Novacoin/ScriptCode.cs

   1 /**
   2  *  Novacoin classes library
   3  *  Copyright (C) 2015 Alex D. (balthazar.ad@gmail.com)
   4
   5  *  This program is free software: you can redistribute it and/or modify
   6  *  it under the terms of the GNU Affero General Public License as
   7  *  published by the Free Software Foundation, either version 3 of the
   8  *  License, or (at your option) any later version.
   9
  10  *  This program is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  *  GNU Affero General Public License for more details.
  14
  15  *  You should have received a copy of the GNU Affero General Public License
  16  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17  */
  18
  19 using System;
  20 using System.Collections.Generic;
  21 using System.Linq;
  22 using System.Numerics;
  23 using System.Text;
  24
  25 namespace Novacoin
  26 {
  27     /// <summary>
  28     /// Script instructions
  29     /// </summary>
  30     public enum instruction
  31     {
  32         // push value
  33         OP_0 = 0x00,
  34         OP_FALSE = OP_0,
  35         OP_PUSHDATA1 = 0x4c,
  36         OP_PUSHDATA2 = 0x4d,
  37         OP_PUSHDATA4 = 0x4e,
  38         OP_1NEGATE = 0x4f,
  39         OP_RESERVED = 0x50,
  40         OP_1 = 0x51,
  41         OP_TRUE = OP_1,
  42         OP_2 = 0x52,
  43         OP_3 = 0x53,
  44         OP_4 = 0x54,
  45         OP_5 = 0x55,
  46         OP_6 = 0x56,
  47         OP_7 = 0x57,
  48         OP_8 = 0x58,
  49         OP_9 = 0x59,
  50         OP_10 = 0x5a,
  51         OP_11 = 0x5b,
  52         OP_12 = 0x5c,
  53         OP_13 = 0x5d,
  54         OP_14 = 0x5e,
  55         OP_15 = 0x5f,
  56         OP_16 = 0x60,
  57
  58         // control
  59         OP_NOP = 0x61,
  60         OP_VER = 0x62,
  61         OP_IF = 0x63,
  62         OP_NOTIF = 0x64,
  63         OP_VERIF = 0x65,
  64         OP_VERNOTIF = 0x66,
  65         OP_ELSE = 0x67,
  66         OP_ENDIF = 0x68,
  67         OP_VERIFY = 0x69,
  68         OP_RETURN = 0x6a,
  69
  70         // stack ops
  71         OP_TOALTSTACK = 0x6b,
  72         OP_FROMALTSTACK = 0x6c,
  73         OP_2DROP = 0x6d,
  74         OP_2DUP = 0x6e,
  75         OP_3DUP = 0x6f,
  76         OP_2OVER = 0x70,
  77         OP_2ROT = 0x71,
  78         OP_2SWAP = 0x72,
  79         OP_IFDUP = 0x73,
  80         OP_DEPTH = 0x74,
  81         OP_DROP = 0x75,
  82         OP_DUP = 0x76,
  83         OP_NIP = 0x77,
  84         OP_OVER = 0x78,
  85         OP_PICK = 0x79,
  86         OP_ROLL = 0x7a,
  87         OP_ROT = 0x7b,
  88         OP_SWAP = 0x7c,
  89         OP_TUCK = 0x7d,
  90
  91         // splice ops
  92         OP_CAT = 0x7e,
  93         OP_SUBSTR = 0x7f,
  94         OP_LEFT = 0x80,
  95         OP_RIGHT = 0x81,
  96         OP_SIZE = 0x82,
  97
  98         // bit logic
  99         OP_INVERT = 0x83,
 100         OP_AND = 0x84,
 101         OP_OR = 0x85,
 102         OP_XOR = 0x86,
 103         OP_EQUAL = 0x87,
 104         OP_EQUALVERIFY = 0x88,
 105         OP_RESERVED1 = 0x89,
 106         OP_RESERVED2 = 0x8a,
 107
 108         // numeric
 109         OP_1ADD = 0x8b,
 110         OP_1SUB = 0x8c,
 111         OP_2MUL = 0x8d,
 112         OP_2DIV = 0x8e,
 113         OP_NEGATE = 0x8f,
 114         OP_ABS = 0x90,
 115         OP_NOT = 0x91,
 116         OP_0NOTEQUAL = 0x92,
 117
 118         OP_ADD = 0x93,
 119         OP_SUB = 0x94,
 120         OP_MUL = 0x95,
 121         OP_DIV = 0x96,
 122         OP_MOD = 0x97,
 123         OP_LSHIFT = 0x98,
 124         OP_RSHIFT = 0x99,
 125
 126         OP_BOOLAND = 0x9a,
 127         OP_BOOLOR = 0x9b,
 128         OP_NUMEQUAL = 0x9c,
 129         OP_NUMEQUALVERIFY = 0x9d,
 130         OP_NUMNOTEQUAL = 0x9e,
 131         OP_LESSTHAN = 0x9f,
 132         OP_GREATERTHAN = 0xa0,
 133         OP_LESSTHANOREQUAL = 0xa1,
 134         OP_GREATERTHANOREQUAL = 0xa2,
 135         OP_MIN = 0xa3,
 136         OP_MAX = 0xa4,
 137
 138         OP_WITHIN = 0xa5,
 139
 140         // crypto
 141         OP_RIPEMD160 = 0xa6,
 142         OP_SHA1 = 0xa7,
 143         OP_SHA256 = 0xa8,
 144         OP_HASH160 = 0xa9,
 145         OP_HASH256 = 0xaa,
 146         OP_CODESEPARATOR = 0xab,
 147         OP_CHECKSIG = 0xac,
 148         OP_CHECKSIGVERIFY = 0xad,
 149         OP_CHECKMULTISIG = 0xae,
 150         OP_CHECKMULTISIGVERIFY = 0xaf,
 151
 152         // expansion
 153         OP_NOP1 = 0xb0,
 154         OP_NOP2 = 0xb1,
 155         OP_NOP3 = 0xb2,
 156         OP_NOP4 = 0xb3,
 157         OP_NOP5 = 0xb4,
 158         OP_NOP6 = 0xb5,
 159         OP_NOP7 = 0xb6,
 160         OP_NOP8 = 0xb7,
 161         OP_NOP9 = 0xb8,
 162         OP_NOP10 = 0xb9,
 163
 164         // template matching params
 165         OP_SMALLDATA = 0xf9,
 166         OP_SMALLINTEGER = 0xfa,
 167         OP_PUBKEYS = 0xfb,
 168         OP_PUBKEYHASH = 0xfd,
 169         OP_PUBKEY = 0xfe,
 170
 171         OP_INVALIDOPCODE = 0xff,
 172     };
 173
 174     /// <summary>
 175     /// Transaction output types.
 176     /// </summary>
 177     public enum txnouttype
 178     {
 179         TX_NONSTANDARD,
 180
 181         // 'standard' transaction types:
 182         TX_PUBKEY,
 183         TX_PUBKEYHASH,
 184         TX_SCRIPTHASH,
 185         TX_MULTISIG,
 186         TX_NULL_DATA,
 187     };
 188
 189     /// <summary>
 190     /// Signature hash types/flags
 191     /// </summary>
 192     public enum sigflag
 193     {
 194         SIGHASH_ALL = 1,
 195         SIGHASH_NONE = 2,
 196         SIGHASH_SINGLE = 3,
 197         SIGHASH_ANYONECANPAY = 0x80,
 198     };
 199
 200     /** Script verification flags */
 201     public enum scriptflag
 202     {
 203         SCRIPT_VERIFY_NONE = 0,
 204         SCRIPT_VERIFY_P2SH = (1 << 0), // evaluate P2SH (BIP16) subscripts
 205         SCRIPT_VERIFY_STRICTENC = (1 << 1), // enforce strict conformance to DER and SEC2 for signatures and pubkeys
 206         SCRIPT_VERIFY_LOW_S = (1 << 2), // enforce low S values in signatures (depends on STRICTENC)
 207         SCRIPT_VERIFY_NOCACHE = (1 << 3), // do not store results in signature cache (but do query it)
 208         SCRIPT_VERIFY_NULLDUMMY = (1 << 4), // verify dummy stack item consumed by CHECKMULTISIG is of zero-length
 209     };
 210
 211     public static class ScriptCode
 212     {
 213         public static string GetTxnOutputType(txnouttype t)
 214         {
 215             switch (t)
 216             {
 217                 case txnouttype.TX_NONSTANDARD: return "nonstandard";
 218                 case txnouttype.TX_PUBKEY: return "pubkey";
 219                 case txnouttype.TX_PUBKEYHASH: return "pubkeyhash";
 220                 case txnouttype.TX_SCRIPTHASH: return "scripthash";
 221                 case txnouttype.TX_MULTISIG: return "multisig";
 222                 case txnouttype.TX_NULL_DATA: return "nulldata";
 223             }
 224             return string.Empty;
 225         }
 226
 227         /// <summary>
 228         /// Get the name of instruction
 229         /// </summary>
 230         /// <param name="opcode">Instruction</param>
 231         /// <returns>Instruction name</returns>
 232         public static string GetOpName(instruction opcode)
 233         {
 234             if (opcode == instruction.OP_0) // OP_0 and OP_FALSE are synonyms
 235                 return "OP_0";
 236             if (opcode == instruction.OP_1) // OP_1 and OP_TRUE are synonyms
 237                 return "OP_1";
 238
 239             return Enum.GetName(typeof(instruction), opcode);
 240         }
 241
 242         /// <summary>
 243         /// Get next instruction from list of bytes and extract push arguments if there are some.
