Difference between revisions of "Script"

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Bitcoin uses a scripting system for [[transactions]]. [[Wikipedia:FORTH|Forth]]-like, Script is simple, stack-based, and processed from left to right. It is purposefully not Turing-complete, with no loops.
 
Bitcoin uses a scripting system for [[transactions]]. [[Wikipedia:FORTH|Forth]]-like, Script is simple, stack-based, and processed from left to right. It is purposefully not Turing-complete, with no loops.
  
A script is essentially a list of instructions recorded with each transaction that describe how the next person wanting to spend the Bitcoins being transferred can gain access to them.
+
A script is essentially a list of instructions recorded with each transaction that describe how the next person wanting to spend the Bitcoins being transferred can gain access to them. The script for a typical Bitcoin transfer to destination Bitcoin address D simply encumbers future spending of the bitcoins with two things: the spender must provide
 
 
Scripts are big-endian and their sequences of bytes is interpreted as a sequence of opcodes with operands. Only opcodes with byte values less than 0x4f have additional operands.
 
 
 
== Scripts and Bitcoin transactions ==
 
The script for a typical Bitcoin transfer to destination Bitcoin address D simply encumbers future spending of the bitcoins with two things: the spender must provide
 
 
# a public key that, when hashed, yields destination address D embedded in the script, and
 
# a public key that, when hashed, yields destination address D embedded in the script, and
 
# a signature to show evidence of the private key corresponding to the public key just provided.
 
# a signature to show evidence of the private key corresponding to the public key just provided.
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Scripting provides the flexibility to change the parameters of what's needed to spend transferred Bitcoins.  For example, the scripting system could be used to require two private keys, or a combination of several, or even no keys at all.
 
Scripting provides the flexibility to change the parameters of what's needed to spend transferred Bitcoins.  For example, the scripting system could be used to require two private keys, or a combination of several, or even no keys at all.
  
A transaction is valid if nothing in the combined script triggers failure and the top stack item exists and is true (non-zero).  The party who originally ''stored'' the Bitcoins now being spent, dictates the script operations that will occur ''last'' in order to release them for use in another transaction.  The party wanting to spend them must provide the input(s) to the previously recorded script that results in those operations occurring last leaving behind true (non-zero) on the stack.<br>
+
A transaction is valid if nothing in the combined script triggers failure and the top stack item is true (non-zero).  The party who originally ''sent'' the Bitcoins now being spent, dictates the script operations that will occur ''last'' in order to release them for use in another transaction.  The party wanting to spend them must provide the input(s) to the previously recorded script that results in those operations occurring last leaving behind true (non-zero).
Only the very first transaction in each bitcoin block has no input script (the entry there is called "coinbase"), because the Bitcoins created with the block are created from hot air and not released by a previous recorded txout-script.
 
 
 
== Stack ==
 
 
 
The stacks hold byte vectors (there is the (main) stack and an alternative stack). Byte vectors are interpreted as little-endian variable-length integers with the most significant bit determining the sign of the integer.  Thus 0x81 represents -1.  0x80 is another representation of zero (so called negative 0).  Byte vectors are interpreted as Booleans where False is represented by any representation of zero, and True is represented by any representation of non-zero.
 
  
== Opcode overview ==
+
Scripts are big-endian.
  
For each opcode is given: its nemonic without the leading OP_, its hexadecimal byte value, the number of stack items needed (poped) during execution, a semicolon and the number of stack items which has been pushed (after execution). A * after the needed stack items indicates that further bytes from the script following the current opcode are needed. A # indicates that items on the alternative stack are poped/pushed. A @ indicates that further (global) data from the transaction is needed. A / indicates alternatives of a value. <br/>
+
The stacks hold byte vectors. Byte vectors are interpreted as little-endian variable-length integers with the most significant bit determining the sign of the integer. Thus 0x81 represents -1. 0x80 is another representation of zero (so called negative 0).  Byte vectors are interpreted as Booleans where False is represented by any representation of zero, and True is represented by any representation of non-zero.
Different colors indicate different semantic execution groups of opcodes:
 
{| style="background:none; font-size:100%; padding:0; border-collapse:collapse; text-align:center; line-height:2em;" border="0" align="center"
 
|-
 
| style="border:1px solid #aaaaaa; background-color:gold;" | copy a fixed number of bytes but at most 75 onto stack
 
| style="border:1px solid #aaaaaa; background-color:#ffff00;" | copy bytes onto stack which number is given by a 1, 2 or 4 byte value.
 
| style="border:1px solid #aaaaaa; background-color:#ffb000;" | copy 1 specific byte onto stack
 
|-
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | undefined opcode
 
| style="border:1px solid #aaaaaa; background-color:#f0f0f0;" | a pseudo-opcode, unassigned for scripts
 
|-
 
| style="border:1px solid #aaaaaa; background-color:#00d000;" | NOP or opcode is part of a IF-flow-control construction
 
|-
 
| style="border:1px solid #aaaaaa; background-color:#00ff00;" | (stack conditionally) invalidation of the script this opcode is part of
 
|-
 
| style="border:1px solid #aaaaaa; background-color:#ff8080;" | stack item is moved between main stack and alternate stack
 
| style="border:1px solid #aaaaaa; background-color:#ff4040;" | stack item(s) is/are moved, copied or deleted
 
|-
 
| style="border:1px solid #aaaaaa; background-color:#f000f0;" | byte vectors are appended or divided or their size is determined
 
| style="border:1px solid #aaaaaa; background-color:#c000ff;" | byte vectors are interpreted bit-position-independently
 
|-
 
| style="border:1px solid #aaaaaa; background-color:#8000ff;" | byte vectors are interpreted and processed as signed integers
 
|-
 
| style="border:1px solid #aaaaaa; background-color:#00c0f0;" | a hash value is computed or a signature checked
 
|}
 
<p>
 
===Opcode byte-matrix===
 
The opcode value 0x00 with nemonic OP_FALSE is also named OP_0 and the opcode value 0x51 with nemonic OP_1 as also named OP_TRUE.
 
{| style="background:none; font-size:100%; padding:0; border-collapse:collapse; text-align:center; line-height:2em;" border="0" align="center"
 
|-
 
| style="border:1px solid #aaaaaa; background-color:gold;" |_FALSE<br/> 0x00 <br/> 0 ; 1(0)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x01<br/> 0 *; 1(1)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x02<br/> 0 *; 1(2)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x03<br/> 0 *; 1(3)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x04<br/> 0 *; 1(4)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x04<br/> 0 *; 1(5)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x06<br/> 0 *; 1(6)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x07<br/> 0 *; 1(7)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x08<br/> 0 *; 1(8)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x09<br/> 0 *; 1(9)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x0a<br/> 0 *; 1(10)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x0b<br/> 0 *; 1(11)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x0c<br/> 0 *; 1(12)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x0d<br/> 0 *; 1(13)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x0e<br/> 0 *; 1(14)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x0f<br/> 0 *; 1(15)
 
|-
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x10 <br/> 0 *; 1(16)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x11 <br/> 0 *; 1(17)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x12 <br/> 0 *; 1(18)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x13 <br/> 0 *; 1(19)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x14 <br/> 0 *; 1(20)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x15 <br/> 0 *; 1(21)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x16 <br/> 0 *; 1(22)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x17 <br/> 0 *; 1(23)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x18 <br/> 0 *; 1(24)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x19 <br/> 0 *; 1(25)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x1a <br/> 0 *; 1(26)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x1b <br/> 0 *; 1(27)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x1c <br/> 0 *; 1(28)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x1d <br/> 0 *; 1(29)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x1e <br/> 0 *; 1(30)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x1f <br/> 0 *; 1(31)
 
|-
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x20 <br/> 0 *; 1(32)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x21 <br/> 0 *; 1(33)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x22 <br/> 0 *; 1(34)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x23 <br/> 0 *; 1(35)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x24 <br/> 0 *; 1(36)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x25 <br/> 0 *; 1(37)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x26 <br/> 0 *; 1(38)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x27 <br/> 0 *; 1(39)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x28 <br/> 0 *; 1(40)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x29 <br/> 0 *; 1(41)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x2a <br/> 0 *; 1(42)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x2b <br/> 0 *; 1(43)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x2c <br/> 0 *; 1(44)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x2d <br/> 0 *; 1(45)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x2e <br/> 0 *; 1(46)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x2f <br/> 0 *; 1(47)
 
|-
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x30 <br/> 0 *; 1(48)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x31 <br/> 0 *; 1(49)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x32 <br/> 0 *; 1(50)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x33 <br/> 0 *; 1(51)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x34 <br/> 0 *; 1(52)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x35 <br/> 0 *; 1(53)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x36 <br/> 0 *; 1(54)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x37 <br/> 0 *; 1(55)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x38 <br/> 0 *; 1(56)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x39 <br/> 0 *; 1(57)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x3a <br/> 0 *; 1(58)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x3b <br/> 0 *; 1(59)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x3c <br/> 0 *; 1(60)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x3d <br/> 0 *; 1(61)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x3e <br/> 0 *; 1(62)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x3f <br/> 0 *; 1(63)
 
|-
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x40 <br/> 0 *; 1(64)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x41 <br/> 0 *; 1(65)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x42 <br/> 0 *; 1(66)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x43 <br/> 0 *; 1(67)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x44 <br/> 0 *; 1(68)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x45 <br/> 0 *; 1(69)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x46 <br/> 0 *; 1(70)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x47 <br/> 0 *; 1(71)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x48 <br/> 0 *; 1(72)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x49 <br/> 0 *; 1(73)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x4a <br/> 0 *; 1(74)
 
| style="border:1px solid #aaaaaa; background-color:gold;" | - <br/> 0x4b <br/> 0 *; 1(75)
 
| style="border:1px solid #aaaaaa; background-color:#ffff00;" | _PUSHDATA1 <br/> 0x4c <br/> 0 *; 1(0 - 255)
 
| style="border:1px solid #aaaaaa; background-color:#ffff00;" | _PUSHDATA2 <br/> 0x4d <br/> 0 *; 1(0 - 2^16-1)
 
| style="border:1px solid #aaaaaa; background-color:#ffff00;" | _PUSHDATA4 <br/> 0x4e <br/> 0 *; 1(0 - 2^32-1)
 
| style="border:1px solid #aaaaaa; background-color:#ffb000;" | _1NEGATE <br/> 0x4f <br/> 0 ; 1(1)
 
|-
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | _RESERVED <br/> 0x50 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffb000;" | _1 <br/> 0x51 <br/> 0 ; 1(1)
 
| style="border:1px solid #aaaaaa; background-color:#ffb000;" | _2 <br/> 0x52 <br/> 0 ; 1(1)
 
| style="border:1px solid #aaaaaa; background-color:#ffb000;" | _3 <br/> 0x53 <br/> 0 ; 1(1)
 
