developed with
btcpy
btcpy is a Python>=3.3 SegWit-compliant library which provides tools to handleBitcoin data structures in a simple fashion. In particular, the main goal ofthis library is to provide a simple interface to parse and create complexBitcoin scripts.
N.B.: this library is a work in progress so it is highly discouraged to use it ina production environment. Also, as long as the version is 0.*, API breaking changesshould be expected
Table of Contents
- btcpy
- Table of Contents
- Requirements
- Installation
- What it does
- What it does not do
- Structure
- Usage examples
- Contributing and running tests
- Roadmap to v1
- TODO
- Acknowledgements
Requirements
The strict requirements of this library are:
pip install ecdsa
pip install base58
as an additional requirement, only used for integration testing purposes, thislibrary uses:
pip install python-bitcoinlib==0.7.0
this is used to communicate with the Bitcoin node in order to test transactionsvalidation.
Installation
To install this library and its dependencies one can just run
pip install chainside-btcpy
What it does
The main functionalities provided by this project are the following.
Parsing of blocks
Parsing, creation and signing of transactions
Parsing and creation of scripts. This also includes many nonstandard scripttypes such as:
- Hashlocked scripts
- Timelocked scripts, with both absolute and relative times
- Arbitrarily nested if-else clauses
all scripts are easily embeddable in P2SH and P2WSH format, alsosupporting SegWit-over-P2SH formats. This library also offers functions tospend such complex scripts by only providing the necessary data.
What it does not do
This library does not implement the following functionalities:
- Validation: when blocks, transactions and scripts are parsed, onlyformat errors are reported. No proof-of-work validation, script execution,transaction validation and signature verification is performed. For theseconsensus-critical functionalities, users of this library should rely onBitcoin Core or other libraries that perform validation.
- Communication with the Bitcoin nodes. This is not provided neither on an RPCnor a networking level. For this purpose we highly recommed python-bitcoinlib.
Structure
All important data structures can be found in btcpy.structs, helper modulesare located in btcpy.lib. Objects in btcpy.structs are meant as a publicinterface, while objects located in btcpy.lib are used internally.
Usage examples
Setup
The first thing to do the first time this package is imported is to set a global state whichindicates on which network you are working and wether you want strict mode enabled.These two settings are further explained in the following sections.
To setup btcpy, you can use the following function
from btcpy.setup import setup
setup('regtest', strict=True)
Network
You can setup the network you will work on by calling:
from btcpy.setup import setup
setup('regtest')
supported network types are:
regtest
testnet
mainnet
The btcpy.setup module also provides the following network-related functions:
is_mainnet() - returns True if 'mainnet' was selected, False otherwise
net_name() - returns the value that was selected when calling setup()
Strictness
btcpy never performs validation. However, we don't want you to inadvertently lose your fundsfor a mistake, so, in strict mode, when you do something that looks dangerous, the libraryalways makes sure that you know exactly what you are doing.
To setup the library in strict mode, you can run the setup as follows:
setup(my_network, strict=True) # True is actually the default for strict mode, the only other option is False
Additionally, you can force (non-)strictness on specific functions that have a strict=Noneas keyword argument. If the strict keyword argument is left to None, then the strictnessspecified in the setup will be followed, otherwise the param you pass to strict will be used.