 244         /// </summary>
 245         /// <param name="codeBytes">ByteQueue reference.</param>
 246         /// <param name="opcodeRet">Found instruction.</param>
 247         /// <param name="bytesRet">IEnumerable out param which is used to get the push arguments.</param>
 248         /// <returns>Result of operation</returns>
 249         public static bool GetOp(ref ByteQueue codeBytes, out instruction opcodeRet, out byte[] bytesRet)
 250         {
 251             bytesRet = new byte[0];
 252             opcodeRet = instruction.OP_INVALIDOPCODE;
 253
 254             instruction opcode;
 255
 256             try
 257             {
 258                 // Read instruction
 259                 opcode = (instruction)codeBytes.Get();
 260             }
 261             catch (ByteQueueException)
 262             {
 263                 // No instruction found there
 264                 return false;
 265             }
 266
 267             // Immediate operand
 268             if (opcode <= instruction.OP_PUSHDATA4)
 269             {
 270                 var szBytes = new byte[4] { 0, 0, 0, 0 }; // Zero length
 271                 int nSize = 0;
 272
 273                 try
 274                 {
 275                     if (opcode < instruction.OP_PUSHDATA1)
 276                     {
 277                         // Zero value instructions (OP_0, OP_FALSE)
 278                         nSize = (int) opcode;
 279                     }
 280                     else if (opcode == instruction.OP_PUSHDATA1)
 281                     {
 282                         // The next byte contains the number of bytes to be pushed onto the stack,
 283                         //    i.e. you have something like OP_PUSHDATA1 0x01 [0x5a]
 284                         nSize = codeBytes.Get();
 285                     }
 286                     else if (opcode == instruction.OP_PUSHDATA2)
 287                     {
 288                         // The next two bytes contain the number of bytes to be pushed onto the stack,
 289                         //    i.e. now your operation will seem like this: OP_PUSHDATA2 0x01 0x00 [0x5a]
 290                         nSize = BitConverter.ToInt16(codeBytes.Get(2), 0);
 291                     }
 292                     else if (opcode == instruction.OP_PUSHDATA4)
 293                     {
 294                         // The next four bytes contain the number of bytes to be pushed onto the stack,
 295                         //   OP_PUSHDATA4 0x01 0x00 0x00 0x00 [0x5a]
 296                         nSize = BitConverter.ToInt32(codeBytes.Get(4), 0);
 297                     }
 298                 }
 299                 catch (ByteQueueException)
 300                 {
 301                     // Unable to read operand length
 302                     return false;
 303                 }
 304
 305                 if (nSize > 0)
 306                 {
 307                     // If nSize is greater than zero then there is some data available
 308                     try
 309                     {
 310                         // Read found number of bytes into list of OP_PUSHDATAn arguments.
 311                         bytesRet = codeBytes.Get(nSize);
 312                     }
 313                     catch (ByteQueueException)
 314                     {
 315                         // Unable to read data
 316                         return false;
 317                     }
 318                 }
 319             }
 320
 321             opcodeRet = opcode;
 322
 323             return true;
 324         }
 325
 326         /// <summary>
 327         /// Convert value bytes into readable representation.
 328         ///
 329         /// If list lengh is equal or lesser than 4 bytes then bytes are interpreted as integer value. Otherwise you will get hex representation of supplied data.
 330         /// </summary>
 331         /// <param name="bytes">Collection of value bytes.</param>
 332         /// <returns>Formatted value.</returns>
 333         public static string ValueString(byte[] bytes)
 334         {
 335             var sb = new StringBuilder();
 336
 337             if (bytes.Length <= 4)
 338             {
 339                 sb.Append(new BigInteger(bytes));
 340             }
 341             else
 342             {
 343                 return Interop.ToHex(bytes);
 344             }
 345
 346             return sb.ToString();
 347         }
 348
 349         /// <summary>
 350         /// Convert list of stack items into human readable representation.
 351         /// </summary>
 352         /// <param name="stackList">List of stack items.</param>
 353         /// <returns>Formatted value.</returns>
 354         public static string StackString(IList<byte[]> stackList)
 355         {
 356             var sb = new StringBuilder();
 357             foreach (var bytes in stackList)
 358             {
 359                 sb.Append(ValueString(bytes));
 360             }
 361
 362             return sb.ToString();
 363         }
 364
 365         /// <summary>
 366         /// Decode instruction to integer value
 367         /// </summary>
 368         /// <param name="opcode">Small integer instruction (OP_1_NEGATE and OP_0 - OP_16)</param>
 369         /// <returns>Small integer</returns>
 370         public static int DecodeOP_N(instruction opcode, bool AllowNegate = false)
 371         {
 372             if (AllowNegate && opcode == instruction.OP_1NEGATE)
 373             {
 374                 return -1;
 375             }
 376
 377             if (opcode == instruction.OP_0)
 378             {
 379                 return 0;
 380             }
 381
 382             // Only OP_n instructions are supported, throw exception otherwise.
 383             if (opcode < instruction.OP_1 || opcode > instruction.OP_16)
 384             {
 385                 throw new ArgumentException("Invalid integer instruction.");
 386             }
 387
 388             return (int)opcode - (int)(instruction.OP_1 - 1);
 389         }
 390
 391         /// <summary>
 392         /// Converts integer into instruction
 393         /// </summary>
 394         /// <param name="n">Small integer from the range of -1 up to 16.</param>
 395         /// <returns>Corresponding instruction.</returns>
 396         public static instruction EncodeOP_N(int n, bool allowNegate = false)
 397         {
 398             if (allowNegate && n == -1)
 399             {
 400                 return instruction.OP_1NEGATE;
 401             }
 402
 403             if (n == 0)
 404             {
 405                 return instruction.OP_0;
 406             }
 407
 408             // The n value must be in the range of 0 to 16.
 409             if (n < 0 || n > 16)
 410                 throw new ArgumentException("Invalid integer value.");
 411             return (instruction.OP_1 + n - 1);
 412         }
 413
 414         public static int ScriptSigArgsExpected(txnouttype t, IList<byte[]> solutions)
 415         {
 416             switch (t)
 417             {
 418                 case txnouttype.TX_NONSTANDARD:
 419                     return -1;
 420                 case txnouttype.TX_NULL_DATA:
 421                     return 1;
 422                 case txnouttype.TX_PUBKEY:
 423                     return 1;
 424                 case txnouttype.TX_PUBKEYHASH:
 425                     return 2;
 426                 case txnouttype.TX_MULTISIG:
 427                     if (solutions.Count < 1 || solutions.First().Length < 1)
 428                         return -1;
 429                     return solutions.First()[0] + 1;
 430                 case txnouttype.TX_SCRIPTHASH:
 431                     return 1; // doesn't include args needed by the script
 432             }
 433             return -1;
 434         }
 435
 436         /// <summary>
 437         /// Is it a standart type of scriptPubKey?