| style="border:1px solid #aaaaaa; background-color:#ffb000;" | _4 <br/> 0x54 <br/> 0 ; 1(1)
 
| style="border:1px solid #aaaaaa; background-color:#ffb000;" | _5 <br/> 0x55 <br/> 0 ; 1(1)
 
| style="border:1px solid #aaaaaa; background-color:#ffb000;" | _6 <br/> 0x56 <br/> 0 ; 1(1)
 
| style="border:1px solid #aaaaaa; background-color:#ffb000;" | _7 <br/> 0x57 <br/> 0 ; 1(1)
 
| style="border:1px solid #aaaaaa; background-color:#ffb000;" | _8 <br/> 0x58 <br/> 0 ; 1(1)
 
| style="border:1px solid #aaaaaa; background-color:#ffb000;" | _9 <br/> 0x59 <br/> 0 ; 1(1)
 
| style="border:1px solid #aaaaaa; background-color:#ffb000;" | _10 <br/> 0x5a <br/> 0 ; 1(1)
 
| style="border:1px solid #aaaaaa; background-color:#ffb000;" | _11 <br/> 0x5b <br/> 0 ; 1(1)
 
| style="border:1px solid #aaaaaa; background-color:#ffb000;" | _12 <br/> 0x5c <br/> 0 ; 1(1)
 
| style="border:1px solid #aaaaaa; background-color:#ffb000;" | _13 <br/> 0x5d <br/> 0 ; 1(1)
 
| style="border:1px solid #aaaaaa; background-color:#ffb000;" | _14 <br/> 0x5e <br/> 0 ; 1(1)
 
| style="border:1px solid #aaaaaa; background-color:#ffb000;" | _15 <br/> 0x5f <br/> 0 ; 1(1)
 
|-
 
| style="border:1px solid #aaaaaa; background-color:#ffb000;" | _16 <br/> 0x60 <br/> 0 ; 1(1)
 
| style="border:1px solid #aaaaaa; background-color:#00d000;" | _NOP <br/> 0x61 <br/> 0 ; 0
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | _VER <br/> 0x62 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#00d000;" | _IF <br/> 0x63 <br/> 1 ; 0
 
| style="border:1px solid #aaaaaa; background-color:#00d000;" | _NOTIF <br/> 0x64 <br/> 1 ; 0
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | _VERIF <br/> 0x65 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | _VERNOTIF <br/> 0x66 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#00d000;" | _ELSE <br/> 0x67 <br/> 0 ; 0
 
| style="border:1px solid #aaaaaa; background-color:#00d000;" | _ENDIF <br/> 0x68 <br/> 0 ; 0
 
| style="border:3px solid #808080; background-color:#00ff00;" | _VERIFY <br/> 0x69 <br/> 1 ; 0/1
 
| style="border:3px solid #808080; background-color:#00ff00;" | _RETURN <br/> 0x6a <br/> 0 ; 0
 
| style="border:1px solid #aaaaaa; background-color:#ff8080;" | _TOALTSTACK <br/> 0x6b <br/> 1 ; 0
 
| style="border:1px solid #aaaaaa; background-color:#ff8080;" | _FROMALTSTACK <br/> 0x6c <br/> 0 #; 1
 
| style="border:1px solid #aaaaaa; background-color:#ff4040;" | _2DROP <br/> 0x6d <br/> 2 ; 0
 
| style="border:1px solid #aaaaaa; background-color:#ff4040;" | _2DUP <br/> 0x6e <br/> 2 ; 4
 
| style="border:1px solid #aaaaaa; background-color:#ff4040;" | _3DUP <br/> 0x6f <br/> 3 ; 6
 
|-
 
| style="border:1px solid #aaaaaa; background-color:#ff4040;" | _2OVER <br/> 0x70 <br/> 4 ; 6
 
| style="border:1px solid #aaaaaa; background-color:#ff4040;" | _2ROT <br/> 0x71 <br/> 6 ; 6
 
| style="border:1px solid #aaaaaa; background-color:#ff4040;" | _2SWAP <br/> 0x72 <br/> 4 ; 4
 
| style="border:1px solid #aaaaaa; background-color:#ff4040;" | _IFDUP <br/> 0x73 <br/> 1 ; 1/2
 
| style="border:1px solid #aaaaaa; background-color:#ff4040;" | _DEPTH <br/> 0x74 <br/> 0 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#ff4040;" | _DROP <br/> 0x75 <br/> 1 ; 0
 
| style="border:1px solid #aaaaaa; background-color:#ff4040;" | _DUP <br/> 0x76 <br/> 1 ; 2
 
| style="border:1px solid #aaaaaa; background-color:#ff4040;" | _NIP <br/> 0x77 <br/> 2 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#ff4040;" | _OVER <br/> 0x78 <br/> 2 ; 3
 
| style="border:1px solid #aaaaaa; background-color:#ff4040;" | _PICK <br/> 0x79 <br/> 1+n+1 ; n+2
 
| style="border:1px solid #aaaaaa; background-color:#ff4040;" | _ROLL <br/> 0x7a <br/> 1+n+1 ; n+1
 
| style="border:1px solid #aaaaaa; background-color:#ff4040;" | _ROT <br/> 0x7b <br/> 3 ; 3
 
| style="border:1px solid #aaaaaa; background-color:#ff4040;" | _SWAP <br/> 0x7c <br/> 2 ; 2
 
| style="border:1px solid #aaaaaa; background-color:#ff4040;" | _TUCK <br/> 0x7d <br/> 2 ; 3
 
| style="border:1px solid #aaaaaa; background-color:#f000f0; color:white" | _CAT <br/> 0x7e <br/> 2 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#f000f0; color:white" | _SUBSTR <br/> 0x7f <br/> 3 ; 1
 
|-
 
| style="border:1px solid #aaaaaa; background-color:#f000f0; color:white" | _LEFT <br/> 0x80 <br/> 2 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#f000f0; color:white" | _RIGHT <br/> 0x81 <br/> 2 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#f000f0;" | _SIZE <br/> 0x82 <br/> 1 ; 2
 
| style="border:1px solid #aaaaaa; background-color:#c000ff; color:white" | _INVERT <br/> 0x83 <br/> 1 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#c000ff; color:white" | _AND <br/> 0x84 <br/> 2 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#c000ff; color:white" | _OR <br/> 0x85 <br/> 2 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#c000ff; color:white" | _XOR <br/> 0x86 <br/> 2 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#c000ff;" | _EQUAL <br/> 0x87 <br/> 2 ; 1
 
| style="border:3px solid #808080; background-color:#c080ff;" | _EQUALVERIFY <br/> 0x88 <br/> 2 ; 0/1
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | _RESERVED1 <br/> 0x89 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | _RESERVED2 <br/> 0x8a <br/>
 
| style="border:1px solid #aaaaaa; background-color:#8000ff;" | _1ADD <br/> 0x8b <br/> 1 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#8000ff;" | _1SUB <br/> 0x8c <br/> 1 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#8000ff; color:white" | _2MUL <br/> 0x8d <br/> 1 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#8000ff; color:white" | _2DIV <br/> 0x8e <br/> 1 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#8000ff;" | _NEGATE <br/> 0x8f <br/> 1 ; 1
 
|-
 
| style="border:1px solid #aaaaaa; background-color:#8000ff;" | _ABS <br/> 0x90 <br/> 1 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#8000ff;" | _NOT <br/> 0x91 <br/> 1 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#8000ff;" | _0NOTEQUAL <br/> 0x92 <br/> 1 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#8000ff;" | _ADD <br/> 0x93 <br/> 2 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#8000ff;" | _SUB <br/> 0x94 <br/> 2 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#8000ff; color:white" | _MUL <br/> 0x95 <br/> 2 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#8000ff; color:white" | _DIV <br/> 0x96 <br/> 2 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#8000ff; color:white" | _MOD <br/> 0x97 <br/> 2 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#8000ff; color:white" | _LSHIFT <br/> 0x98 <br/> 2 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#8000ff; color:white" | _RSHIFT <br/> 0x99 <br/> 2 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#8000ff;" | _BOOLAND <br/> 0x9a <br/> 2 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#8000ff;" | _BOOLOR <br/> 0x9b <br/> 2 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#8000ff;" | _NUMEQUAL <br/> 0x9c <br/> 2 ; 1
 
| style="border:3px solid #808080; background-color:#8080ff;" | _NUMEQUALVERIFY <br/> 0x9d <br/> 2 ; 0/1
 
| style="border:1px solid #aaaaaa; background-color:#8000ff;" | _NUMNOTEQUAL <br/> 0x9e <br/> 2 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#8000ff;" | _LESSTHAN <br/> 0x9f <br/> 2 ; 1
 
|-
 
| style="border:1px solid #aaaaaa; background-color:#8000ff;" | _GREATERTHAN <br/> 0xa0 <br/> 2 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#8000ff;" | _LESSTHANOREQUAL <br/> 0xa1 <br/> 2 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#8000ff;" | _GREATERTHANOREQUAL <br/> 0xa2 <br/> 2 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#8000ff;" | _MIN <br/> 0xa3 <br/> 2 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#8000ff;" | _MAX <br/> 0xa4 <br/> 2 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#8000ff;" | _WITHIN <br/> 0xa5 <br/> 3 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#00c0f0;" | _RIPEMD160 <br/> 0xa6 <br/> 1 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#00c0f0;" | _SHA1 <br/> 0xa7 <br/> 1 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#00c0f0;" | _SHA256 <br/> 0xa8 <br/> 1 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#00c0f0;" | _HASH160 <br/> 0xa9 <br/> 1 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#00c0f0;" | _HASH256 <br/> 0xaa <br/> 1 ; 1
 
| style="border:1px solid #aaaaaa; background-color:#00c0f0;" | _CODESEPARATOR  <br/> 0xab <br/> 0 ; 0
 
| style="border:1px solid #aaaaaa; background-color:#00c0f0;" | _CHECKSIG <br/> 0xac <br/> 2 @; 1
 
| style="border:3px solid #808080; background-color:#a0d0ff;" | _CHECKSIGVERIFY <br/> 0xad <br/> 2 @; 0/1
 
| style="border:1px solid #aaaaaa; background-color:#00c0f0;" | _CHECKMULTISIG <br/> 0xae <br/> 2n+2 @; 1
 
| style="border:3px solid #808080; background-color:#a0d0ff;" | _CHECKMULTISIGVERIFY <br/> 0xaf <br/> 2n+2 @; 0/1
 
|-
 
| style="border:1px solid #aaaaaa; background-color:#00d000;" | _NOP1 <br/> 0xb0 <br/> 0 ; 0
 
| style="border:1px solid #aaaaaa; background-color:#00d000;" | _NOP2 <br/> 0xb1 <br/> 0 ; 0
 
| style="border:1px solid #aaaaaa; background-color:#00d000;" | _NOP3 <br/> 0xb2 <br/> 0 ; 0
 
