutput]);
         }
     }
 
     /** Serialize txTo */
     template <typename S> void Serialize(S &s) const {
         // Serialize nVersion
         ::Serialize(s, txTo.nVersion);
         // Serialize vin
         unsigned int nInputs =
             sigHashType.hasAnyoneCanPay() ? 1 : txTo.vin.size();
         ::WriteCompactSize(s, nInputs);
         for (unsigned int nInput = 0; nInput < nInputs; nInput++) {
             SerializeInput(s, nInput);
         }
         // Serialize vout
         unsigned int nOutputs =
             (sigHashType.getBaseType() == BaseSigHashType::NONE)
                 ? 0
                 : ((sigHashType.getBaseType() == BaseSigHashType::SINGLE)
                        ? nIn + 1
                        : txTo.vout.size());
         ::WriteCompactSize(s, nOutputs);
         for (unsigned int nOutput = 0; nOutput < nOutputs; nOutput++) {
             SerializeOutput(s, nOutput);
         }
         // Serialize nLockTime
         ::Serialize(s, txTo.nLockTime);
     }
 };
 
 uint256 GetPrevoutHash(const CTransaction &txTo) {
     CHashWriter ss(SER_GETHASH, 0);
     for (const auto &txin : txTo.vin) {
         ss << txin.prevout;
     }
     return ss.GetHash();
 }
 
 uint256 GetSequenceHash(const CTransaction &txTo) {
     CHashWriter ss(SER_GETHASH, 0);
     for (const auto &txin : txTo.vin) {
         ss << txin.nSequence;
     }
     return ss.GetHash();
 }
 
 uint256 GetOutputsHash(const CTransaction &txTo) {
     CHashWriter ss(SER_GETHASH, 0);
     for (const auto &txout : txTo.vout) {
         ss << txout;
     }
     return ss.GetHash();
 }
 
 } // namespace
 
 PrecomputedTransactionData::PrecomputedTransactionData(
     const CTransaction &txTo) {
     hashPrevouts = GetPrevoutHash(txTo);
     hashSequence = GetSequenceHash(txTo);
     hashOutputs = GetOutputsHash(txTo);
 }
 
 uint256 SignatureHash(const CScript &scriptCode, const CTransaction &txTo,
                       unsigned int nIn, SigHashType sigHashType,
                       const Amount amount,
                       const PrecomputedTransactionData *cache, uint32_t flags) {
     if (flags & SCRIPT_ENABLE_REPLAY_PROTECTION) {
         // Legacy chain's value for fork id must be of the form 0xffxxxx.
         // By xoring with 0xdead, we ensure that the value will be different
         // from the original one, even if it already starts with 0xff.
         uint32_t newForkValue = sigHashType.getForkValue() ^ 0xdead;
         sigHashType = sigHashType.withForkValue(0xff0000 | newForkValue);
     }
 
     if (sigHashType.hasForkId() && (flags & SCRIPT_ENABLE_SIGHASH_FORKID)) {
         uint256 hashPrevouts;
         uint256 hashSequence;
         uint256 hashOutputs;
 
         if (!sigHashType.hasAnyoneCanPay()) {
             hashPrevouts = cache ? cache->hashPrevouts : GetPrevoutHash(txTo);
         }
 
         if (!sigHashType.hasAnyoneCanPay() &&
             (sigHashType.getBaseType() != BaseSigHashType::SINGLE) &&
             (sigHashType.getBaseType() != BaseSigHashType::NONE)) {
             hashSequence = cache ? cache->hashSequence : GetSequenceHash(txTo);
         }
 
         if ((sigHashType.getBaseType() != BaseSigHashType::SINGLE) &&
             (sigHashType.getBaseType() != BaseSigHashType::NONE)) {
             hashOutputs = cache ? cache->hashOutputs : GetOutputsHash(txTo);
         } else if ((sigHashType.getBaseType() == BaseSigHashType::SINGLE) &&
                    (nIn < txTo.vout.size())) {
             CHashWriter ss(SER_GETHASH, 0);
             ss << txTo.vout[nIn];
             hashOutputs = ss.GetHash();
         }
 
         CHashWriter ss(SER_GETHASH, 0);
         // Version
         ss << txTo.nVersion;
         // Input prevouts/nSequence (none/all, depending on flags)
         ss << hashPrevouts;
         ss << hashSequence;
         // The input being signed (replacing the scriptSig with scriptCode +
         // amount). The prevout may already be contained in hashPrevout, and the
         // nSequence may already be contain in hashSequence.
         ss << txTo.vin[nIn].prevout;
         ss << scriptCode;
         ss << amount;
         ss << txTo.vin[nIn].nSequence;
         // Outputs (none/one/all, depending on flags)
         ss << hashOutputs;
         // Locktime
         ss << txTo.nLockTime;
         // Sighash type
         ss << sigHashType;
 
         return ss.GetHash();
     }
 
     static const uint256 one(uint256S(
         "0000000000000000000000000000000000000000000000000000000000000001"));
     if (nIn >= txTo.vin.size()) {
         //  nIn out of range
         return one;
     }
 