 438         /// </summary>
 439         /// <param name="scriptPubKey">CScript instance</param>
 440         /// <param name="whichType">utut type</param>
 441         /// <returns>Checking result</returns>
 442         public static bool IsStandard(CScript scriptPubKey, out txnouttype whichType)
 443         {
 444             IList<byte[]> solutions;
 445
 446             if (!Solver(scriptPubKey, out whichType, out solutions))
 447             {
 448                 // No solutions found
 449                 return false;
 450             }
 451
 452             if (whichType == txnouttype.TX_MULTISIG)
 453             {
 454                 // Additional verification of OP_CHECKMULTISIG arguments
 455                 var m = solutions.First()[0];
 456                 var n = solutions.Last()[0];
 457
 458                 // Support up to x-of-3 multisig txns as standard
 459                 if (n < 1 || n > 3)
 460                 {
 461                     return false;
 462                 }
 463                 if (m < 1 || m > n)
 464                 {
 465                     return false;
 466                 }
 467             }
 468
 469             return whichType != txnouttype.TX_NONSTANDARD;
 470         }
 471
 472         /// <summary>
 473         /// Return public keys or hashes from scriptPubKey, for 'standard' transaction types.
 474         /// </summary>
 475         /// <param name="scriptPubKey">CScript instance</param>
 476         /// <param name="typeRet">Output type</param>
 477         /// <param name="solutions">Set of solutions</param>
 478         /// <returns>Result</returns>
 479         public static bool Solver(CScript scriptPubKey, out txnouttype typeRet, out IList<byte[]> solutions)
 480         {
 481             var scriptBytes = ((byte[])scriptPubKey);
 482
 483             solutions = new List<byte[]>();
 484
 485             // There are shortcuts for pay-to-script-hash and pay-to-pubkey-hash, which are more constrained than the other types.
 486
 487             // It is always OP_HASH160 20 [20 byte hash] OP_EQUAL
 488             if (scriptPubKey.IsPayToScriptHash)
 489             {
 490                 typeRet = txnouttype.TX_SCRIPTHASH;
 491
 492                 // Take 20 bytes with offset of 2 bytes
 493                 var hashBytes = scriptBytes.Skip(2).Take(20);
 494                 solutions.Add(hashBytes.ToArray());
 495
 496                 return true;
 497             }
 498
 499             // It is always OP_DUP OP_HASH160 20 [20 byte hash] OP_EQUALVERIFY OP_CHECKSIG
 500             if (scriptPubKey.IsPayToPubKeyHash)
 501             {
 502                 typeRet = txnouttype.TX_PUBKEYHASH;
 503
 504                 // Take 20 bytes with offset of 3 bytes
 505                 var hashBytes = scriptBytes.Skip(3).Take(20);
 506                 solutions.Add(hashBytes.ToArray());
 507
 508                 return true;
 509             }
 510
 511             var templateTuples = new List<Tuple<txnouttype, byte[]>>();
 512
 513             // Sender provides pubkey, receiver adds signature
 514             // [ECDSA public key] OP_CHECKSIG
 515             templateTuples.Add(
 516                 new Tuple<txnouttype, byte[]>(
 517                     txnouttype.TX_PUBKEY,
 518                     new byte[] {
 519                         (byte)instruction.OP_PUBKEY,
 520                         (byte)instruction.OP_CHECKSIG
 521                     })
 522             );
 523
 524             // Sender provides N pubkeys, receivers provides M signatures
 525             // N [pubkey1] [pubkey2] ... [pubkeyN] M OP_CHECKMULTISIG
 526             // Where N and M are small integer instructions (OP1 ... OP_16)
 527             templateTuples.Add(
 528                 new Tuple<txnouttype, byte[]>(
 529                     txnouttype.TX_MULTISIG,
 530                     new byte[] {
 531                         (byte)instruction.OP_SMALLINTEGER,
 532                         (byte)instruction.OP_PUBKEYS,
 533                         (byte)instruction.OP_SMALLINTEGER,
 534                         (byte)instruction.OP_CHECKMULTISIG
 535                     })
 536             );
 537
 538             // Data-carrying output
 539             // OP_RETURN [up to 80 bytes of data]
 540             templateTuples.Add(
 541                 new Tuple<txnouttype, byte[]>(
 542                     txnouttype.TX_NULL_DATA,
 543                     new byte[] {
 544                         (byte)instruction.OP_RETURN,
 545                         (byte)instruction.OP_SMALLDATA
 546                     })
 547             );
 548
 549             // Nonstandard tx output
 550             typeRet = txnouttype.TX_NONSTANDARD;
 551
 552             foreach (var templateTuple in templateTuples)
 553             {
 554                 var script1 = scriptPubKey;
 555                 var script2 = new CScript(templateTuple.Item2);
 556
 557                 instruction opcode1, opcode2;
 558
 559                 // Compare
 560                 var bq1 = script1.GetByteQUeue();
 561                 var bq2 = script2.GetByteQUeue();
 562
 563                 byte[] args1, args2;
 564
 565                 int last1 = ((byte[])script1).Length -1;
 566                 int last2 = ((byte[])script2).Length - 1;
 567
 568                 while (true)
 569                 {
 570                     if (bq1.CurrentIndex == last1 && bq2.CurrentIndex == last2)
 571                     {
 572                         // Found a match
 573                         typeRet = templateTuple.Item1;
 574                         if (typeRet == txnouttype.TX_MULTISIG)
 575                         {
 576                             // Additional checks for TX_MULTISIG:
 577                             var m = solutions.First().First();
 578                             var n = solutions.Last().First();
 579
 580                             if (m < 1 || n < 1 || m > n || solutions.Count - 2 != n)
 581                             {
 582                                 return false;
 583                             }
 584                         }
 585                         return true;
 586                     }
 587
 588                     if (!GetOp(ref bq1, out opcode1, out args1))
 589                     {
 590                         break;
 591                     }
 592                     if (!GetOp(ref bq2, out opcode2, out args2))
 593                     {
 594                         break;
 595                     }
 596
 597                     // Template matching instructions:
 598                     if (opcode2 == instruction.OP_PUBKEYS)
 599                     {
 600                         while (args1.Count() >= 33 && args1.Count() <= 120)
 601                         {
 602                             solutions.Add(args1);
 603                             if (!GetOp(ref bq1, out opcode1, out args1))
 604                             {
 605                                 break;
 606                             }
 607                         }
 608                         if (!GetOp(ref bq2, out opcode2, out args2))
 609                         {
 610                             break;
 611                         }
 612                         // Normal situation is to fall through
 613                         // to other if/else statements
 614                     }
 615                     if (opcode2 == instruction.OP_PUBKEY)
 616                     {
 617                         int PubKeyLen = args1.Count();
 618                         if (PubKeyLen < 33 || PubKeyLen > 120)
 619                         {
 620                             break;
 621                         }
 622                         solutions.Add(args1);
 623                     }
 624                     else if (opcode2 == instruction.OP_PUBKEYHASH)
 625                     {
 626                         if (args1.Count() != 20) // hash160 size
 627                         {
 628                             break;
 629                         }
 630                         solutions.Add(args1);
 631                     }
 632                     else if (opcode2 == instruction.OP_SMALLINTEGER)
 633                     {
 634                         // Single-byte small integer pushed onto solutions
 635                         try
 636                         {
 637                             var n = (byte)DecodeOP_N(opcode1);
 638                             solutions.Add(new byte[] { n });
 639                         }
 640                         catch (Exception)
 641                         {
 642                             break;
 643                         }
 644                     }
 645                     else if (opcode2 == instruction.OP_SMALLDATA)
 646                     {
 647                         // small pushdata, <= 80 bytes
 648                         if (args1.Length > 80)
 649                         {
 650                             break;
 651                         }
 652                     }
 653                     else if (opcode1 != opcode2 || !args1.SequenceEqual(args2))
 654                     {
 655                         // Others must match exactly
 656                         break;
 657                     }
 658                 }
 659             }
 660
 661             solutions.Clear();
 662             typeRet = txnouttype.TX_NONSTANDARD;
 663
 664             return false;
 665         }
 666
 667         /// <summary>
 668         /// Generation of SignatureHash. This method is responsible for removal of transaction metadata. It's necessary signature can't sign itself.