The following additional checks are done when in strict mode:
- Do not allow to create
P2pkScripts with public keys that have an invalid format (please note thatduring parsing such scripts will not even be recognised as scripts of type'p2pk'when strict mode is enabled, they will instead be recognised as of type'nonstandard') - Do not allow to create m-of-n
MultisigScripts with less thanmpublic keys that have a valid format(please note that during parsing such scripts will not even be recognised as scripts of type'multisig'when strict mode is enabled, they will instead be recognised as of type'nonstandard') - Do not allow to decode
ExtendedPublicKeysorExtendedPrivateKeysthat don't match the network you set insetup - Do not allow to decode
Addresses that don't match the network you set insetup
Parsing and serialization
Transaction, PublicKey, PrivateKey and Block can be extractedfrom a hex string by doing:
from btcpy.structs.transaction import Transaction
from btcpy.structs.block import Block
from btcpy.structs.crypto import PublicKey, PrivateKey
tx = Transaction.unhexlify(hex_tx)
block = Block.unhexlify(hex_block)
pubk = PublicKey.unhexlify(pubk_hex)
privk = PrivateKey.unhexlify(privk_hex)
PublicKey and PrivateKey can also be extracted from their BIP32 formats using thehd module:
>>> from btcpy.structs.hd import ExtendedPrivateKey, ExtendedPublicKey
>>> priv = ExtendedPrivateKey.decode('tprv8kxXxKwakWDtXvKBjjR5oHDFS7Z21HCVLMVUqEFCSVChUZ26BMDDH1JmaGUTEYGMUyQQBSfTgEK76QBvLephodJid5GTEiGFVGJdEBYptd7')
# priv.key holds a `PrivateKey`
>>> priv.key.hexlify()
'a12618ff6540dcd79bf68fda2faf0589b672e18b99a1ebcc32a40a67acdab608'
>>> pub = ExtendedPublicKey.decode('tpubDHea6jyptsuZRPLydP5gCgsN194xAcPPuf6G7kHVrm16K3Grok2oTVvdkNvPM465uuKAShgba7A2hHYeGGuS9B8AQGABfc6hp7mpcLLJUsk')
# pub.key holds a `PublicKey`
>>> pub.key.hexlify()
'025f628d7a11ace2a6379119a778240cb70d6e720750416bb36f824514fbe88260'
PrivateKey can also be extracted from a Wallet Import Format by doing:
>>> privk = PrivateKey.form_wif(wif_key)
All these structures can be converted back to hex by using their hexlify() method.
In the same way, these structures can be serialized and deserialized by using theirserialize() and deserialize() methods. These methods respectively return andexpect a bytearray type.
Keys
The PublicKey class can handle both compressed and uncompressed publickeys. In any case both the compressed and uncompressed version can be extracted.However, the structure will remember how it was initialised, so the hexlify(),hash() and to_address() methods will produce differentresults depending whether the PublicKey was initialised with a compressed oruncompressed public key. The to_segwit_address() method will always considerthe key as compressed (P2WPKH addresses are only allowed with compressed keys).An example of this behaviour follows:
>>> uncomp = PublicKey.unhexlify('04ea4e183e8c751a4cc72abb7088cea79351dbfb7981ceb48f286ccfdade4d42c877d334c1a8b34072400f71b2a900a305ffae8963075fe94ea439b4b57978e9e8')
>>> compr = PublicKey(uncomp.compressed)
>>> uncomp.hexlify()
'04ea4e183e8c751a4cc72abb7088cea79351dbfb7981ceb48f286ccfdade4d42c877d334c1a8b34072400f71b2a900a305ffae8963075fe94ea439b4b57978e9e8'
>>> compr.hexlify()
'02ea4e183e8c751a4cc72abb7088cea79351dbfb7981ceb48f286ccfdade4d42c8'
>>> str(uncomp.to_address())
'mtDD9VFhPaRi6C6McMSnhb7nUZceSh4MnK'
>>> str(uncomp.to_segwit_address())
'tb1qxs0gs9dzukv863jud3wpldtrjh9edeqqqzahcz' # this actually refers to the compressed version!
>>> str(compr.to_address())
'mkGY1QBotzNCrpJaEsje3BpYJsktksi3gJ'
>>> str(compr.to_segwit_address())
'tb1qxs0gs9dzukv863jud3wpldtrjh9edeqqqzahcz'
Please note that by default the to_address() and to_segwit_address()methods will return an address in the format of the network typespecified in setup (regtest in the case of this example) but a flagcan be passed to it to return an address for another network:
>>> str(uncomp.to_address(mainnet=True))
'1DhFrSAiaYzTK5cjtnUQsfuTca1wXvXfVY'
>>> str(compr.to_address(mainnet=True))
'15kaiM6q5xvx5hpxXJmGDGcDStABoGTzSX'
The PublicKey derived from a PrivateKey can be obtained by doing:
pubk = PrivateKey.unhexlify(privk_hex).pub()
the pub() method will return by default the compressed public key.The uncompressed version can be obtained by adding the flag compressed=False.