     // Check for invalid use of SIGHASH_SINGLE
     if ((sigHashType.getBaseType() == BaseSigHashType::SINGLE) &&
         (nIn >= txTo.vout.size())) {
         //  nOut out of range
         return one;
     }
 
     // Wrapper to serialize only the necessary parts of the transaction being
     // signed
     CTransactionSignatureSerializer txTmp(txTo, scriptCode, nIn, sigHashType);
 
     // Serialize and hash
     CHashWriter ss(SER_GETHASH, 0);
     ss << txTmp << sigHashType;
     return ss.GetHash();
 }
 
 bool BaseSignatureChecker::VerifySignature(const std::vector<uint8_t> &vchSig,
                                            const CPubKey &pubkey,
                                            const uint256 &sighash) const {
     if (vchSig.size() == 64) {
         return pubkey.VerifySchnorr(sighash, vchSig);
     } else {
         return pubkey.VerifyECDSA(sighash, vchSig);
     }
 }
 
 bool TransactionSignatureChecker::CheckSig(
     const std::vector<uint8_t> &vchSigIn, const std::vector<uint8_t> &vchPubKey,
     const CScript &scriptCode, uint32_t flags) const {
     CPubKey pubkey(vchPubKey);
     if (!pubkey.IsValid()) {
         return false;
     }
 
     // Hash type is one byte tacked on to the end of the signature
     std::vector<uint8_t> vchSig(vchSigIn);
     if (vchSig.empty()) {
         return false;
     }
     SigHashType sigHashType = GetHashType(vchSig);
     vchSig.pop_back();
 
     uint256 sighash = SignatureHash(scriptCode, *txTo, nIn, sigHashType, amount,
                                     this->txdata, flags);
 
     if (!VerifySignature(vchSig, pubkey, sighash)) {
         return false;
     }
 
     return true;
 }
 
 bool TransactionSignatureChecker::CheckLockTime(
     const CScriptNum &nLockTime) const {
     // There are two kinds of nLockTime: lock-by-blockheight and
     // lock-by-blocktime, distinguished by whether nLockTime <
     // LOCKTIME_THRESHOLD.
     //
     // We want to compare apples to apples, so fail the script unless the type
     // of nLockTime being tested is the same as the nLockTime in the
     // transaction.
     if (!((txTo->nLockTime < LOCKTIME_THRESHOLD &&
            nLockTime < LOCKTIME_THRESHOLD) ||
           (txTo->nLockTime >= LOCKTIME_THRESHOLD &&
            nLockTime >= LOCKTIME_THRESHOLD))) {
         return false;
     }
 
     // Now that we know we're comparing apples-to-apples, the comparison is a
     // simple numeric one.
     if (nLockTime > int64_t(txTo->nLockTime)) {
         return false;
     }
 
     // Finally the nLockTime feature can be disabled and thus
     // CHECKLOCKTIMEVERIFY bypassed if every txin has been finalized by setting
     // nSequence to maxint. The transaction would be allowed into the
     // blockchain, making the opcode ineffective.
     //
     // Testing if this vin is not final is sufficient to prevent this condition.
     // Alternatively we could test all inputs, but testing just this input
     // minimizes the data required to prove correct CHECKLOCKTIMEVERIFY
     // execution.
     if (CTxIn::SEQUENCE_FINAL == txTo->vin[nIn].nSequence) {
         return false;
     }
 
     return true;
 }
 
 bool TransactionSignatureChecker::CheckSequence(
     const CScriptNum &nSequence) const {
     // Relative lock times are supported by comparing the passed in operand to
     // the sequence number of the input.
     const int64_t txToSequence = int64_t(txTo->vin[nIn].nSequence);
 
     // Fail if the transaction's version number is not set high enough to
     // trigger BIP 68 rules.
     if (static_cast<uint32_t>(txTo->nVersion) < 2) {
         return false;
     }
 
     // Sequence numbers with their most significant bit set are not consensus
     // constrained. Testing that the transaction's sequence number do not have
     // this bit set prevents using this property to get around a
     // CHECKSEQUENCEVERIFY check.
     if (txToSequence & CTxIn::SEQUENCE_LOCKTIME_DISABLE_FLAG) {
         return false;
     }
 