| style="border:1px solid #aaaaaa; background-color:#00d000;" | _NOP4 <br/> 0xb3 <br/> 0 ; 0
 
| style="border:1px solid #aaaaaa; background-color:#00d000;" | _NOP5 <br/> 0xb4 <br/> 0 ; 0
 
| style="border:1px solid #aaaaaa; background-color:#00d000;" | _NOP6 <br/> 0xb5 <br/> 0 ; 0
 
| style="border:1px solid #aaaaaa; background-color:#00d000;" | _NOP7 <br/> 0xb6 <br/> 0 ; 0
 
| style="border:1px solid #aaaaaa; background-color:#00d000;" | _NOP8 <br/> 0xb7 <br/> 0 ; 0
 
| style="border:1px solid #aaaaaa; background-color:#00d000;" | _NOP9 <br/> 0xb8 <br/> 0 ; 0
 
| style="border:1px solid #aaaaaa; background-color:#00d000;" | _NOP10 <br/> 0xb9 <br/> 0 ; 0
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xba <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xbb <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xbc <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xbd <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xbe <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xbf <br/>
 
|-
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xc0 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xc1 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xc2 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xc3 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xc4 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xc5 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xc6 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xc7 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xc8 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xc9 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xca <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xcb <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xcc <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xcd <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xce <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xcf <br/>
 
|-
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xd0 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xd1 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xd2 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xd3 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xd4 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xd5 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xd6 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xd7 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xd8 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xd9 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xda <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xdb <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xdc <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xdd <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xde <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xdf <br/>
 
|-
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xe0 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xe1 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xe2 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xe3 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xe4 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xe5 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xe6 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xe7 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xe8 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xe9 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xea <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xeb <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xec <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xed <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xee <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xef <br/>
 
|-
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xf0 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xf1 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xf2 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xf3 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xf4 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xf5 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xf6 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xf7 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xf8 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xf9 <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | - <br/> 0xfa <br/>
 
| style="border:1px solid #aaaaaa; background-color:#f0f0f0;" | _SMALLINTEGER <br/> 0xfb <br/>
 
| style="border:1px solid #aaaaaa; background-color:#f0f0f0;" | _PUBKEYS <br/> 0xfc <br/>
 
| style="border:1px solid #aaaaaa; background-color:#f0f0f0;" | _PUBKEYHASH  <br/> 0xfd <br/>
 
| style="border:1px solid #aaaaaa; background-color:#f0f0f0;" | _PUBKEY <br/> 0xfe <br/>
 
| style="border:1px solid #aaaaaa; background-color:#ffffff;" | _INVALIDOPCODE <br/> 0xff <br/>
 
|}<br>
 
Except later pseudo-opcode changes, the definition of OP_NOP1 - OP_NOP10 and the change of the evaluation of OP_RETURN (did no invalidation previously) which both occured in bitcoin version 0.3.6  in July 2010 were the last changes regarding opcodes <ref>[http://mirror.transact.net.au/pub/sourceforge/b/project/bi/bitcoin/Bitcoin/bitcoin-0.2.0/bitcoin-0.2.0-linux.tar.gz file src/srcipt.cpp in bitcoin-0.2.0]</ref> <ref>[http://mirror.transact.net.au/pub/sourceforge/b/project/bi/bitcoin/Bitcoin/bitcoin-0.3.3/bitcoin-0.3.3-linux.tar.gz file src/srcipt.cpp in bitcoin-0.3.3]</ref> <ref>[http://mirror.transact.net.au/pub/sourceforge/b/project/bi/bitcoin/Bitcoin/bitcoin-0.3.6/bitcoin-0.3.6-linux.tar.gz file src/srcipt.cpp in bitcoin-0.3.6]</ref>.
 
  
== Opcode descriptions ==
+
== Words ==
It follows for each opcode less than decimal 185 (hexa 0xba) a description for its usage. The columns entitled ''nemonic'', ''decimal'' and ''Hex'' should be evident. The column ''input'' gives the needed items of the stack (and the alternate stack) and the column ''output'' indicates the resulting items on the stack (and the alternate stack). '''Stack-top is always the right most item.''' The naming of the entries in these two columns is chosen to reflect their interpretation. ''x'', ''x0'', ''x1'', ... means arbitrary or no interpretation, ''i0'', ''i1'' and ''i2'' a signed integer value, ''n'',''index'',''size'' and ''depth'' non-negative (unsigned) integer values, ''Boolean'' as either a true or false.<br>
+
This is a list of all Script words (commands/functions). Some of the more complicated opcodes are disabled out of concern that the client might have a bug in their implementation; if a transaction using such an opcode were to be included in the chain any fix would risk forking the chain.  
  
Some of the more complicated opcodes are disabled since version 0.3.10 out of concern that the client might have a bug in the current implementation due to the historically not as 2-complement interpretations of the byte vectors as numerical values (the most significant byte holds the sign of the byte vectors). Furthermore how some of theses opcodes should work precisely is disputable.
+
True=1 and False=0.
  
=== Push data from instruction onto stack ===
+
=== Constants ===
 +
When talking about scripts, these value-pushing words are usually omitted.
  
 
{| class="wikitable"
 
{| class="wikitable"
 
|-
 
|-
!Nemonic
+
!Word
!Decimal
+
!Opcode
 
!Hex
 
!Hex
 
!Input
 
!Input
Line 341: Line 30:
 
!Description
 
!Description
 
|-
 
|-
|OP_FALSE, OP_0
+
|OP_0, OP_FALSE
 
|0
 
|0
 
|0x00
 
|0x00
|Nothing
+
|Nothing.
|Empty string
+
|(empty value)
|A byte vector of length 0 is pushed onto the stack. (Thus, it is not a no-op!)
+
|An empty array of bytes is pushed onto the stack. (This is not a no-op: an item is added to the stack.)
 
|-
 
|-
|(no official nemonics)
+
|N/A
|1 - 75
+
|1-75
|0x01 - 0x4b
+
|0x01-0x4b
|(operand)
+
|(special)
|x
+
|data
|The next <opcode>-many bytes are to be pushed onto the stack.
+
|The next ''opcode'' bytes is data to be pushed onto the stack
 
|-
 
|-
 
|OP_PUSHDATA1
 
|OP_PUSHDATA1
 
|76
 
|76
 
|0x4c
 
|0x4c
|(operands)
+
|(special)
|x
+
|data
|The next byte contains the number of bytes to be pushed onto the stack which follow this byte.
+
|The next byte contains the number of bytes to be pushed onto the stack.
 
|-
 
|-
 
|OP_PUSHDATA2
 
|OP_PUSHDATA2
 
|77
 
|77
 
|0x4d
 
|0x4d
|(operands)
+
|(special)
|x
+
|data
|The next two bytes contain the number of bytes to be pushed onto the stack which follow theses 2 bytes.
+
|The next two bytes contain the number of bytes to be pushed onto the stack.
 
|-
 
|-
 
|OP_PUSHDATA4
 
|OP_PUSHDATA4
 
|78
 
|78
 
|0x4e
 
|0x4e
|(operands)
+
|(special)
|x
+
|data
|The next four bytes contain the number of bytes to be pushed onto the stack which follow theses 4 bytes.
+
|The next four bytes contain the number of bytes to be pushed onto the stack.
 
|-
 
|-
 
|OP_1NEGATE
 
|OP_1NEGATE
 
|79
 
|79
 
|0x4f
 
|0x4f
|Nothing
+
|Nothing.
 
| -1
 
| -1
|The byte with value -1 is pushed onto the stack.
+
|The number -1 is pushed onto the stack.
 
|-
 
|-
 
|OP_1, OP_TRUE
 
|OP_1, OP_TRUE
 
|81
 
|81
 
|0x51
 
|0x51
|Nothing
+
|Nothing.
 
|1
 
|1
|The byte with value 1 is pushed onto the stack.
+
|The number 1 is pushed onto the stack.
 
|-
 
|-
|OP_2 - OP_16
+
|OP_2-OP_16
|82 - 96
+
|82-96
|0x52 - 0x60
+
|0x52-0x60
|Nothing
+
|Nothing.
 
|2-16
 
|2-16
|The byte with value <opcode>-80 (thus, one of 2 - 16) is pushed onto the stack.
+
|The number in the word name (2-16) is pushed onto the stack.
 
|}
 
|}
  
Line 402: Line 91:
 
{| class="wikitable"
 
{| class="wikitable"
 
|-
 
|-
!Nemonic
+
!Word
!Decimal
+
!Opcode
 
!Hex
 
!Hex
 
!Input
 
!Input
Line 419: Line 108:
 
|99
 
|99
 
|0x63
 
|0x63
|Boolean
+
| colspan="2"|<expression> if [statements] [else [statements]]* endif
|Nothing
+
|If the top stack value is not 0, the statements are executed. The top stack value is removed.
|If the top stack value is not 0, the statements are executed. The top stack value is removed. Lead in a logcial ''<value> then [statements] [else [statements]] endif'' expression
 
 
|-
 
|-
 
|OP_NOTIF
 
|OP_NOTIF
 
|100
 
|100
 
|0x64
 
|0x64
|Boolean
+
| colspan="2"|<expression> if [statements] [else [statements]]* endif
|Nothing
+
|If the top stack value is 0, the statements are executed. The top stack value is removed.
|If the top stack value is 0, the statements are executed. The top stack value is removed. Lead in a logcial ''<value> then [statements] [else [statements]] endif'' expression
 
 
|-
 
|-
 
|OP_ELSE
 
|OP_ELSE
 
|103
 
|103
 
|0x67
 
|0x67
|Nothing
+
| colspan="2"|<expression> if [statements] [else [statements]]* endif
|Nothing
+
|If the preceding OP_IF or OP_NOTIF or OP_ELSE was not executed then these statements are and if the preceding OP_IF or OP_NOTIF or OP_ELSE was executed then these statements are not.  
|If the preceeding OP_IF or OP_NOTIF or OP_ELSE was not executed then these statements are and if the preceding OP_IF or OP_NOTIF or OP_ELSE was executed then these statements are not.  
 
 
|-
 
|-
 
|OP_ENDIF
 
|OP_ENDIF
 
|104
 
|104
 
|0x68
 
|0x68
|Nothing
+
| colspan="2"|<expression> if [statements] [else [statements]]* endif
|Nothing
+
|Ends an if/else block.
|Ends a logcial ''If <value> then [statements] [else [statements]] '' expression
 
 
|-
 
|-
 
|OP_VERIFY
 
|OP_VERIFY
 
|105
 
|105
 
|0x69
 
|0x69
|Boolean
+
|True / false
 
|Nothing / False
 
|Nothing / False
|If top stack value is not true then marks transaction as '''invalid''' . A value true is removed, but false is not.
+
|'''Marks transaction as invalid''' if top stack value is not true. True is removed, but false is not.
 