Additionally, one can make sure to use the compressed version of a key byusing its compress() method:
>>> compr = uncomp.compress()
>>> str(compr.to_address())
'mkGY1QBotzNCrpJaEsje3BpYJsktksi3gJ'
Addresses can be either created from a PublicKey or from a script.In particular this second use case will be documented in the Addresses section.
HD keys
The structs.hd module provides functionalities to handle BIP32 HD keys.Specifically, it provides the following two classes:
ExtendedPublicKeyExtendedPrivateKey
These classes both provide the get_child(index, hardened=False) method. Ifcalled on an ExtendedPublicKey, hardened must be set to False, otherwiseheardened can be either True or False. The ExtendedPublicKey correspondingto an ExtendedPrivateKey can be obtained through the pub() method.
As seen in the example above, ExtendedPublicKey and ExtendedPrivateKeycontain the simpler structures PublicKey and PrivateKey, respectively.These structures can be accessed through the key attribute.
ExtendedPublicKeys also provide a derive() method which takes as input a stringrepresenting a path which either starts with 'm' or with '.'. 'm' indicates anabsolute path and can be used only when derive() is called on a master key, '.'represents a relative path and can be used from any starting key. Examples ofderivation paths:
m/0'/1'/2: absolute path, first two derivations hardened./0/128/256': relative path, last derivation hardened
Scripts
The main focus of this project is providing a simple way to create complex scripts. Scripts havethe following hierarchy
BaseScriptScriptSigScriptPubKeyP2pkhscriptP2wpkhScriptP2wpkhV0Script
P2shScriptP2wshScriptP2wshV0Script
P2pkScriptNulldataScriptMultisigScriptIfElseScriptAbsoluteTimelockScriptRelativeTimelockScriptHashlock256ScriptHashlock160ScriptUnknownScript
Scripts have the following methods:
serialize() - Returns the script as a bytearray
decompile() - Returns a string representing the human readable opcodes and pushdata operations
hexlify() - Returns the script as a hex string
unhexlify(hex_string) - Creates the script from a hex string
is_standard() - Returns whether the script complies with standardness rules as of Bitcoin Core commit a90e6d2bffc422ddcdb771c53aac0bceb970a2c4
type - A property containing a string which represents the type of the script
get_sigop_count() - Returns the number of signature operations performed by the script
is_push_only() - Returns whether the script is only made of push operations
to_address(segwit=False) - (only ScriptPubKey) Returns the script as either a P2SH or a P2WSH address, depending whether
the segwit flag is set
Low-level scripting functionalities
This section will introduce low-level creation and template-matching of scripts,for more advanced features please refer to the Transactions section.
This libary allows to create scripts from asm and from hex, as can be seen inthe following examples.
Creating a script from asm (i.e. opcodes):
# this returns a bytearray with the compiled script
>>> compiled = Script.compile('OP_DUP OP_HASH160 a33ce8cf2760e2f9ef384bcbbe9a5491759feb14 OP_EQUALVERIFY OP_CHECKSIG')
# the bytearray can be passed to Script() to get a generic script
>>> script = Script(compiled)
# check that everything works as expected
>>> script.decompile()
'OP_DUP OP_HASH160 a33ce8cf2760e2f9ef384bcbbe9a5491759feb14 OP_EQUALVERIFY OP_CHECKSIG'
# beware, this is a generic script, no type recognition has been performed!
>>> script.type
'Script'
Creating a script from hex:
# this returns a bytearray with the compiled script
>>> script = Script.unhexlify('76a914a33ce8cf2760e2f9ef384bcbbe9a5491759feb1488ac')
# check that everything works as expected
>>> script.decompile()
'OP_DUP OP_HASH160 a33ce8cf2760e2f9ef384bcbbe9a5491759feb14 OP_EQUALVERIFY OP_CHECKSIG'
# beware, this is a generic script, no type recognition has been performed!
>>> script.type
'Script'
As we have seen, these are instantiated as generic scripts, if we want to obtain the appropriatescript type, the ScriptBuilder class can be used. ScriptBuilder's method identify()will return the appropriate script type by performing template matching on the providedscript.