 669         /// </summary>
 670         /// <param name="script">Spending instructions</param>
 671         /// <param name="txTo">Instance of transaction</param>
 672         /// <param name="nIn">Input number</param>
 673         /// <param name="nHashType">Hash type flag</param>
 674         /// <returns></returns>
 675         public static Hash256 SignatureHash(CScript script, CTransaction txTo, int nIn, int nHashType)
 676         {
 677             if (nIn >= txTo.vin.Length)
 678             {
 679                 var sb = new StringBuilder();
 680                 sb.AppendFormat("ERROR: SignatureHash() : nIn={0} out of range\n", nIn);
 681                 throw new ArgumentOutOfRangeException("nIn", sb.ToString());
 682             }
 683
 684             // Init a copy of transaction
 685             var txTmp = new CTransaction(txTo);
 686
 687             // In case concatenating two scripts ends up with two codeseparators,
 688             // or an extra one at the end, this prevents all those possible incompatibilities.
 689             script.RemoveInstruction(instruction.OP_CODESEPARATOR);
 690
 691             // Blank out other inputs' signatures
 692             for (int i = 0; i < txTmp.vin.Length; i++)
 693             {
 694                 txTmp.vin[i].scriptSig = new CScript();
 695             }
 696             txTmp.vin[nIn].scriptSig = script;
 697
 698             // Blank out some of the outputs
 699             if ((nHashType & 0x1f) == (int)sigflag.SIGHASH_NONE)
 700             {
 701                 // Wildcard payee
 702                 txTmp.vout = new CTxOut[0];
 703
 704                 // Let the others update at will
 705                 for (int i = 0; i < txTmp.vin.Length; i++)
 706                 {
 707                     if (i != nIn)
 708                     {
 709                         txTmp.vin[i].nSequence = 0;
 710                     }
 711                 }
 712             }
 713             else if ((nHashType & 0x1f) == (int)sigflag.SIGHASH_SINGLE)
 714             {
 715                 // Only lock-in the txout payee at same index as txin
 716                 int nOut = nIn;
 717                 if (nOut >= txTmp.vout.Length)
 718                 {
 719                     StringBuilder sb = new StringBuilder();
 720                     sb.AppendFormat("ERROR: SignatureHash() : nOut={0} out of range\n", nOut);
 721                     throw new ArgumentOutOfRangeException("nOut", sb.ToString());
 722                 }
 723                 Array.Resize(ref txTmp.vout, nOut + 1);
 724
 725                 for (int i = 0; i < nOut; i++)
 726                 {
 727                     txTmp.vout[i] = new CTxOut();
 728                 }
 729
 730                 // Let the others update at will
 731                 for (int i = 0; i < txTmp.vin.Length; i++)
 732                 {
 733                     if (i != nIn)
 734                     {
 735                         txTmp.vin[i].nSequence = 0;
 736                     }
 737                 }
 738             }
 739
 740             // Blank out other inputs completely, not recommended for open transactions
 741             if ((nHashType & (int)sigflag.SIGHASH_ANYONECANPAY) != 0)
 742             {
 743                 txTmp.vin[0] = txTmp.vin[nIn];
 744                 Array.Resize(ref txTmp.vin, 1);
 745             }
 746
 747             // Concatenate and hash
 748             var txBytes = (byte[])txTmp;
 749             var nHashTypeBytes = BitConverter.GetBytes(nHashType);
 750
 751             return Hash256.Compute256(ref txBytes, ref nHashTypeBytes);
 752         }
 753
 754         //
 755         // Script is a stack machine (like Forth) that evaluates a predicate
 756         // returning a bool indicating valid or not.  There are no loops.
 757         //
 758
 759         /// <summary>
 760         /// Script machine exception
 761         /// </summary>
 762         public class StackMachineException : Exception
 763         {
 764             public StackMachineException()
 765             {
 766             }
 767
 768             public StackMachineException(string message)
 769                 : base(message)
 770             {
 771             }
 772
 773             public StackMachineException(string message, Exception inner)
 774                 : base(message, inner)
 775             {
 776             }
 777         }
 778
 779         /// <summary>
 780         /// Remove last element from stack
 781         /// </summary>
 782         /// <param name="stack">Stack reference</param>
 783         private static void popstack(ref List<byte[]> stack)
 784         {
 785             int nCount = stack.Count;
 786             if (nCount == 0)
 787                 throw new StackMachineException("popstack() : stack empty");
 788             stack.RemoveAt(nCount - 1);
 789         }
 790
 791         /// <summary>
 792         /// Get element at specified stack depth
 793         /// </summary>
 794         /// <param name="stack">Stack reference</param>
 795         /// <param name="nDepth">Depth</param>
 796         /// <returns>Byte sequence</returns>
 797         private static byte[] stacktop(ref List<byte[]> stack, int nDepth)
 798         {
 799             int nStackElement = stack.Count + nDepth;
 800
 801             if (nDepth >= 0)
 802             {
 803                 StringBuilder sb = new StringBuilder();
 804                 sb.AppendFormat("stacktop() : positive depth ({0}) has no sense.", nDepth);
 805
 806                 throw new StackMachineException(sb.ToString());
 807             }
 808
 809             if (nStackElement < 0)
 810             {
 811                 StringBuilder sb = new StringBuilder();
 812                 sb.AppendFormat("stacktop() : nDepth={0} exceeds real stack depth ({1})", nDepth, stack.Count);
 813
 814                 throw new StackMachineException(sb.ToString());
 815             }
 816
 817             return stack[nStackElement];
 818         }
 819
 820         /// <summary>
 821         /// Cast argument to boolean value
 822         /// </summary>
 823         /// <param name="value">Some byte sequence</param>
 824         /// <returns></returns>
 825         private static bool CastToBool(byte[] arg)
 826         {
 827             for (var i = 0; i < arg.Length; i++)
 828             {
 829                 if (arg[i] != 0)
 830                 {
 831                     // Can be negative zero
 832                     if (i == arg.Length - 1 && arg[i] == 0x80)
 833                     {
 834                         return false;
 835                     }
 836
 837                     return true;
 838                 }
 839             }
 840
 841             return false;
 842         }
 843
 844         /// <summary>
 845         /// Cast argument to integer value
 846         /// </summary>
 847         /// <param name="value"></param>
 848         /// <returns></returns>
 849         private static BigInteger CastToBigInteger(byte[] value)
 850         {
 851             if (value.Length > 4)
 852             {
 853                 throw new StackMachineException("CastToBigInteger() : overflow");
 854             }
 855
 856             return new BigInteger(value);
 857         }
 858
 859         /// <summary>
 860         /// Execution of script
 861         /// </summary>
 862         /// <param name="stack"></param>
 863         /// <param name="script">Script to execute</param>
 864         /// <param name="txTo">Transaction instance</param>
 865         /// <param name="nIn">Input number</param>
 866         /// <param name="flags">Signature checking flags</param>
 867         /// <param name="nHashType">Hash type flag</param>
 868         /// <returns></returns>
 869         public static bool EvalScript(ref List<byte[]> stack, CScript script, CTransaction txTo, int nIn, int flags, int nHashType)
 870         {
 871             var scriptBytes = ((byte[])script);
 872
 873             if (scriptBytes.Length > 10000)
 874             {
 875                 return false; // Size limit failed
 876             }
 877
 878             var vfExec = new List<bool>();
 879
 880             int nOpCount = 0;
 881             int nCodeHashBegin = 0;
 882
 883             var falseBytes = new byte[0];
 884             var trueBytes = new byte[] { 0x01 };
 885
 886             var CodeQueue = script.GetByteQUeue();
 887             var altStack = new List<byte[]>();
 888
 889             try
 890             {
 891                 instruction opcode;
 892                 byte[] pushArg;
 893
 894                 while (GetOp(ref CodeQueue, out opcode, out pushArg)) // Read instructions
 895                 {
 896                     bool fExec = vfExec.IndexOf(false) == -1;
 897
 898                     if (pushArg.Length > 520)
 899                     {
 900                         return false; // Script element size limit failed
 901                     }
 902
 903                     if (opcode > instruction.OP_16 && ++nOpCount > 201)
 904                     {
 905                         return false;
 906                     }
 907
 908                     if (fExec && 0 <= opcode && opcode <= instruction.OP_PUSHDATA4)
 909                     {
 910                         stack.Add(pushArg); // Push argument to stack
 911                     }
 912                     else if (fExec || (instruction.OP_IF <= opcode && opcode <= instruction.OP_ENDIF))
 913                         switch (opcode)
 914                         {
 915                             //
 916                             // Disabled instructions
 917                             //
 918                             case instruction.OP_CAT:
 919                             case instruction.OP_SUBSTR:
 920                             case instruction.OP_LEFT:
 921                             case instruction.OP_RIGHT:
 922                             case instruction.OP_INVERT:
 923                             case instruction.OP_AND:
 924                             case instruction.OP_OR:
 925                             case instruction.OP_XOR:
 926                             case instruction.OP_2MUL:
 927                             case instruction.OP_2DIV:
 928                             case instruction.OP_MUL:
 929                             case instruction.OP_DIV:
 930                             case instruction.OP_MOD:
 931                             case instruction.OP_LSHIFT:
 932                             case instruction.OP_RSHIFT:
 933                                 return false;
 934
 935                             //
 936                             // Push integer instructions
 937                             //
 938                             case instruction.OP_1NEGATE:
 939                             case instruction.OP_1:
 940                             case instruction.OP_2:
 941                             case instruction.OP_3:
 942                             case instruction.OP_4:
 943                             case instruction.OP_5:
 944                             case instruction.OP_6:
 945                             case instruction.OP_7:
 946                             case instruction.OP_8:
 947                             case instruction.OP_9:
 948                             case instruction.OP_10:
 949                             case instruction.OP_11:
 950                             case instruction.OP_12:
 951                             case instruction.OP_13:
 952                             case instruction.OP_14:
 953                             case instruction.OP_15:
 954                             case instruction.OP_16:
 955                                 {
 956                                     // ( -- value)
 957                                     BigInteger bn = DecodeOP_N(opcode, true);
 958                                     stack.Add(bn.ToByteArray());
 959                                 }
 960                                 break;
 961
 962                             //
 963                             // Extension
 964                             //
 965                             case instruction.OP_NOP:
 966                             case instruction.OP_NOP1:
 967                             case instruction.OP_NOP2:
 968                             case instruction.OP_NOP3:
 969                             case instruction.OP_NOP4:
 970                             case instruction.OP_NOP5:
 971                             case instruction.OP_NOP6:
 972                             case instruction.OP_NOP7:
 973                             case instruction.OP_NOP8:
 974                             case instruction.OP_NOP9:
 975                             case instruction.OP_NOP10:
 976                                 {
 977                                     // Just do nothing
 978                                 }
 979                                 break;
 980
 981                             //
 982                             // Control
 983                             //
 984                             case instruction.OP_IF:
 985                             case instruction.OP_NOTIF:
 986                                 {
 987                                     // <expression> if [statements] [else [statements]] endif
 988                                     var fValue = false;
 989                                     if (fExec)
 990                                     {
 991                                         if (stack.Count() < 1)
 992                                         {
 993                                             return false;
 994                                         }
 995                                         var vch = stacktop(ref stack, -1);
 996                                         fValue = CastToBool(vch);
 997                                         if (opcode == instruction.OP_NOTIF)
 998                                         {
 999                                             fValue = !fValue;
1000                                         }
1001                                         popstack(ref stack);
1002                                     }
1003                                     vfExec.Add(fValue);
1004                                 }
1005                                 break;
1006
1007                             case instruction.OP_ELSE:
1008                                 {
1009                                     int nExecCount = vfExec.Count();
1010                                     if (nExecCount == 0)
1011                                     {
1012                                         return false;
1013                                     }
1014                                     vfExec[nExecCount - 1] = !vfExec[nExecCount - 1];
1015                                 }
1016                                 break;
1017
1018                             case instruction.OP_ENDIF:
1019                                 {
1020                                     int nExecCount = vfExec.Count();
1021                                     if (nExecCount == 0)
1022                                     {
1023                                         return false;
1024                                     }
1025                                     vfExec.RemoveAt(nExecCount - 1);
1026                                 }
1027                                 break;
1028
1029                             case instruction.OP_VERIFY:
1030                                 {
1031                                     // (true -- ) or
1032                                     // (false -- false) and return
1033                                     if (stack.Count() < 1)
1034                                     {
1035                                         return false;
1036                                     }
1037
1038                                     bool fValue = CastToBool(stacktop(ref stack, -1));
1039                                     if (fValue)
1040                                     {
1041                                         popstack(ref stack);
1042                                     }
1043                                     else
1044                                     {
1045                                         return false;
1046                                     }
1047                                 }
1048                                 break;
1049
1050                             case instruction.OP_RETURN:
1051                                 {
1052                                     return false;
1053                                 }
1054
1055                             //
1056                             // Stack ops
1057                             //
1058                             case instruction.OP_TOALTSTACK:
1059                                 {
1060                                     if (stack.Count() < 1)
1061                                     {
1062                                         return false;
1063                                     }
1064                                     altStack.Add(stacktop(ref stack, -1));
1065                                     popstack(ref stack);
1066                                 }
1067                                 break;
1068
1069                             case instruction.OP_FROMALTSTACK:
1070                                 {
1071                                     if (altStack.Count() < 1)
1072                                     {
1073                                         return false;
1074                                     }
1075                                     stack.Add(stacktop(ref stack, -1));
1076                                     popstack(ref altStack);
1077                                 }
1078                                 break;
1079
1080                             case instruction.OP_2DROP:
1081                                 {
1082                                     // (x1 x2 -- )
1083                                     if (stack.Count() < 2)
1084                                     {
1085                                         return false;
1086                                     }
1087                                     popstack(ref stack);
1088                                     popstack(ref stack);
1089                                 }
1090                                 break;
1091
1092                             case instruction.OP_2DUP:
1093                                 {
1094                                     // (x1 x2 -- x1 x2 x1 x2)
1095                                     if (stack.Count() < 2)
1096                                     {
1097                                         return false;
1098                                     }
1099                                     var vch1 = stacktop(ref stack, -2);
1100                                     var vch2 = stacktop(ref stack, -1);
1101                                     stack.Add(vch1);
1102                                     stack.Add(vch2);
1103                                 }
1104                                 break;
1105
1106                             case instruction.OP_3DUP:
1107                                 {
1108                                     // (x1 x2 x3 -- x1 x2 x3 x1 x2 x3)
1109                                     if (stack.Count() < 3)
1110                                     {
1111                                         return false;
1112                                     }
1113                                     var vch1 = stacktop(ref stack, -3);
1114                                     var vch2 = stacktop(ref stack, -2);
1115                                     var vch3 = stacktop(ref stack, -1);
1116                                     stack.Add(vch1);
1117                                     stack.Add(vch2);
1118                                     stack.Add(vch3);
1119                                 }
1120                                 break;
1121
1122                             case instruction.OP_2OVER:
1123                                 {
1124                                     // (x1 x2 x3 x4 -- x1 x2 x3 x4 x1 x2)
1125                                     if (stack.Count() < 4)
1126                                     {
1127                                         return false;
1128                                     }
1129                                     var vch1 = stacktop(ref stack, -4);
1130                                     var vch2 = stacktop(ref stack, -3);
1131                                     stack.Add(vch1);
1132                                     stack.Add(vch2);
1133                                 }
1134                                 break;
1135
1136                             case instruction.OP_2ROT:
1137                                 {
1138                                     int nStackDepth = stack.Count();
1139                                     // (x1 x2 x3 x4 x5 x6 -- x3 x4 x5 x6 x1 x2)
1140                                     if (nStackDepth < 6)
1141                                     {
1142                                         return false;
1143                                     }
1144                                     var vch1 = stacktop(ref stack, -6);
1145                                     var vch2 = stacktop(ref stack, -5);
1146                                     stack.RemoveRange(nStackDepth - 6, 2);
1147                                     stack.Add(vch1);
1148                                     stack.Add(vch2);
1149                                 }
1150                                 break;
1151
1152                             case instruction.OP_2SWAP:
1153                                 {
1154                                     // (x1 x2 x3 x4 -- x3 x4 x1 x2)
1155                                     int nStackDepth = stack.Count;
1156                                     if (nStackDepth < 4)
1157                                     {
1158                                         return false;
1159                                     }
1160                                     stack.Swap(nStackDepth - 4, nStackDepth - 2);
1161                                     stack.Swap(nStackDepth - 3, nStackDepth - 1);
1162                                 }
1163                                 break;
1164
1165                             case instruction.OP_IFDUP:
1166                                 {
1167                                     // (x - 0 | x x)
1168                                     if (stack.Count() < 1)
1169                                     {
1170                                         return false;
1171                                     }
1172
1173                                     var vch = stacktop(ref stack, -1);
1174
1175                                     if (CastToBool(vch))
1176                                     {
1177                                         stack.Add(vch);
1178                                     }
1179                                 }
1180                                 break;
1181
1182                             case instruction.OP_DEPTH:
1183                                 {
1184                                     // -- stacksize
1185                                     BigInteger bn = new BigInteger((ushort)stack.Count());
1186                                     stack.Add(bn.ToByteArray());
1187                                 }
1188                                 break;
1189
1190                             case instruction.OP_DROP:
1191                                 {
1192                                     // (x -- )
1193                                     if (stack.Count() < 1)
1194                                     {
1195                                         return false;
1196                                     }
1197
1198                                     popstack(ref stack);
1199                                 }
1200                                 break;
1201
1202                             case instruction.OP_DUP:
1203                                 {
1204                                     // (x -- x x)
1205                                     if (stack.Count() < 1)
1206                                     {
1207                                         return false;
1208                                     }
1209
1210                                     var vch = stacktop(ref stack, -1);
1211                                     stack.Add(vch);
1212                                 }
1213                                 break;
1214
1215                             case instruction.OP_NIP:
1216                                 {
1217                                     // (x1 x2 -- x2)
1218                                     int nStackDepth = stack.Count();
1219                                     if (nStackDepth < 2)
1220                                     {
1221                                         return false;
1222                                     }
1223
1224                                     stack.RemoveAt(nStackDepth - 2);
1225                                 }