|-
 
|-
 
|OP_RETURN
 
|OP_RETURN
Line 456: Line 141:
 
|Nothing
 
|Nothing
 
|Nothing
 
|Nothing
|Marks transaction as '''invalid'''.  
+
|'''Marks transaction as invalid'''.  
 
|}
 
|}
  
===Stack item organization===
+
=== Stack ===
  
 
{| class="wikitable"  
 
{| class="wikitable"  
 
|-
 
|-
!Nemonic
+
!Word
!Decimal
+
!Opcode
 
!Hex
 
!Hex
 
!Input
 
!Input
Line 473: Line 158:
 
|107
 
|107
 
|0x6b
 
|0x6b
|x1 (alt)
+
|x1
|(alt x1)
+
|(alt)x1
|Puts the input onto the top of the alt stack. Removes it from the (main) stack.
+
|Puts the input onto the top of the alt stack. Removes it from the main stack.
 
|-
 
|-
 
|OP_FROMALTSTACK
 
|OP_FROMALTSTACK
 
|108
 
|108
 
|0x6c
 
|0x6c
|(alt x1)
+
|(alt)x1
|x1 (alt)
+
|x1
|Puts the input onto the top of the (main) stack. Removes it from the alt stack.
+
|Puts the input onto the top of the main stack. Removes it from the alt stack.
|-
 
|OP_2DROP
 
|109
 
|0x6d
 
|x2 x1
 
|Nothing
 
|Removes the top two stack items.
 
|-
 
|OP_2DUP
 
|110
 
|0x6e
 
|x2 x1
 
|x2 x1 x2 x1
 
|Duplicates the top two stack items.
 
|-
 
|OP_3DUP
 
|111
 
|0x6f
 
|x3 x2 x1
 
|x3 x2 x1 x3 x2 x1
 
|Duplicates the top three stack items.
 
|-
 
|OP_2OVER
 
|112
 
|0x70
 
|x4 x3 x2 x1
 
|x4 x3 x2 x1 x4 x3
 
|Copies the pair of items two spaces back in the stack to the front.
 
|-
 
|OP_2ROT
 
|113
 
|0x71
 
|x6 x5 x4 x3 x2 x1
 
|x4 x3 x2 x1 x6 x5
 
|The fifth and sixth items back are moved to the top of the stack. Twotimes left rotate.
 
|-
 
|OP_2SWAP
 
|114
 
|0x72
 
|x4 x3 x2 x1
 
|x2 x1 x4 x3
 
|Swaps the top two pairs of stack items.
 
 
|-
 
|-
 
|OP_IFDUP
 
|OP_IFDUP
 
|115
 
|115
 
|0x73
 
|0x73
|x1
+
|x
|x1 / x1 x1
+
|x / x x
 
|If the top stack value is not 0, duplicate it.
 
|If the top stack value is not 0, duplicate it.
 
|-
 
|-
Line 537: Line 180:
 
|0x74
 
|0x74
 
|Nothing
 
|Nothing
|depth
+
|<Stack size>
|Puts the number of stack items onto the stack as one little-endian coded byte-vector
+
|Puts the number of stack items onto the stack.
 
|-
 
|-
 
|OP_DROP
 
|OP_DROP
 
|117
 
|117
 
|0x75
 
|0x75
|x1
+
|x
 
|Nothing
 
|Nothing
 
|Removes the top stack item.
 
|Removes the top stack item.
Line 550: Line 193:
 
|118
 
|118
 
|0x76
 
|0x76
|x1
+
|x
|x1 x1
+
|x x
 
|Duplicates the top stack item.
 
|Duplicates the top stack item.
 
|-
 
|-
Line 557: Line 200:
 
|119
 
|119
 
|0x77
 
|0x77
|x2 x1
+
|x1 x2
|x1
+
|x2
 
|Removes the second-to-top stack item.
 
|Removes the second-to-top stack item.
 
|-
 
|-
Line 564: Line 207:
 
|120
 
|120
 
|0x78
 
|0x78
|x2 x1
+
|x1 x2
|x2 x1 x2
+
|x1 x2 x1
 
|Copies the second-to-top stack item to the top.
 
|Copies the second-to-top stack item to the top.
 
|-
 
|-
Line 573: Line 216:
 
|xn ... x2 x1 x0 <n>
 
|xn ... x2 x1 x0 <n>
 
|xn ... x2 x1 x0 xn
 
|xn ... x2 x1 x0 xn
|<n> is removed and the item ''n'' back in the stack is copied to the top.
+
|The item ''n'' back in the stack is copied to the top.
 
|-
 
|-
 
|OP_ROLL
 
|OP_ROLL
Line 580: Line 223:
 
|xn ... x2 x1 x0 <n>
 
|xn ... x2 x1 x0 <n>
 
|... x2 x1 x0 xn
 
|... x2 x1 x0 xn
|<n> is removed and the item ''n'' back in the stack is moved to the top.
+
|The item ''n'' back in the stack is moved to the top.
 
|-
 
|-
 
|OP_ROT
 
|OP_ROT
 
|123
 
|123
 
|0x7b
 
|0x7b
|x3 x2 x1
+
|x1 x2 x3
|x2 x1 x3
+
|x2 x3 x1
 
|The top three items on the stack are rotated to the left.
 
|The top three items on the stack are rotated to the left.
 
|-
 
|-
Line 592: Line 235:
 
|124
 
|124
 
|0x7c
 
|0x7c
 +
|x1 x2
 
|x2 x1
 
|x2 x1
|x1 x2
+
|The top two items on the stack are swapped.
|The top two items on the stack are swapped resp. rotated.
 
 
|-
 
|-
 
|OP_TUCK
 
|OP_TUCK
 
|125
 
|125
 
|0x7d
 
|0x7d
|x2 x1
+
|x1 x2
|x1 x2 x1
+
|x2 x1 x2
 
|The item at the top of the stack is copied and inserted before the second-to-top item.
 
|The item at the top of the stack is copied and inserted before the second-to-top item.
 +
|-
 +
|OP_2DROP
 +
|109
 +
|0x6d
 +
|x1 x2
 +
|Nothing
 +
|Removes the top two stack items.
 +
|-
 +
|OP_2DUP
 +
|110
 +
|0x6e
 +
|x1 x2
 +
|x1 x2 x1 x2
 +
|Duplicates the top two stack items.
 +
|-
 +
|OP_3DUP
 +
|111
 +
|0x6f
 +
|x1 x2 x3
 +
|x1 x2 x3 x1 x2 x3
 +
|Duplicates the top three stack items.
 +
|-
 +
|OP_2OVER
 +
|112
 +
|0x70
 +
|x1 x2 x3 x4
 +
|x1 x2 x3 x4 x1 x2
 +
|Copies the pair of items two spaces back in the stack to the front.
 +
|-
 +
|OP_2ROT
 +
|113
 +
|0x71
 +
|x1 x2 x3 x4 x5 x6
 +
|x3 x4 x5 x6 x1 x2
 +
|The fifth and sixth items back are moved to the top of the stack.
 +
|-
 +
|OP_2SWAP
 +
|114
 +
|0x72
 +
|x1 x2 x3 x4
 +
|x3 x4 x1 x2
 +
|Swaps the top two pairs of items.
 
|}
 
|}
  
Line 608: Line 293:
 
{| class="wikitable"  
 
{| class="wikitable"  
 
|-
 
|-
!Nemonic
+
!Word
!Decimal
+
!Opcode
 
!Hex
 
!Hex
 
!Input
 
!Input
Line 618: Line 303:
 
|126
 
|126
 
|0x7e
 
|0x7e
|x2 x1
+
|x1 x2
 
|out
 
|out
|Appends stack-top item at second-to top item. Concatenates two strings resp. byte vectors. ''Currently disabled.''
+
|Concatenates two strings. ''Currently disabled.''
 
|-
 
|-
 
|OP_SUBSTR
 
|OP_SUBSTR
 
|127
 
|127
 
|0x7f
 
|0x7f
|x3 index size
+
|in begin size
 
|out
 
|out
|Returns the section started at position <index> and of length <size> of a string resp. byte vector. ''Currently disabled.''
+
|Returns a section of a string. ''Currently disabled.''
 
|-
 
|-
 
|OP_LEFT
 
|OP_LEFT
 
|128
 
|128
 
|0x80
 
|0x80
|x2 index
+
|in size
 
|out
 
|out
|Keeps only characters left of the specified point in second-to top item. ''Currently disabled.''
+
|Keeps only characters left of the specified point in a string. ''Currently disabled.''
 
|-
 
|-
 
|OP_RIGHT
 
|OP_RIGHT
 
|129
 
|129
 
|0x81
 
|0x81
|x2 index
+
|in size
 
|out
 
|out
|Keeps only characters right of the specified point in second-to top item. ''Currently disabled.''
+
|Keeps only characters right of the specified point in a string. ''Currently disabled.''
 
|-
 
|-
 
|OP_SIZE
 
|OP_SIZE
 
|130
 
|130
 
|0x82
 
|0x82
|x1
+
|in
|x1 size
+
|in size
|Returns the length of the input string resp. byte vector resp. top-stack item.
+
|Returns the length of the input string.
 
|}
 
|}
  
Line 655: Line 340:
 
{| class="wikitable"  
 
{| class="wikitable"  
 
|-
 
|-
!Nemonic
+
!Word
!Decimal
+
!Opcode
 
!Hex
 
!Hex
 
!Input
 
!Input
Line 665: Line 350:
 
|131
 
|131
 
|0x83
 
|0x83
|x1
+
|in
|x0
+
|out
 
|Flips all of the bits in the input. ''Currently disabled.''
 
|Flips all of the bits in the input. ''Currently disabled.''
 
|-
 
|-
Line 672: Line 357:
 
|132
 
|132
 
|0x84
 
|0x84
|x2 x1
+
|x1 x2
|x0
+
|out
 
|Boolean ''and'' between each bit in the inputs. ''Currently disabled.''
 
|Boolean ''and'' between each bit in the inputs. ''Currently disabled.''
 
|-
 
|-
Line 679: Line 364:
 
|133
 
|133
 
|0x85
 
|0x85
|x2 x1
+
|x1 x2
|x0
+
|out
 
|Boolean ''or'' between each bit in the inputs. ''Currently disabled.''
 
|Boolean ''or'' between each bit in the inputs. ''Currently disabled.''
 
|-
 
|-
Line 686: Line 371:
 
|134
 
|134
 
|0x86
 
|0x86
|x2 x1
+
|x1 x2
|x0
+
|out
 
|Boolean ''exclusive or'' between each bit in the inputs. ''Currently disabled.''
 
|Boolean ''exclusive or'' between each bit in the inputs. ''Currently disabled.''
 