Identifying a P2PKH script:
>>> script = ScriptBuilder.identify('76a914341e8815a2e5987d465c6c5c1fb56395cb96e40088ac')
>>> script.type
'p2pkh'
>>> script.decompile()
'OP_DUP OP_HASH160 341e8815a2e5987d465c6c5c1fb56395cb96e400 OP_EQUALVERIFY OP_CHECKSIG'
>>> script.pubkeyhash
bytearray(b'4\x1e\x88\x15\xa2\xe5\x98}F\\l\\\x1f\xb5c\x95\xcb\x96\xe4\x00')
Identifying a P2SH script
>>> script = ScriptBuilder.identify('a914bb18ed39c2a86f75f7bb5a9b36ba3581d77fd0f087')
>>> script.type
'p2sh'
>>> script.decompile()
'OP_HASH160 bb18ed39c2a86f75f7bb5a9b36ba3581d77fd0f0 OP_EQUAL'
>>> script.scripthash
bytearray(b'\xbb\x18\xed9\xc2\xa8ou\xf7\xbbZ\x9b6\xba5\x81\xd7\x7f\xd0\xf0')
Of course, all the types listed at the beginning of this section can be recognised,see the next section for more complex script types.
Please keep in mind that the fact that a script is successfully built (a script can be builtfor every recognised script type, if no type matches, an UnknownScript is istantiated) doesnot mean that the script is valid. In fact, UnknownScripts can even contain non valid pushoperations or non-existing opcodes. The only way to know if a script is valid is executing itagainst an execution stack, a functionality that this library does not implement. In particular,for non-valid push operations, the script asm (obtained through the decompile or __str__ methods)will contain [error] where the push takes place. For non-existing opcodes the asm will containthe special opcode OP_INVALIDOPCODE. These two beahviours match Bitcoin Core's behaviour whenproducing script asm.
Addresses
Supported addresses are: P2pkhAddress, P2shAddress, P2wpkhAddress and P2wshAddress.These constructors can be used to build an address from a hash (plus a SegWit version in thecase of P2wpkhAddress or P2wshAddress), for example:
from btcpy.structs.crypto import PublicKey
from btcpy.structs.address import P2pkhAddress, P2wpkhAddress
pubk = PublicKey.unhexlify('02ea4e183e8c751a4cc72abb7088cea79351dbfb7981ceb48f286ccfdade4d42c8')
address = P2pkhAddress(pubk.hash())
sw_address = P2wpkhAddress(pubk.hash(), version=0)
print(str(address)) # prints "mkGY1QBotzNCrpJaEsje3BpYJsktksi3gJ"
print(str(sw_address)) # prints "tb1qxs0gs9dzukv863jud3wpldtrjh9edeqqqzahcz"
Please note that by default all the address constructors will return an address in theformat of the network type specified in setup (testnet in the case of this example) buta flag can be passed to them to return an address for another network:
address = P2pkhAddress(pubk.hash(), mainnet=True)
sw_address = P2wpkhAddress(pubk.hash(), version=0, mainnet=True)
print(str(address)) # prints "15kaiM6q5xvx5hpxXJmGDGcDStABoGTzSX"
print(str(sw_address)) # prints "bc1qxs0gs9dzukv863jud3wpldtrjh9edeqq2yxyr3"
However, a more common usecase is generating an address for a script, for this the from_scriptstatic method of all address classes can be used, in particular:
P2pkhAddress.from_script(script, mainnet=None)will instantiate aP2pkhAddressfrom aP2pkhScript, raisingWrongScriptTypeexception in case another type of script is provided.P2shAddress.from_script(script, mainnet=None)will instantiate aP2shAddressrepresentingthe script address if aP2shscriptis provided, while returning the address of the scriptembedded in P2SH format if other script types are provided.P2wpkhAddress.from_script(script, version, mainnet=None)will instantiate aP2wpkhAddressfrom aP2wpkhScript, raisingWrongScriptTypeexception in case another type of scriptis provided.P2wshAddress.from_script(script, version, mainnet=None)will instantiate aP2wshAddressrepresenting the script address if aP2wshscriptis provided, while returning the addressof the script embedded in P2WSH format if other script types are provided.