1226                                 break;
1227
1228                             case instruction.OP_OVER:
1229                                 {
1230                                     // (x1 x2 -- x1 x2 x1)
1231                                     if (stack.Count() < 2)
1232                                     {
1233                                         return false;
1234                                     }
1235
1236                                     var vch = stacktop(ref stack, -2);
1237                                     stack.Add(vch);
1238                                 }
1239                                 break;
1240
1241                             case instruction.OP_PICK:
1242                             case instruction.OP_ROLL:
1243                                 {
1244                                     // (xn ... x2 x1 x0 n - xn ... x2 x1 x0 xn)
1245                                     // (xn ... x2 x1 x0 n - ... x2 x1 x0 xn)
1246
1247                                     int nStackDepth = stack.Count();
1248                                     if (nStackDepth < 2)
1249                                     {
1250                                         return false;
1251                                     }
1252
1253                                     int n = (int)CastToBigInteger(stacktop(ref stack, -1));
1254                                     popstack(ref stack);
1255
1256                                     if (n < 0 || n >= stack.Count())
1257                                     {
1258                                         return false;
1259                                     }
1260
1261                                     var vch = stacktop(ref stack, -n - 1);
1262                                     if (opcode == instruction.OP_ROLL)
1263                                     {
1264                                         stack.RemoveAt(nStackDepth - n - 1);
1265                                     }
1266
1267                                     stack.Add(vch);
1268                                 }
1269                                 break;
1270
1271                             case instruction.OP_ROT:
1272                                 {
1273                                     // (x1 x2 x3 -- x2 x3 x1)
1274                                     //  x2 x1 x3  after first swap
1275                                     //  x2 x3 x1  after second swap
1276                                     int nStackDepth = stack.Count();
1277                                     if (nStackDepth < 3)
1278                                     {
1279                                         return false;
1280                                     }
1281                                     stack.Swap(nStackDepth - 3, nStackDepth - 2);
1282                                     stack.Swap(nStackDepth - 2, nStackDepth - 1);
1283
1284                                 }
1285                                 break;
1286
1287                             case instruction.OP_SWAP:
1288                                 {
1289                                     // (x1 x2 -- x2 x1)
1290                                     int nStackDepth = stack.Count();
1291                                     if (nStackDepth < 2)
1292                                     {
1293                                         return false;
1294                                     }
1295                                     stack.Swap(nStackDepth - 2, nStackDepth - 1);
1296                                 }
1297                                 break;
1298
1299                             case instruction.OP_TUCK:
1300                                 {
1301                                     // (x1 x2 -- x2 x1 x2)
1302                                     int nStackDepth = stack.Count();
1303                                     if (nStackDepth < 2)
1304                                     {
1305                                         return false;
1306                                     }
1307                                     var vch = stacktop(ref stack, -1);
1308                                     stack.Insert(nStackDepth - 2, vch);
1309                                 }
1310                                 break;
1311
1312
1313                             case instruction.OP_SIZE:
1314                                 {
1315                                     // (in -- in size)
1316                                     if (stack.Count() < 1)
1317                                     {
1318                                         return false;
1319                                     }
1320
1321                                     var bnSize = new BigInteger((ushort)stacktop(ref stack, -1).Count());
1322                                     stack.Add(bnSize.ToByteArray());
1323                                 }
1324                                 break;
1325
1326
1327                             //
1328                             // Bitwise logic
1329                             //
1330                             case instruction.OP_EQUAL:
1331                             case instruction.OP_EQUALVERIFY:
1332                                 //case instruction.OP_NOTEQUAL: // use OP_NUMNOTEQUAL
1333                                 {
1334                                     // (x1 x2 - bool)
1335                                     if (stack.Count() < 2)
1336                                     {
1337                                         return false;
1338                                     }
1339
1340                                     var vch1 = stacktop(ref stack, -2);
1341                                     var vch2 = stacktop(ref stack, -1);
1342                                     bool fEqual = (vch1.SequenceEqual(vch2));
1343                                     // OP_NOTEQUAL is disabled because it would be too easy to say
1344                                     // something like n != 1 and have some wiseguy pass in 1 with extra
1345                                     // zero bytes after it (numerically, 0x01 == 0x0001 == 0x000001)
1346                                     //if (opcode == instruction.OP_NOTEQUAL)
1347                                     //    fEqual = !fEqual;
1348                                     popstack(ref stack);
1349                                     popstack(ref stack);
1350                                     stack.Add(fEqual ? trueBytes : falseBytes);
1351
1352                                     if (opcode == instruction.OP_EQUALVERIFY)
1353                                     {
1354                                         if (fEqual)
1355                                         {
1356                                             popstack(ref stack);
1357                                         }
1358                                         else
1359                                         {
1360                                             return false;
1361                                         }
1362                                     }
1363                                 }
1364                                 break;
1365
1366
1367                             //
1368                             // Numeric
1369                             //
1370                             case instruction.OP_1ADD:
1371                             case instruction.OP_1SUB:
1372                             case instruction.OP_NEGATE:
1373                             case instruction.OP_ABS:
1374                             case instruction.OP_NOT:
1375                             case instruction.OP_0NOTEQUAL:
1376                                 {
1377                                     // (in -- out)
1378                                     if (stack.Count() < 1)
1379                                     {
1380                                         return false;
1381                                     }
1382
1383                                     var bn = CastToBigInteger(stacktop(ref stack, -1));
1384                                     switch (opcode)
1385                                     {
1386                                         case instruction.OP_1ADD:
1387                                             bn = bn + 1;
1388                                             break;
1389                                         case instruction.OP_1SUB:
1390                                             bn = bn - 1;
1391                                             break;
1392                                         case instruction.OP_NEGATE:
1393                                             bn = -bn;
1394                                             break;
1395                                         case instruction.OP_ABS:
1396                                             bn = BigInteger.Abs(bn);
1397                                             break;
1398                                         case instruction.OP_NOT:
1399                                             bn = bn == 0 ? 1 : 0;
1400                                             break;
1401                                         case instruction.OP_0NOTEQUAL:
1402                                             bn = bn != 0 ? 1 : 0;
1403                                             break;
1404                                     }
1405
1406                                     popstack(ref stack);
1407                                     stack.Add(bn.ToByteArray());
1408                                 }
1409                                 break;
1410
1411                             case instruction.OP_ADD:
1412                             case instruction.OP_SUB:
1413                             case instruction.OP_BOOLAND:
1414                             case instruction.OP_BOOLOR:
1415                             case instruction.OP_NUMEQUAL:
1416                             case instruction.OP_NUMEQUALVERIFY:
1417                             case instruction.OP_NUMNOTEQUAL:
1418                             case instruction.OP_LESSTHAN:
1419                             case instruction.OP_GREATERTHAN:
1420                             case instruction.OP_LESSTHANOREQUAL:
1421                             case instruction.OP_GREATERTHANOREQUAL:
1422                             case instruction.OP_MIN:
1423                             case instruction.OP_MAX:
1424                                 {
1425                                     // (x1 x2 -- out)
1426                                     if (stack.Count() < 2)
1427                                     {
1428                                         return false;
1429                                     }
1430
1431                                     var bn1 = CastToBigInteger(stacktop(ref stack, -2));
1432                                     var bn2 = CastToBigInteger(stacktop(ref stack, -1));
1433                                     BigInteger bn = 0;
1434
1435                                     switch (opcode)
1436                                     {
1437                                         case instruction.OP_ADD:
1438                                             bn = bn1 + bn2;
1439                                             break;
1440                                         case instruction.OP_SUB:
1441                                             bn = bn1 - bn2;
1442                                             break;
1443                                         case instruction.OP_BOOLAND:
1444                                             bn = (bn1 != 0 && bn2 != 0) ? 1 : 0;
1445                                             break;
1446                                         case instruction.OP_BOOLOR:
1447                                             bn = (bn1 != 0 || bn2 != 0) ? 1 : 0;
1448                                             break;
1449                                         case instruction.OP_NUMEQUAL:
1450                                             bn = (bn1 == bn2) ? 1 : 0;
1451                                             break;
1452                                         case instruction.OP_NUMEQUALVERIFY:
1453                                             bn = (bn1 == bn2) ? 1 : 0;
1454                                             break;
1455                                         case instruction.OP_NUMNOTEQUAL:
1456                                             bn = (bn1 != bn2) ? 1 : 0;
1457                                             break;
1458                                         case instruction.OP_LESSTHAN:
1459                                             bn = (bn1 < bn2) ? 1 : 0;