|-
 
|-
Line 693: Line 378:
 
|135
 
|135
 
|0x87
 
|0x87
|x2 x1
+
|x1 x2
|Boolean
+
|True / false
|Returns 1 if the inputs have the same length and are byte-wise equal, 0 otherwise.
+
|Returns 1 if the inputs are exactly equal, 0 otherwise.
 
|-
 
|-
 
|OP_EQUALVERIFY
 
|OP_EQUALVERIFY
 
|136
 
|136
 
|0x88
 
|0x88
|x2 x1
+
|x1 x2
|Nothing / false
+
|True / false
 
|Same as OP_EQUAL, but runs OP_VERIFY afterward.
 
|Same as OP_EQUAL, but runs OP_VERIFY afterward.
 
|}
 
|}
Line 707: Line 392:
 
=== Arithmetic ===
 
=== Arithmetic ===
  
Since version 0.3.10 the implemented arithmetic opcodes are limited to maximal 4 byte vectors (|value| < 2^31), in version 0.3.6 up to 0.3.8 they were limited to 258 byte vectors and prior to 0.3.6 unrestricted <ref>[http://mirror.transact.net.au/pub/sourceforge/b/project/bi/bitcoin/Bitcoin/bitcoin-0.3.8/bitcoin-0.3.8-linux.tar.gz file src/srcipt.cpp in bitcoin-0.3.8]</ref><ref>[http://mirror.transact.net.au/pub/sourceforge/b/project/bi/bitcoin/Bitcoin/bitcoin-0.3.10/bitcoin-0.3.10-linux.tar.gz file src/srcipt.cpp in bitcoin-0.3.10]</ref>.
+
Arithmetic is limited to max 4 byte integers
 +
 
 
{| class="wikitable"  
 
{| class="wikitable"  
 
|-
 
|-
!Nemonic
+
!Word
!Decimal
+
!Opcode
 
!Hex
 
!Hex
 
!Input
 
!Input
Line 720: Line 406:
 
|139
 
|139
 
|0x8b
 
|0x8b
|i1
+
|in
|i0
+
|out
 
|1 is added to the input.
 
|1 is added to the input.
 
|-
 
|-
Line 727: Line 413:
 
|140
 
|140
 
|0x8c
 
|0x8c
|i1
+
|in
|i0
+
|out
 
|1 is subtracted from the input.
 
|1 is subtracted from the input.
 
|-
 
|-
Line 734: Line 420:
 
|141
 
|141
 
|0x8d
 
|0x8d
|i1
+
|in
|i0
+
|out
 
|The input is multiplied by 2. ''Currently disabled.''
 
|The input is multiplied by 2. ''Currently disabled.''
 
|-
 
|-
Line 741: Line 427:
 
|142
 
|142
 
|0x8e
 
|0x8e
|i1
+
|in
|i0
+
|out
|The input is divided by 2 (round down). ''Currently disabled.''
+
|The input is divided by 2. ''Currently disabled.''
 
|-
 
|-
 
|OP_NEGATE
 
|OP_NEGATE
 
|143
 
|143
 
|0x8f
 
|0x8f
|i1
+
|in
|i0
+
|out
|The sign of the input is flipped. Numerically the value is multiplied by -1
+
|The sign of the input is flipped.
 
|-
 
|-
 
|OP_ABS
 
|OP_ABS
 
|144
 
|144
 
|0x90
 
|0x90
|i1
+
|in
|i0
+
|out
|The input is negative, its sign is flipped.
+
|The input is made positive.
 
|-
 
|-
 
|OP_NOT
 
|OP_NOT
 
|145
 
|145
 
|0x91
 
|0x91
|i1
+
|in
|Boolean
+
|out
|If the input is 0 or 1, it is flipped. Otherwise the output will be 0. Test whether its value equals 0
+
|If the input is 0 or 1, it is flipped. Otherwise the output will be 0.
 
|-
 
|-
 
|OP_0NOTEQUAL
 
|OP_0NOTEQUAL
 
|146
 
|146
 
|0x92
 
|0x92
|i1
+
|in
|Boolean
+
|out
|Returns 0 if the input is 0. 1 otherwise. Test whether its value is unequal 0
+
|Returns 0 if the input is 0. 1 otherwise.
 
|-
 
|-
 
|OP_ADD
 
|OP_ADD
 
|147
 
|147
 
|0x93
 
|0x93
|i2 i1
+
|a b
|i0
+
|out
|stack-top i1 is added to i2.
+
|a is added to b.
 
|-
 
|-
 
|OP_SUB
 
|OP_SUB
 
|148
 
|148
 
|0x94
 
|0x94
|i2 i1
+
|a b
|i0
+
|out
|stack-top i1 is subtracted from i2.
+
|b is subtracted from a.
 
|-
 
|-
 
|OP_MUL
 
|OP_MUL
 
|149
 
|149
 
|0x95
 
|0x95
|i2 i1
+
|a b
|i0
+
|out
|i2 is multiplied with stack-top i1. ''Currently disabled.''
+
|a is multiplied by b. ''Currently disabled.''
 
|-
 
|-
 
|OP_DIV
 
|OP_DIV
 
|150
 
|150
 
|0x96
 
|0x96
|i2 i1
+
|a b
|i0
+
|out
|i2 is divided by stack-top i1 (divisor should be not 0). ''Currently disabled.''
+
|a is divided by b. ''Currently disabled.''
 
|-
 
|-
 
|OP_MOD
 
|OP_MOD
 
|151
 
|151
 
|0x97
 
|0x97
|i2 i1
+
|a b
|i0
+
|out
|Returns the remainder after dividing i2 by stack-top i1 (divisor should be not 0). ''Currently disabled.''
+
|Returns the remainder after dividing a by b. ''Currently disabled.''
 
|-
 
|-
 
|OP_LSHIFT
 
|OP_LSHIFT
 
|152
 
|152
 
|0x98
 
|0x98
|i2 i1
+
|a b
|i0
+
|out
|Shifts i2 left by i1 bits, preserving sign of i2 (i1 >= 0). ''Currently disabled.''
+
|Shifts a left b bits, preserving sign. ''Currently disabled.''
 
|-
 
|-
 
|OP_RSHIFT
 
|OP_RSHIFT
 
|153
 
|153
 
|0x99
 
|0x99
|i2 i1
+
|a b
|i0
+
|out
|Shifts i2 right by i1 bits, preserving sign of i2 (i1 >= 0). ''Currently disabled.''
+
|Shifts a right b bits, preserving sign. ''Currently disabled.''
 
|-
 
|-
 
|OP_BOOLAND
 
|OP_BOOLAND
 
|154
 
|154
 
|0x9a
 
|0x9a
|i2 i1
+
|a b
|Boolean
+
|out
|If both i2 and i1 are not 0, the output is 1. Otherwise 0.
+
|If both a and b are not 0, the output is 1. Otherwise 0.
 
|-
 
|-
 
|OP_BOOLOR
 
|OP_BOOLOR
 
|155
 
|155
 
|0x9b
 
|0x9b
|i2 i1
+
|a b
|Boolean
+
|out
|If i2 or i1 is not 0, the output is 1. Otherwise 0.
+
|If a or b is not 0, the output is 1. Otherwise 0.
 
|-
 
|-
 
|OP_NUMEQUAL
 
|OP_NUMEQUAL
 
|156
 
|156
 
|0x9c
 
|0x9c
|i2 i1
+
|a b
|Boolean
+
|out
|Returns 1 if i2 and i1 are numerically equal, 0 otherwise.
+
|Returns 1 if the numbers are equal, 0 otherwise.
 
|-
 
|-
 
|OP_NUMEQUALVERIFY
 
|OP_NUMEQUALVERIFY
 
|157
 
|157
 
|0x9d
 
|0x9d
|i2 i1
+
|a b
|Nothing / False
+
|out
 
|Same as OP_NUMEQUAL, but runs OP_VERIFY afterward.
 
|Same as OP_NUMEQUAL, but runs OP_VERIFY afterward.
 
|-
 
|-
Line 853: Line 539:
 
|158
 
|158
 
|0x9e
 
|0x9e
|i2 i1
+
|a b
|Boolean
+
|out
|Returns 1 if i2 and i1 are numerically not equal, 0 otherwise.
+
|Returns 1 if the numbers are not equal, 0 otherwise.
 
|-
 
|-
 
|OP_LESSTHAN
 
|OP_LESSTHAN
 
|159
 
|159
 
|0x9f
 
|0x9f
|i2 i1
+
|a b
|Boolean
+
|out
|Returns 1 if i2 is less than stack-top item i1, 0 otherwise.
+
|Returns 1 if a is less than b, 0 otherwise.
 
|-
 
|-
 
|OP_GREATERTHAN
 
|OP_GREATERTHAN
 
|160
 
|160
 
|0xa0
 
|0xa0
|i2 i1
+
|a b
|Boolean
+
|out
|Returns 1 if i2 is greater than stack-top item i1, 0 otherwise.
+
|Returns 1 if a is greater than b, 0 otherwise.
 
|-
 
|-
 
|OP_LESSTHANOREQUAL
 
|OP_LESSTHANOREQUAL
 
|161
 
|161
 
|0xa1
 
|0xa1
|i2 i1
+
|a b
|Boolean
+
|out
|Returns 1 if i2 is less than or equal to stack-top item i1, 0 otherwise.
+
|Returns 1 if a is less than or equal to b, 0 otherwise.
 
|-
 
|-
 
|OP_GREATERTHANOREQUAL
 
|OP_GREATERTHANOREQUAL
 
|162
 
|162
 
|0xa2
 
|0xa2
|i2 i1
+
|a b
|Boolean
+
|out
|Returns 1 if i2 is greater than or equal to stack-top item i1, 0 otherwise.
+
|Returns 1 if a is greater than or equal to b, 0 otherwise.
 
|-
 
|-
 
|OP_MIN
 
|OP_MIN
 
|163
 
|163
 
|0xa3
 
|0xa3
|i2 i1
+
|a b
|i2 / i1
+
|out
|Returns the smaller of i2 and i1.
+
|Returns the smaller of a and b.
 
|-
 
|-
 
|OP_MAX
 
|OP_MAX
 
|164
 
|164
 
|0xa4
 
|0xa4
|i2 i1
+
|a b
|i2 / i1
+
|out
|Returns the larger of i2 and i1.
+
|Returns the larger of a and b.
 
|-
 
|-
 
|OP_WITHIN
 
|OP_WITHIN
 
|165
 
|165
 
|0xa5
 
|0xa5
|i3 i2 i1
+
|x min max
|Boolean
+
|out
|Returns 1 if i3  >= i2 and i3 < i1, 0 otherwise. Thus if i2 > i1 returns always 0.
+
|Returns 1 if x is within the specified range (left-inclusive), 0 otherwise.
 
|}
 
|}
  
Line 911: Line 597:
 
{| class="wikitable"  
 