     // Mask off any bits that do not have consensus-enforced meaning before
     // doing the integer comparisons
     const uint32_t nLockTimeMask =
         CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG | CTxIn::SEQUENCE_LOCKTIME_MASK;
     const int64_t txToSequenceMasked = txToSequence & nLockTimeMask;
     const CScriptNum nSequenceMasked = nSequence & nLockTimeMask;
 
     // There are two kinds of nSequence: lock-by-blockheight and
     // lock-by-blocktime, distinguished by whether nSequenceMasked <
     // CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG.
     //
     // We want to compare apples to apples, so fail the script unless the type
     // of nSequenceMasked being tested is the same as the nSequenceMasked in the
     // transaction.
     if (!((txToSequenceMasked < CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG &&
            nSequenceMasked < CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG) ||
           (txToSequenceMasked >= CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG &&
            nSequenceMasked >= CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG))) {
         return false;
     }
 
     // Now that we know we're comparing apples-to-apples, the comparison is a
     // simple numeric one.
     if (nSequenceMasked > txToSequenceMasked) {
         return false;
     }
 
     return true;
 }
 
 bool VerifyScript(const CScript &scriptSig, const CScript &scriptPubKey,
                   uint32_t flags, const BaseSignatureChecker &checker,
                   ScriptError *serror) {
     set_error(serror, ScriptError::UNKNOWN);
 
     // If FORKID is enabled, we also ensure strict encoding.
     if (flags & SCRIPT_ENABLE_SIGHASH_FORKID) {
         flags |= SCRIPT_VERIFY_STRICTENC;
     }
 
     if ((flags & SCRIPT_VERIFY_SIGPUSHONLY) != 0 && !scriptSig.IsPushOnly()) {
         return set_error(serror, ScriptError::SIG_PUSHONLY);
     }
 
     std::vector<valtype> stack, stackCopy;
     if (!EvalScript(stack, scriptSig, flags, checker, serror)) {
         // serror is set
         return false;
     }
     if (flags & SCRIPT_VERIFY_P2SH) {
         stackCopy = stack;
     }
     if (!EvalScript(stack, scriptPubKey, flags, checker, serror)) {
         // serror is set
         return false;
     }
     if (stack.empty()) {
         return set_error(serror, ScriptError::EVAL_FALSE);
     }
     if (CastToBool(stack.back()) == false) {
         return set_error(serror, ScriptError::EVAL_FALSE);
     }
 
     // Additional validation for spend-to-script-hash transactions:
     if ((flags & SCRIPT_VERIFY_P2SH) && scriptPubKey.IsPayToScriptHash()) {
         // scriptSig must be literals-only or validation fails
         if (!scriptSig.IsPushOnly()) {
             return set_error(serror, ScriptError::SIG_PUSHONLY);
         }
 
         // Restore stack.
         swap(stack, stackCopy);
 
         // stack cannot be empty here, because if it was the P2SH  HASH <> EQUAL
         // scriptPubKey would be evaluated with an empty stack and the
         // EvalScript above would return false.
         assert(!stack.empty());
 
         const valtype &pubKeySerialized = stack.back();
         CScript pubKey2(pubKeySerialized.begin(), pubKeySerialized.end());
         popstack(stack);
 
         // Bail out early if SCRIPT_DISALLOW_SEGWIT_RECOVERY is not set, the
         // redeem script is a p2sh segwit program, and it was the only item
         // pushed onto the stack.
         if ((flags & SCRIPT_DISALLOW_SEGWIT_RECOVERY) == 0 && stack.empty() &&
             pubKey2.IsWitnessProgram()) {
             return set_success(serror);
         }
 
         if (!EvalScript(stack, pubKey2, flags, checker, serror)) {
             // serror is set
             return false;
         }
         if (stack.empty()) {
             return set_error(serror, ScriptError::EVAL_FALSE);
         }
         if (!CastToBool(stack.back())) {
             return set_error(serror, ScriptError::EVAL_FALSE);
         }
     }
 
     // The CLEANSTACK check is only performed after potential P2SH evaluation,
     // as the non-P2SH evaluation of a P2SH script will obviously not result in
     // a clean stack (the P2SH inputs remain). The same holds for witness
     // evaluation.
     if ((flags & SCRIPT_VERIFY_CLEANSTACK) != 0) {
         // Disallow CLEANSTACK without P2SH, as otherwise a switch
         // CLEANSTACK->P2SH+CLEANSTACK would be possible, which is not a
         // softfork (and P2SH should be one).
         assert((flags & SCRIPT_VERIFY_P2SH) != 0);
         if (stack.size() != 1) {
             return set_error(serror, ScriptError::CLEANSTACK);
         }
     }
 
     return set_success(serror);
 }