1460                                             break;
1461                                         case instruction.OP_GREATERTHAN:
1462                                             bn = (bn1 > bn2) ? 1 : 0;
1463                                             break;
1464                                         case instruction.OP_LESSTHANOREQUAL:
1465                                             bn = (bn1 <= bn2) ? 1 : 0;
1466                                             break;
1467                                         case instruction.OP_GREATERTHANOREQUAL:
1468                                             bn = (bn1 >= bn2) ? 1 : 0;
1469                                             break;
1470                                         case instruction.OP_MIN:
1471                                             bn = (bn1 < bn2 ? bn1 : bn2);
1472                                             break;
1473                                         case instruction.OP_MAX:
1474                                             bn = (bn1 > bn2 ? bn1 : bn2);
1475                                             break;
1476                                     }
1477
1478                                     popstack(ref stack);
1479                                     popstack(ref stack);
1480                                     stack.Add(bn.ToByteArray());
1481
1482                                     if (opcode == instruction.OP_NUMEQUALVERIFY)
1483                                     {
1484                                         if (CastToBool(stacktop(ref stack, -1)))
1485                                         {
1486                                             popstack(ref stack);
1487                                         }
1488                                         else
1489                                         {
1490                                             return false;
1491                                         }
1492                                     }
1493                                 }
1494                                 break;
1495
1496                             case instruction.OP_WITHIN:
1497                                 {
1498                                     // (x min max -- out)
1499                                     if (stack.Count() < 3)
1500                                     {
1501                                         return false;
1502                                     }
1503
1504                                     var bn1 = CastToBigInteger(stacktop(ref stack, -3));
1505                                     var bn2 = CastToBigInteger(stacktop(ref stack, -2));
1506                                     var bn3 = CastToBigInteger(stacktop(ref stack, -1));
1507
1508                                     bool fValue = (bn2 <= bn1 && bn1 < bn3);
1509
1510                                     popstack(ref stack);
1511                                     popstack(ref stack);
1512                                     popstack(ref stack);
1513
1514                                     stack.Add(fValue ? trueBytes : falseBytes);
1515                                 }
1516                                 break;
1517
1518                             //
1519                             // Crypto
1520                             //
1521                             case instruction.OP_RIPEMD160:
1522                             case instruction.OP_SHA1:
1523                             case instruction.OP_SHA256:
1524                             case instruction.OP_HASH160:
1525                             case instruction.OP_HASH256:
1526                                 {
1527                                     // (in -- hash)
1528                                     if (stack.Count() < 1)
1529                                     {
1530                                         return false;
1531                                     }
1532                                     Hash hash = null;
1533                                     var data = stacktop(ref stack, -1);
1534
1535                                     switch (opcode)
1536                                     {
1537                                         case instruction.OP_HASH160:
1538                                             hash = Hash160.Compute160(data);
1539                                             break;
1540                                         case instruction.OP_HASH256:
1541                                             hash = Hash256.Compute256(data);
1542                                             break;
1543                                         case instruction.OP_SHA1:
1544                                             hash = SHA1.Compute1(data);
1545                                             break;
1546                                         case instruction.OP_SHA256:
1547                                             hash = SHA256.Compute256(data);
1548                                             break;
1549                                         case instruction.OP_RIPEMD160:
1550                                             hash = RIPEMD160.Compute160(data);
1551                                             break;
1552                                     }
1553                                     popstack(ref stack);
1554                                     stack.Add(hash);
1555                                 }
1556                                 break;
1557
1558                             case instruction.OP_CODESEPARATOR:
1559                                 {
1560                                     // Hash starts after the code separator
1561                                     nCodeHashBegin = CodeQueue.CurrentIndex;
1562                                 }
1563                                 break;
1564
1565                             case instruction.OP_CHECKSIG:
1566                             case instruction.OP_CHECKSIGVERIFY:
1567                                 {
1568                                     // (sig pubkey -- bool)
1569                                     if (stack.Count() < 2)
1570                                     {
1571                                         return false;
1572                                     }
1573
1574                                     var sigBytes = stacktop(ref stack, -2);
1575                                     var pubkeyBytes = stacktop(ref stack, -1);
1576
1577                                     // Subset of script starting at the most recent codeseparator
1578                                     var scriptCode = new CScript(scriptBytes.Skip(nCodeHashBegin).ToArray());
1579
1580                                     // There's no way for a signature to sign itself
1581                                     scriptCode.RemovePattern(sigBytes);
1582
1583                                     bool fSuccess = IsCanonicalSignature(sigBytes, flags) && IsCanonicalPubKey(pubkeyBytes, flags) && CheckSig(sigBytes, pubkeyBytes, scriptCode, txTo, nIn, nHashType, flags);
1584
1585                                     popstack(ref stack);
1586                                     popstack(ref stack);
1587
1588                                     stack.Add(fSuccess ? trueBytes : falseBytes);
1589
1590                                     if (opcode == instruction.OP_CHECKSIGVERIFY)
1591                                     {
1592                                         if (fSuccess)
1593                                         {
1594                                             popstack(ref stack);
1595                                         }
1596                                         else
1597                                         {
1598                                             return false;
1599                                         }
1600                                     }
1601                                 }
1602                                 break;
1603
1604                             case instruction.OP_CHECKMULTISIG:
1605                             case instruction.OP_CHECKMULTISIGVERIFY:
1606                                 {
1607                                     // ([sig ...] num_of_signatures [pubkey ...] num_of_pubkeys -- bool)
1608
1609                                     int i = 1;
1610                                     if (stack.Count() < i)
1611                                     {
1612                                         return false;
1613                                     }
1614
1615                                     int nKeysCount = (int)CastToBigInteger(stacktop(ref stack, -i));
1616                                     if (nKeysCount < 0 || nKeysCount > 20)
1617                                     {
1618                                         return false;
1619                                     }
1620                                     nOpCount += nKeysCount;
1621                                     if (nOpCount > 201)
1622                                     {
1623                                         return false;
1624                                     }
1625                                     int ikey = ++i;
1626                                     i += nKeysCount;
1627                                     if (stack.Count() < i)
1628                                     {
1629                                         return false;
1630                                     }
1631
1632                                     int nSigsCount = (int)CastToBigInteger(stacktop(ref stack, -i));
1633                                     if (nSigsCount < 0 || nSigsCount > nKeysCount)
1634                                     {
1635                                         return false;
1636                                     }
1637                                     int isig = ++i;
1638                                     i += nSigsCount;
1639                                     if (stack.Count() < i)
1640                                     {
1641                                         return false;
1642                                     }
1643
1644                                     // Subset of script starting at the most recent codeseparator
1645                                     var scriptCode = new CScript(scriptBytes.Skip(nCodeHashBegin).ToArray());
1646
1647                                     // There is no way for a signature to sign itself, so we need to drop the signatures
1648                                     for (int k = 0; k < nSigsCount; k++)
1649                                     {
1650                                         var vchSig = stacktop(ref stack, -isig - k);
1651                                         scriptCode.RemovePattern(vchSig);
1652                                     }
1653
1654                                     bool fSuccess = true;
1655                                     while (fSuccess && nSigsCount > 0)
1656                                     {
1657                                         var sigBytes = stacktop(ref stack, -isig);
1658                                         var pubKeyBytes = stacktop(ref stack, -ikey);
1659
1660                                         // Check signature
1661                                         bool fOk = IsCanonicalSignature(sigBytes, flags) && IsCanonicalPubKey(pubKeyBytes, flags) && CheckSig(sigBytes, pubKeyBytes, scriptCode, txTo, nIn, nHashType, flags);
1662
1663                                         if (fOk)
1664                                         {
1665                                             isig++;
1666                                             nSigsCount--;
1667                                         }
1668                                         ikey++;
1669                                         nKeysCount--;
1670
1671                                         // If there are more signatures left than keys left,
1672                                         // then too many signatures have failed
1673                                         if (nSigsCount > nKeysCount)
1674                                         {
1675                                             fSuccess = false;
1676                                         }
1677                                     }
1678
1679                                     while (i-- > 1)
1680                                     {
1681                                         popstack(ref stack);
1682                                     }
1683
1684                                     // A bug causes CHECKMULTISIG to consume one extra argument
1685                                     // whose contents were not checked in any way.