{| class="wikitable"  
 
|-
 
|-
!Nemonic
+
!Word
!Decimal
+
!Opcode
 
!Hex
 
!Hex
 
!Input
 
!Input
Line 921: Line 607:
 
|166
 
|166
 
|0xa6
 
|0xa6
|x
+
|in
|hash20
+
|hash
 
|The input is hashed using RIPEMD-160.
 
|The input is hashed using RIPEMD-160.
 
|-
 
|-
Line 928: Line 614:
 
|167
 
|167
 
|0xa7
 
|0xa7
|x
+
|in
|hash20
+
|hash
 
|The input is hashed using SHA-1.
 
|The input is hashed using SHA-1.
 
|-
 
|-
Line 935: Line 621:
 
|168
 
|168
 
|0xa8
 
|0xa8
|x
+
|in
|hash32
+
|hash
 
|The input is hashed using SHA-256.
 
|The input is hashed using SHA-256.
 
|-
 
|-
Line 942: Line 628:
 
|169
 
|169
 
|0xa9
 
|0xa9
|x
+
|in
|hash20
+
|hash
 
|The input is hashed twice: first with SHA-256 and then with RIPEMD-160.
 
|The input is hashed twice: first with SHA-256 and then with RIPEMD-160.
 
|-
 
|-
Line 949: Line 635:
 
|170
 
|170
 
|0xaa
 
|0xaa
|x
+
|in
|hash32
+
|hash
 
|The input is hashed two times with SHA-256.
 
|The input is hashed two times with SHA-256.
 
|-
 
|-
Line 958: Line 644:
 
|Nothing
 
|Nothing
 
|Nothing
 
|Nothing
|All of the signature checking opcodes will only match signatures to the data after the most recently-executed OP_CODESEPARATOR.
+
|All of the signature checking words will only match signatures to the data after the most recently-executed OP_CODESEPARATOR.
 
|-
 
|-
 
|[[OP_CHECKSIG]]
 
|[[OP_CHECKSIG]]
Line 964: Line 650:
 
|0xac
 
|0xac
 
|sig pubkey
 
|sig pubkey
|Boolean
+
|True / false
|The entire transaction's outputs, inputs, and script (from the most recently-executed OP_CODESEPARATOR to the end) are hashed. The signature used by OP_CHECKSIG must be a valid signature for a further, extern specified hash and the given public key. If it is, 1 is returned, 0 otherwise.
+
|The entire transaction's outputs, inputs, and script (from the most recently-executed OP_CODESEPARATOR to the end) are hashed. The signature used by OP_CHECKSIG must be a valid signature for this hash and public key. If it is, 1 is returned, 0 otherwise.
 
|-
 
|-
 
|OP_CHECKSIGVERIFY
 
|OP_CHECKSIGVERIFY
Line 971: Line 657:
 
|0xad
 
|0xad
 
|sig pubkey
 
|sig pubkey
|Nothing / False
+
|True / false
 
|Same as OP_CHECKSIG, but OP_VERIFY is executed afterward.
 
|Same as OP_CHECKSIG, but OP_VERIFY is executed afterward.
 
|-
 
|-
Line 977: Line 663:
 
|174
 
|174
 
|0xae
 
|0xae
|sig1 sig2 ... <number of signatures> pub1 pub2 <number of public keys>
+
|x sig1 sig2 ... <number of signatures> pub1 pub2 <number of public keys>
|Boolean
+
|True / False
 
|For each signature and public key pair, OP_CHECKSIG is executed. If more public keys than signatures are listed, some key/sig pairs can fail. All signatures need to match a public key. If all signatures are valid, 1 is returned, 0 otherwise. Due to a bug, one extra unused value is removed from the stack.
 
|For each signature and public key pair, OP_CHECKSIG is executed. If more public keys than signatures are listed, some key/sig pairs can fail. All signatures need to match a public key. If all signatures are valid, 1 is returned, 0 otherwise. Due to a bug, one extra unused value is removed from the stack.
 
|-
 
|-
Line 984: Line 670:
 
|175
 
|175
 
|0xaf
 
|0xaf
|sig1 sig2 ... <number of signatures> pub1 pub2 ... <number of public keys>
+
|x sig1 sig2 ... <number of signatures> pub1 pub2 ... <number of public keys>
|Nothing / False
+
|True / False
 
|Same as OP_CHECKMULTISIG, but OP_VERIFY is executed afterward.
 
|Same as OP_CHECKMULTISIG, but OP_VERIFY is executed afterward.
 
|}
 
|}
  
=== Expansion opcodes ===
+
===Pseudo-words===
{| class="wikitable"
+
These words are used internally for assisting with transaction matching. They are invalid if used in actual scripts.
 +
{| class="wikitable"  
 
|-
 
|-
!Nemonic
+
!Word
!Decimal
+
!Opcode
 
!Hex
 
!Hex
 
!Description
 
!Description
 
|-
 
|-
|OP_NOP1-OP_NOP10
+
|OP_PUBKEYHASH
|176-185
+
|253
|0xb0-0xb9
+
|0xfd
|The opcode has no effect.
+
|Represents a public key hashed with OP_HASH160.
 +
|-
 +
|OP_PUBKEY
 +
|254
 +
|0xfe
 +
|Represents a public key compatible with OP_CHECKSIG.
 +
|-
 +
|OP_INVALIDOPCODE
 +
|255
 +
|0xff
 +
|Matches any opcode that is not yet assigned.
 
|}
 
|}
  
=== Version opcodes ===
+
=== Reserved words ===
Version opcodes are disabled since bitcoin 0.2.0 and should not be used (maybe reassigned in the future).
+
Any opcode not assigned is also reserved. Using an unassigned opcode makes the transaction invalid.
 +
 
 
{| class="wikitable"  
 
{| class="wikitable"  
 
|-
 
|-
!Nemonic
+
!Word
!Decimal
+
!Opcode
 
!Hex
 
!Hex
!Description
+
!When used...
 +
|-
 +
|OP_RESERVED
 +
|80
 +
|0x50
 +
|Transaction is invalid unless occuring in an unexecuted OP_IF branch
 
|-
 
|-
 
|OP_VER
 
|OP_VER
 
|98
 
|98
 
|0x62
 
|0x62
|Script evalution is triggered invalid (Formerly pushed the bitcoin-serialize version onto stack).
+
|Transaction is invalid unless occuring in an unexecuted OP_IF branch
 
|-
 
|-
 
|OP_VERIF
 
|OP_VERIF
 
|101
 
|101
 
|0x65
 
|0x65
|Script evalution is triggered invalid (Formerly top stack item was popped and =< compared to present version)
+
|Transaction is invalid even when occuring in an unexecuted OP_IF branch
 
|-
 
|-
 
|OP_VERNOTIF
 
|OP_VERNOTIF
 
|102
 
|102
 
|0x66
 
|0x66
|Script evalution is triggered invalid (Formerly top stack item was popped and > compared to present version)
+
|Transaction is invalid even when occuring in an unexecuted OP_IF branch
|}
 
 
 
=== Reserved opcodes ===
 
Each opcode not assigned (currently also every opcode value > 185) is also reserved. Using any unassigned opcode triggers the script evaluation to be invalid.
 
{| class="wikitable"
 
|-
 
!Nemonic
 
!Decimal
 
!Hex
 
!Description
 
|-
 
|OP_RESERVED
 
|80
 
|0x50
 
|Script evalution is triggered invalid-
 
 
|-
 
|-
 
|OP_RESERVED1
 
|OP_RESERVED1
 
|137
 
|137
 
|0x89
 
|0x89
|Script evalution is triggered invalid.
+
|Transaction is invalid unless occuring in an unexecuted OP_IF branch
 
|-
 
|-
 
|OP_RESERVED2
 
|OP_RESERVED2
 
|138
 
|138
 
|0x8a
 
|0x8a
|Script evalution is triggered invalid.
+
|Transaction is invalid unless occuring in an unexecuted OP_IF branch
|}
 
 
 
===Pseudo-opcodes===
 
These nemonics are used internally for assisting with transaction matching. They are invalid if used in actual scripts.
 
{| class="wikitable"
 
 
|-
 
|-
!Nemonic
+
|OP_NOP1-OP_NOP10
!Decimal
+
|176-185
!Hex
+
|0xb0-0xb9
!Description
+
|The word is ignored.
|-
 
|OP_PUBKEYHASH
 
|253
 
|0xfd
 
|Represents a public key hashed with OP_HASH160.
 
|-
 
|OP_PUBKEY
 
|254
 
|0xfe
 
|Represents a public key compatible with OP_CHECKSIG.
 
|-
 
|OP_INVALIDOPCODE
 
|255
 
|0xff
 
|Matches any opcode that is not yet assigned.
 
 
|}
 
|}
  
==Scripts in bitcoin transactions==
+
== Scripts ==
It follows a list of important (most occuring) scripts to see opcodes "at work". Keep in mind that all constants actually use the data-pushing instructions above. At start of a (transaction input) script evaluation, the stack is always empty. Currently less than 0.01 % of all txout-scripts / scriptPubKeys in the main block chain are not of the following two standard scripts.
+
This is a list of interesting scripts. Keep in mind that all constants actually use the data-pushing commands above.
  
===Standard transaction to bitcoin address===
+
=== Standard Transaction to Bitcoin address ===
  
 
  scriptPubKey: OP_DUP OP_HASH160 <pubKeyHash> OP_EQUALVERIFY OP_CHECKSIG
 
  scriptPubKey: OP_DUP OP_HASH160 <pubKeyHash> OP_EQUALVERIFY OP_CHECKSIG
Line 1,093: Line 761:
 
                       Data to push                    OP_EQUALVERIFY OP_CHECKSIG</pre>
 
                       Data to push                    OP_EQUALVERIFY OP_CHECKSIG</pre>
  
Note: scriptSig is in the input of the spending transaction and scriptPubKey is in the output of the previously storing transaction, i.e. its "available bitcoins".
+
Note: scriptSig is in the input of the spending transaction and scriptPubKey is in the output of the previously unspent i.e. "available" transaction.
  
Here is how each instruction is processed:
+
Here is how each word is processed:
 
{| class="wikitable"  
 
{| class="wikitable"  
 
|-
 
|-
Line 1,131: Line 799:
 
|}
 
|}
  
===Transaction to IP address (and generation transaction)===
+
=== Standard Generation / transaction to IP address ===
  
 
  scriptPubKey: <pubKey> OP_CHECKSIG
 
  scriptPubKey: <pubKey> OP_CHECKSIG
Line 1,156: Line 824:
 
|}
 
|}
  
In the case of a '''coin generation transaction''' (the first transaction of each block), there is no scriptSig, resp. its code ("coinbase") is completly ignored for the transaction. Only the scriptPubKey is used.
+
=== Transaction with a message ===
  
===Transaction with a message===
+
It's possible to add arbitrary data to any transaction by just adding some data along with OP_DROP. Scripts are limited to 10,000 bytes and 201 instructions, and each individual instruction/value is limited to 520 bytes.
  