1686                                     //
1687                                     // Unfortunately this is a potential source of mutability,
1688                                     // so optionally verify it is exactly equal to zero prior
1689                                     // to removing it from the stack.
1690                                     if (stack.Count() < 1)
1691                                     {
1692                                         return false;
1693                                     }
1694                                     if ((flags & (int)scriptflag.SCRIPT_VERIFY_NULLDUMMY) != 0 && stacktop(ref stack, -1).Count() != 0)
1695                                     {
1696                                         return false; // CHECKMULTISIG dummy argument not null
1697                                     }
1698                                     popstack(ref stack);
1699
1700                                     stack.Add(fSuccess ? trueBytes : falseBytes);
1701
1702                                     if (opcode == instruction.OP_CHECKMULTISIGVERIFY)
1703                                     {
1704                                         if (fSuccess)
1705                                         {
1706                                             popstack(ref stack);
1707                                         }
1708                                         else
1709                                         {
1710                                             return false;
1711                                         }
1712                                     }
1713                                 }
1714                                 break;
1715
1716                             default:
1717                                 return false;
1718                         }
1719
1720                     // Size limits
1721                     if (stack.Count() + altStack.Count() > 1000)
1722                     {
1723                         return false;
1724                     }
1725                 }
1726             }
1727             catch (Exception)
1728             {
1729                 // If there are any exceptions then just return false.
1730                 return false;
1731             }
1732
1733             if (vfExec.Count() != 0)
1734             {
1735                 // Something went wrong with conditional instructions.
1736                 return false;
1737             }
1738
1739             return true;
1740         }
1741
1742
1743         public static bool IsCanonicalPubKey(byte[] pubKeyBytes, int flags)
1744         {
1745             if ((flags & (int)scriptflag.SCRIPT_VERIFY_STRICTENC) == 0)
1746                 return true;
1747
1748             if (pubKeyBytes.Length < 33)
1749                 return false;  // Non-canonical public key: too short
1750             if (pubKeyBytes[0] == 0x04)
1751             {
1752                 if (pubKeyBytes.Length != 65)
1753                     return false; // Non-canonical public key: invalid length for uncompressed key
1754             }
1755             else if (pubKeyBytes[0] == 0x02 || pubKeyBytes[0] == 0x03)
1756             {
1757                 if (pubKeyBytes.Length != 33)
1758                     return false; // Non-canonical public key: invalid length for compressed key
1759             }
1760             else
1761             {
1762                 return false; // Non-canonical public key: compressed nor uncompressed
1763             }
1764             return true;
1765         }
1766
1767         public static bool IsCanonicalSignature(byte[] sigBytes, int flags)
1768         {
1769             // STUB
1770
1771             return true;
1772         }
1773
1774         /// <summary>
1775         /// Check signature.
1776         /// </summary>
1777         /// <param name="sigBytes">Signature</param>
1778         /// <param name="pubkeyBytes">Public key</param>
1779         /// <param name="script">Spending script</param>
1780         /// <param name="txTo">CTransaction instance</param>
1781         /// <param name="nIn">Input number</param>
1782         /// <param name="nHashType">Hashing type flag</param>
1783         /// <param name="flags">Signature checking flags</param>
1784         /// <returns>Checking result</returns>
1785         public static bool CheckSig(byte[] sigBytes, byte[] pubkeyBytes, CScript script, CTransaction txTo, int nIn, int nHashType, int flags)
1786         {
1787             CPubKey pubkey;
1788
1789             try
1790             {
1791                 // Trying to initialize the public key instance
1792
1793                 pubkey = new CPubKey(pubkeyBytes);
1794             }
1795             catch (Exception)
1796             {
1797                 // Exception occurred while initializing the public key
1798
1799                 return false;
1800             }
1801
1802             if (!pubkey.IsValid)
1803             {
1804                 return false;
1805             }
1806
1807             if (sigBytes.Length == 0)
1808             {
1809                 return false;
1810             }
1811
1812             // Hash type is one byte tacked on to the end of the signature
1813             if (nHashType == 0)
1814             {
1815                 nHashType = sigBytes.Last();
1816             }
1817             else if (nHashType != sigBytes.Last())
1818             {
1819                 return false;
1820             }
1821
1822             // Remove hash type
1823             Array.Resize(ref sigBytes, sigBytes.Length - 1);
1824
1825             var sighash = SignatureHash(script, txTo, nIn, nHashType);
1826
1827             if (!pubkey.VerifySignature(sighash, sigBytes))
1828             {
1829                 return false;
1830             }
1831
1832             return true;
1833         }
1834
1835         /// <summary>
1836         /// Evaluates the both scriptSig and scriptPubKey.
1837         /// </summary>
1838         /// <param name="scriptSig"></param>
1839         /// <param name="scriptPubKey"></param>
1840         /// <param name="txTo">Transaction</param>
1841         /// <param name="nIn">Input number</param>
1842         /// <param name="flags">Script validation flags</param>
1843         /// <param name="nHashType">Hash type flag</param>
1844         /// <returns></returns>
1845         public static bool VerifyScript(CScript scriptSig, CScript scriptPubKey, CTransaction txTo, int nIn, int flags, int nHashType)
1846         {
1847             var stack = new List<byte[]>();
1848             List<byte[]> stackCopy = null;
1849
1850             if (!EvalScript(ref stack, scriptSig, txTo, nIn, flags, nHashType))
1851             {
1852                 return false;
1853             }
1854
1855             if ((flags & (int)scriptflag.SCRIPT_VERIFY_P2SH) != 0)
1856             {
1857                 stackCopy = new List<byte[]>(stack);
1858             }
1859
1860             if (!EvalScript(ref stack, scriptPubKey, txTo, nIn, flags, nHashType))
1861             {
1862                 return false;
1863             }
1864
1865             if (stack.Count == 0 || CastToBool(stack.Last()) == false)
1866             {
1867                 return false;
1868             }
1869
1870             // Additional validation for spend-to-script-hash transactions:
1871             if ((flags & (int)scriptflag.SCRIPT_VERIFY_P2SH) != 0 && scriptPubKey.IsPayToScriptHash)
1872             {
1873                 if (!scriptSig.IsPushOnly) // scriptSig must be literals-only
1874                 {
1875                     return false;
1876                 }
1877
1878                 // stackCopy cannot be empty here, because if it was the
1879                 // P2SH  HASH <> EQUAL  scriptPubKey would be evaluated with
1880                 // an empty stack and the EvalScript above would return false.
1881
1882                 if (stackCopy.Count == 0)
1883                 {
1884                     throw new StackMachineException("Fatal script validation error.");
1885                 }
1886
1887                 var pubKey2 = new CScript(stackCopy.Last());
1888                 popstack(ref stackCopy);
1889
1890                 if (!EvalScript(ref stackCopy, pubKey2, txTo, nIn, flags, nHashType))
1891                     return false;
1892                 if (stackCopy.Count == 0)
1893                     return false;
1894
1895                 return CastToBool(stackCopy.Last());
1896             }
1897
1898             return true;
1899         }
1900     };
1901 }