It's possible to add arbitrary data to any transaction by just adding some data along with OP_DROP.
 
 
  scriptPubKey: <message> OP_DROP <pubKey> OP_CHECKSIG
 
  scriptPubKey: <message> OP_DROP <pubKey> OP_CHECKSIG
 
  scriptSig: <sig>
 
  scriptSig: <sig>
Line 1,195: Line 862:
 
|}
 
|}
  
===Examples of non standard transaction on Testnet===
+
=== Example non standard transaction on Testnet ===
  
These two links below show a non standard transaction. It just prepends the hex of "bob" and the operation OP_DROP
+
These 2 links below show a non standard transaction. It just prepends the hex of "bob" and the operation OP_DROP
 
which just removes it. As you can see they can be spent as normal.
 
which just removes it. As you can see they can be spent as normal.
  
Line 1,206: Line 873:
 
http://blockexplorer.com/testnet/t/AFdRB1CHS3
 
http://blockexplorer.com/testnet/t/AFdRB1CHS3
  
==Script validation==
+
==See Also==
A script evaluation is considered invalid, if any of these conditions meets:<br>
 
<ul>
 
<li>the total size of the script exceeds (currently) 10000 bytes
 
<li>there are more than (currently) 201 opcodes of opcode value > 0x60 in the script
 
<li>each instruction is (currently) limited to maximal 520 bytes. This effects only the opcodes OP_PUSHDATA2 and OP_PUSHDATA4
 
<li>the executed opcode of the script has insufficient input (from stack, from script or from anywhere)
 
<li>the opcode is not defined (for execution) - indicated by white or light gray background color in the table
 
<li>the opcode is disabled (currently 15 opcodes) - indicated by white font color in the opcode overview matrix
 
<li>stack overflow occurs during execution of the opcode (currently the number of items on the stack and on the alternate stack is limited to 1000)
 
<li>the opcodes OP_VERIF and OP_NOTVERIF invalidate a script which contains this opcode (even if this opcode is not executed!)
 
<li>the opcodes OP_ELSE or OP_ENDIF has no matching OP_IF<br>
 
<li>the script execution has been finished but there is (at least) an unmatched OP_IF<br>
 
<li>the opcodes OP_VERIFY, OP_EQUALVERIFY, OP_NUMEQUALVERIFY, OP_CHECKSIGVERIFY and OP_CHECKMULTISIGVERIFY invalidate the script if the stack-top item is false
 
<li>the execution of OP_RETURN
 
<!--li>alt stack overflow occurs (only possible during execution of OP_TOALTSTACK)-->
 
<li>the numerical value of the top-stack item is negative or greater than the number of items - 2 on the stack if OP_PICK or OP_ROLL shall be executed
 
<li>When interpreting a stack-item of an arithmetic opcode as a signed integer its value is >= 2^31 or <= -2^31.
 
<li>an item used as public key or signature for each of the opcodes OP_CHECKSIG, OP_CHECKSIGVERIFY, OP_CHECKMULTISIG or  OP_CHECKMULTISIGVERIFY can be neither a public key or signature (for the given hash)
 
<li>the number of signature items or the number of public key items on the stack is negative for OP_CHECKMULTISIG or  OP_CHECKMULTISIGVERIFY
 
<li>there or more signatures items than public key items on the stack for OP_CHECKMULTISIG or  OP_CHECKMULTISIGVERIFY
 
<li>there are (currently) more than 20 public key items on the stack for OP_CHECKMULTISIG or CHECKMULTISIGVERIFY
 
<li>the sum of opcodes > 0x60 and the number of public keys in all executed OP_CHECKMULTISIG or CHECKMULTISIGVERIFY exceeds (currently) 201
 
<li>the script execution has been finished and the stack is empty or the top-stack item is false (numerical value 0)
 
</ul>
 
else the script evaluation is considered to be valid.<ref>[http://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-0.7.1/bitcoin-0.7.1-linux.tar.gz file src/src/script.cpp in bitcoin-0.7.1]</ref>
 
'''If invalidation of a script is triggered then the script is immediately finished.''' These arbitrary looking limitations of 10000, 201, 520, 1000 and 20 might be increased in the future -- they serve to prevent strong slow down of the evaluation of a script while not restricting its practical usage really.
 
  
==Withdrawn and drafted opcodes==
 
 
<ul>
 
<li> byte value 0x89 OP_NOTEQUAL  defined in pre-0.1.0 bitcoin versions. Since 0.1.0 removed because of security concerns.
 
<li> byte value 0xb1 [[BIP 0012 | OP_EVAL]]  withdraw - poll was triggered but insufficient support.
 
<li> byte value 0xb2 [[BIP 0017 | OP_CHECKHASHVERIFY]]  withdraw - poll was triggered but insufficient support.
 
</ul>
 
 
==See Also==
 
 
* [[Transactions]]
 
* [[Transactions]]
 
* [[Contracts]]
 
* [[Contracts]]
  
==References==
+
 
<references/>
 
<ul>
 
<li>[http://www.zorinaq.com/pub/bitcoin-0.1.0.tgz file src/script.cpp in bitcoin-0.1.0]</li>
 
</ul>
 
 
[[Category:Technical]]
 
[[Category:Technical]]
 
[[Category:Vocabulary]]
 
[[Category:Vocabulary]]

Revision as of 01:52, 13 January 2013

Bitcoin uses a scripting system for transactions. Forth-like, Script is simple, stack-based, and processed from left to right. It is purposefully not Turing-complete, with no loops.

A script is essentially a list of instructions recorded with each transaction that describe how the next person wanting to spend the Bitcoins being transferred can gain access to them. The script for a typical Bitcoin transfer to destination Bitcoin address D simply encumbers future spending of the bitcoins with two things: the spender must provide

  1. a public key that, when hashed, yields destination address D embedded in the script, and
  2. a signature to show evidence of the private key corresponding to the public key just provided.

Scripting provides the flexibility to change the parameters of what's needed to spend transferred Bitcoins. For example, the scripting system could be used to require two private keys, or a combination of several, or even no keys at all.

A transaction is valid if nothing in the combined script triggers failure and the top stack item is true (non-zero). The party who originally sent the Bitcoins now being spent, dictates the script operations that will occur last in order to release them for use in another transaction. The party wanting to spend them must provide the input(s) to the previously recorded script that results in those operations occurring last leaving behind true (non-zero).

Scripts are big-endian.

The stacks hold byte vectors. Byte vectors are interpreted as little-endian variable-length integers with the most significant bit determining the sign of the integer. Thus 0x81 represents -1. 0x80 is another representation of zero (so called negative 0). Byte vectors are interpreted as Booleans where False is represented by any representation of zero, and True is represented by any representation of non-zero.

Words

This is a list of all Script words (commands/functions). Some of the more complicated opcodes are disabled out of concern that the client might have a bug in their implementation; if a transaction using such an opcode were to be included in the chain any fix would risk forking the chain.

True=1 and False=0.

Constants

When talking about scripts, these value-pushing words are usually omitted.

Word Opcode Hex Input Output Description
OP_0, OP_FALSE 0 0x00 Nothing. (empty value) An empty array of bytes is pushed onto the stack. (This is not a no-op: an item is added to the stack.)
N/A 1-75 0x01-0x4b (special) data The next opcode bytes is data to be pushed onto the stack
OP_PUSHDATA1 76 0x4c (special) data The next byte contains the number of bytes to be pushed onto the stack.
OP_PUSHDATA2 77 0x4d (special) data The next two bytes contain the number of bytes to be pushed onto the stack.
OP_PUSHDATA4 78 0x4e (special) data The next four bytes contain the number of bytes to be pushed onto the stack.
OP_1NEGATE 79 0x4f Nothing. -1 The number -1 is pushed onto the stack.
OP_1, OP_TRUE 81 0x51 Nothing. 1 The number 1 is pushed onto the stack.
OP_2-OP_16 82-96 0x52-0x60 Nothing. 2-16 The number in the word name (2-16) is pushed onto the stack.

Flow control

Word Opcode Hex Input Output Description
OP_NOP 97 0x61 Nothing Nothing Does nothing.
OP_IF 99 0x63 <expression> if [statements] [else [statements]]* endif If the top stack value is not 0, the statements are executed. The top stack value is removed.
OP_NOTIF 100 0x64 <expression> if [statements] [else [statements]]* endif If the top stack value is 0, the statements are executed. The top stack value is removed.
OP_ELSE 103 0x67 <expression> if [statements] [else [statements]]* endif If the preceding OP_IF or OP_NOTIF or OP_ELSE was not executed then these statements are and if the preceding OP_IF or OP_NOTIF or OP_ELSE was executed then these statements are not.
OP_ENDIF 104 0x68 <expression> if [statements] [else [statements]]* endif Ends an if/else block.
OP_VERIFY 105 0x69 True / false Nothing / False Marks transaction as invalid if top stack value is not true. True is removed, but false is not.
OP_RETURN 106 0x6a Nothing Nothing Marks transaction as invalid.

Stack

Word Opcode Hex Input Output Description
OP_TOALTSTACK 107 0x6b x1 (alt)x1 Puts the input onto the top of the alt stack. Removes it from the main stack.
OP_FROMALTSTACK 108 0x6c (alt)x1 x1 Puts the input onto the top of the main stack. Removes it from the alt stack.
OP_IFDUP 115 0x73 x x / x x If the top stack value is not 0, duplicate it.
OP_DEPTH 116 0x74 Nothing <Stack size> Puts the number of stack items onto the stack.
OP_DROP 117 0x75 x Nothing Removes the top stack item.
OP_DUP 118 0x76 x x x Duplicates the top stack item.
OP_NIP 119 0x77 x1 x2 x2 Removes the second-to-top stack item.
OP_OVER 120 0x78 x1 x2 x1 x2 x1 Copies the second-to-top stack item to the top.
OP_PICK 121 0x79 xn ... x2 x1 x0 <n> xn ... x2 x1 x0 xn The item n back in the stack is copied to the top.
OP_ROLL 122 0x7a xn ... x2 x1 x0 <n> ... x2 x1 x0 xn The item n back in the stack is moved to the top.
OP_ROT 123 0x7b x1 x2 x3 x2 x3 x1 The top three items on the stack are rotated to the left.
OP_SWAP 124 0x7c x1 x2 x2 x1 The top two items on the stack are swapped.
OP_TUCK 125 0x7d x1 x2 x2 x1 x2 The item at the top of the stack is copied and inserted before the second-to-top item.
OP_2DROP 109 0x6d x1 x2 Nothing Removes the top two stack items.
OP_2DUP 110 0x6e x1 x2 x1 x2 x1 x2 Duplicates the top two stack items.
OP_3DUP 111 0x6f x1 x2 x3 x1 x2 x3 x1 x2 x3 Duplicates the top three stack items.
OP_2OVER 112 0x70 x1 x2 x3 x4 x1 x2 x3 x4 x1 x2 Copies the pair of items two spaces back in the stack to the front.
OP_2ROT 113 0x71 x1 x2 x3 x4 x5 x6 x3 x4 x5 x6 x1 x2 The fifth and sixth items back are moved to the top of the stack.
OP_2SWAP 114 0x72 x1 x2 x3 x4 x3 x4 x1 x2 Swaps the top two pairs of items.

Splice

Word Opcode Hex Input Output Description
OP_CAT 126 0x7e x1 x2 out Concatenates two strings. Currently disabled.
OP_SUBSTR 127 0x7f in begin size out Returns a section of a string. Currently disabled.
OP_LEFT 128 0x80 in size out Keeps only characters left of the specified point in a string. Currently disabled.
OP_RIGHT 129 0x81 in size out Keeps only characters right of the specified point in a string. Currently disabled.
OP_SIZE 130 0x82 in in size Returns the length of the input string.

Bitwise logic

Word Opcode Hex Input Output Description
OP_INVERT 131 0x83 in out Flips all of the bits in the input. Currently disabled.
OP_AND 132 0x84 x1 x2 out Boolean and between each bit in the inputs. Currently disabled.
OP_OR 133 0x85 x1 x2 out Boolean or between each bit in the inputs. Currently disabled.
OP_XOR 134 0x86 x1 x2 out Boolean exclusive or between each bit in the inputs. Currently disabled.
OP_EQUAL 135 0x87 x1 x2 True / false Returns 1 if the inputs are exactly equal, 0 otherwise.
OP_EQUALVERIFY 136 0x88 x1 x2 True / false Same as OP_EQUAL, but runs OP_VERIFY afterward.

Arithmetic

Arithmetic is limited to max 4 byte integers

Word Opcode Hex Input Output Description
OP_1ADD 139 0x8b in out 1 is added to the input.
OP_1SUB 140 0x8c in out 1 is subtracted from the input.
OP_2MUL 141 0x8d in out The input is multiplied by 2. Currently disabled.
OP_2DIV 142 0x8e in out The input is divided by 2. Currently disabled.
OP_NEGATE 143 0x8f in out The sign of the input is flipped.
OP_ABS 144 0x90 in out The input is made positive.
OP_NOT 145 0x91 in out If the input is 0 or 1, it is flipped. Otherwise the output will be 0.
OP_0NOTEQUAL 146 0x92 in out Returns 0 if the input is 0. 1 otherwise.
OP_ADD 147 0x93 a b out a is added to b.
OP_SUB 148 0x94 a b out b is subtracted from a.
OP_MUL 149 0x95 a b out a is multiplied by b. Currently disabled.
OP_DIV 150 0x96 a b out a is divided by b. Currently disabled.
OP_MOD 151 0x97 a b out Returns the remainder after dividing a by b. Currently disabled.
OP_LSHIFT 152 0x98 a b out Shifts a left b bits, preserving sign. Currently disabled.
OP_RSHIFT 153 0x99 a b out Shifts a right b bits, preserving sign. Currently disabled.
OP_BOOLAND 154 0x9a a b out If both a and b are not 0, the output is 1. Otherwise 0.
OP_BOOLOR 155 0x9b a b out If a or b is not 0, the output is 1. Otherwise 0.
OP_NUMEQUAL 156 0x9c a b out Returns 1 if the numbers are equal, 0 otherwise.
OP_NUMEQUALVERIFY 157 0x9d a b out Same as OP_NUMEQUAL, but runs OP_VERIFY afterward.
OP_NUMNOTEQUAL 158 0x9e a b out Returns 1 if the numbers are not equal, 0 otherwise.
OP_LESSTHAN 159 0x9f a b out Returns 1 if a is less than b, 0 otherwise.
OP_GREATERTHAN 160 0xa0 a b out Returns 1 if a is greater than b, 0 otherwise.
OP_LESSTHANOREQUAL 161 0xa1 a b out Returns 1 if a is less than or equal to b, 0 otherwise.
OP_GREATERTHANOREQUAL 162 0xa2 a b out Returns 1 if a is greater than or equal to b, 0 otherwise.
OP_MIN 163 0xa3 a b out Returns the smaller of a and b.
OP_MAX 164 0xa4 a b out Returns the larger of a and b.
OP_WITHIN 165 0xa5 x min max out Returns 1 if x is within the specified range (left-inclusive), 0 otherwise.

Crypto

Word Opcode Hex Input Output Description
OP_RIPEMD160 166 0xa6 in hash The input is hashed using RIPEMD-160.
OP_SHA1 167 0xa7 in hash The input is hashed using SHA-1.
OP_SHA256 168 0xa8 in hash The input is hashed using SHA-256.
OP_HASH160 169 0xa9 in hash The input is hashed twice: first with SHA-256 and then with RIPEMD-160.
OP_HASH256 170 0xaa in hash The input is hashed two times with SHA-256.
OP_CODESEPARATOR 171 0xab Nothing Nothing All of the signature checking words will only match signatures to the data after the most recently-executed OP_CODESEPARATOR.
OP_CHECKSIG 172 0xac sig pubkey True / false The entire transaction's outputs, inputs, and script (from the most recently-executed OP_CODESEPARATOR to the end) are hashed. The signature used by OP_CHECKSIG must be a valid signature for this hash and public key. If it is, 1 is returned, 0 otherwise.
OP_CHECKSIGVERIFY 173 0xad sig pubkey True / false Same as OP_CHECKSIG, but OP_VERIFY is executed afterward.
OP_CHECKMULTISIG 174 0xae x sig1 sig2 ... <number of signatures> pub1 pub2 <number of public keys> True / False For each signature and public key pair, OP_CHECKSIG is executed. If more public keys than signatures are listed, some key/sig pairs can fail. All signatures need to match a public key. If all signatures are valid, 1 is returned, 0 otherwise. Due to a bug, one extra unused value is removed from the stack.
OP_CHECKMULTISIGVERIFY 175 0xaf x sig1 sig2 ... <number of signatures> pub1 pub2 ... <number of public keys> True / False Same as OP_CHECKMULTISIG, but OP_VERIFY is executed afterward.

Pseudo-words

These words are used internally for assisting with transaction matching. They are invalid if used in actual scripts.

Word Opcode Hex Description
OP_PUBKEYHASH 253 0xfd Represents a public key hashed with OP_HASH160.
OP_PUBKEY 254 0xfe Represents a public key compatible with OP_CHECKSIG.
OP_INVALIDOPCODE 255 0xff Matches any opcode that is not yet assigned.

Reserved words

Any opcode not assigned is also reserved. Using an unassigned opcode makes the transaction invalid.

Word Opcode Hex When used...
OP_RESERVED 80 0x50 Transaction is invalid unless occuring in an unexecuted OP_IF branch
OP_VER 98 0x62 Transaction is invalid unless occuring in an unexecuted OP_IF branch
OP_VERIF 101 0x65 Transaction is invalid even when occuring in an unexecuted OP_IF branch
OP_VERNOTIF 102 0x66 Transaction is invalid even when occuring in an unexecuted OP_IF branch
OP_RESERVED1 137 0x89 Transaction is invalid unless occuring in an unexecuted OP_IF branch
OP_RESERVED2 138 0x8a Transaction is invalid unless occuring in an unexecuted OP_IF branch
OP_NOP1-OP_NOP10 176-185 0xb0-0xb9 The word is ignored.

Scripts

This is a list of interesting scripts. Keep in mind that all constants actually use the data-pushing commands above.

Standard Transaction to Bitcoin address

scriptPubKey: OP_DUP OP_HASH160 <pubKeyHash> OP_EQUALVERIFY OP_CHECKSIG
scriptSig: <sig> <pubKey>

To demonstrate how scripts look on the wire, here is a raw scriptPubKey:

  76       A9             14
OP_DUP OP_HASH160    Bytes to push

89 AB CD EF AB BA AB BA AB BA AB BA AB BA AB BA AB BA AB BA   88         AC
                      Data to push                     OP_EQUALVERIFY OP_CHECKSIG

Note: scriptSig is in the input of the spending transaction and scriptPubKey is in the output of the previously unspent i.e. "available" transaction.

Here is how each word is processed:

Stack Script Description
Empty. <sig> <pubKey> OP_DUP OP_HASH160 <pubKeyHash> OP_EQUALVERIFY OP_CHECKSIG scriptSig and scriptPubKey are combined.
<sig> <pubKey> OP_DUP OP_HASH160 <pubKeyHash> OP_EQUALVERIFY OP_CHECKSIG Constants are added to the stack.
<sig> <pubKey> <pubKey> OP_HASH160 <pubKeyHash> OP_EQUALVERIFY OP_CHECKSIG Top stack item is duplicated.
<sig> <pubKey> <pubHashA> <pubKeyHash> OP_EQUALVERIFY OP_CHECKSIG Top stack item is hashed.
<sig> <pubKey> <pubHashA> <pubKeyHash> OP_EQUALVERIFY OP_CHECKSIG Constant added.
<sig> <pubKey> OP_CHECKSIG Equality is checked between the top two stack items.
true Empty. Signature is checked for top two stack items.

Standard Generation / transaction to IP address

scriptPubKey: <pubKey> OP_CHECKSIG
scriptSig: <sig>

Checking process:

Stack Script Description
Empty. <sig> <pubKey> OP_CHECKSIG scriptSig and scriptPubKey are combined.
<sig> <pubKey> OP_CHECKSIG Constants are added to the stack.
true Empty. Signature is checked for top two stack items.

Transaction with a message

It's possible to add arbitrary data to any transaction by just adding some data along with OP_DROP. Scripts are limited to 10,000 bytes and 201 instructions, and each individual instruction/value is limited to 520 bytes.

scriptPubKey: <message> OP_DROP <pubKey> OP_CHECKSIG
scriptSig: <sig>
Stack Script Description
Empty. <sig> <message> OP_DROP <pubKey> OP_CHECKSIG
<sig> <message> OP_DROP <pubKey> OP_CHECKSIG scriptSig added to the stack.
<sig> <message> OP_DROP <pubKey> OP_CHECKSIG The message has been put.
<sig> <pubKey> OP_CHECKSIG Top stack item has been removed.
<sig> <pubKey> OP_CHECKSIG Checking signature against the public key.
true Empty. Stack holds the value of signature check now.

Example non standard transaction on Testnet

These 2 links below show a non standard transaction. It just prepends the hex of "bob" and the operation OP_DROP which just removes it. As you can see they can be spent as normal.

Input non-std transaction: http://blockexplorer.com/testnet/t/6ttfeb55B1

Spent by: http://blockexplorer.com/testnet/t/AFdRB1CHS3

See Also