The only scripts that directly support an address (i.e. P2pkhScript, P2wpkhScript,P2shscript, P2wshScript) also provide a helper method address() to return the scriptaddress, for all other script types will return None if the address() method is calledand will need to be explicitly converted to P2SH or P2WSH format to obtain an address. Someexamples follow:
>>> str(P2pkhAddress.from_script(P2pkhScript(pubk)))
'mkGY1QBotzNCrpJaEsje3BpYJsktksi3gJ'
>>> str(P2pkhScript(pubk).address())
'mkGY1QBotzNCrpJaEsje3BpYJsktksi3gJ'
>>> str(P2pkhAddress.from_script(P2shScript(P2pkhScript(pubk))))
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File ".../btcpy/btcpy/structs/address.py", line 120, in from_script
raise WrongScriptType('Trying to produce P2pkhAddress from {} script'.format(script.__class__.__name__))
btcpy.structs.address.WrongScriptType: Trying to produce P2pkhAddress from P2shScript script
>>> str(P2shAddress.from_script(P2shScript(P2pkhScript(pubk))))
'2NAJWD6EnXMVt16HUp5vmfwPjz4FemvPhYt'
>>> str(P2shScript(P2pkhScript(pubk)).address())
'2NAJWD6EnXMVt16HUp5vmfwPjz4FemvPhYt'
>>> str(P2wpkhAddress.from_script(P2wpkhV0Script(pubk)))
'tb1qxs0gs9dzukv863jud3wpldtrjh9edeqqqzahcz'
>>> str(P2wpkhV0Script(pubk).address())
'tb1qxs0gs9dzukv863jud3wpldtrjh9edeqqqzahcz'
>>> str(P2wpkhAddress.from_script(P2shScript(P2wpkhV0Script(pubk))))
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File ".../btcpy/btcpy/structs/address.py", line 158, in from_script
raise WrongScriptType('Trying to produce P2pkhAddress from {} script'.format(script.__class__.__name__))
btcpy.structs.address.WrongScriptType: Trying to produce P2pkhAddress from P2shScript script
On the other hand, addresses can also be directly converted to the scripts they represent:
>>> a = Address.from_string('mkGY1QBotzNCrpJaEsje3BpYJsktksi3gJ')
>>> a.to_script()
P2pkhScript('341e8815a2e5987d465c6c5c1fb56395cb96e400')
>>> a = Address.from_string('tb1qxs0gs9dzukv863jud3wpldtrjh9edeqqqzahcz')
>>> a.to_script()
P2wpkhScript('341e8815a2e5987d465c6c5c1fb56395cb96e400')
Transactions
Creating transactions
Transactions can be created by using the following classes:
TxIn, takes as input the following parameters:txid, the txid of the transaction being spenttxout, the output number of the output being spentscript_sig, a scriptSigsequence, the sequence number of the TxIn
Sequence, the constructor takes a sequence number, but it offers a couple of helper staticmethods for creation:create(), which takesseq, lower 16 bits of sequence number,blocks, whether theseqparam expresses blocks or a timestamp, anddisablewhich sets the disable bit. For furtherinfo on how this all works, please refer toBIP68 specification.max(), this automatically creates aSequenceobject with the maximum sequence number(i.e.0xffffffff).
TimebasedSequence, behaves like aSequencebut assumes the sequence expresses time. Canalso be instantiated from atimedeltaobject through itsfrom_timedeltamethodHeightBasedSequence, behaves like aSequencebut assumes the sequence expresses a block height.ScriptSig, this can be initialised with abytearrayrepresenting the script, but offersthe following static methods:empty(), this creates an emptyScriptSig, useful when initialising a transactionwhich has not been signed yet
StackData, this class represents data that scripts push on the stack, it offers methodsto convert between the push operations and the actual data pushed.Witness, this represents a SegWit witness, it is constructed with an array ofStackData.TxOut, takes as input the following parameters:valuethe value spent, in satoshis,n,the output number,script_pubkey, an object of typeScriptPubKeywhere the coins are beingsent.ScriptPubKeyand derived classes, they take as input abytearrayrepresenting the scriptbut can also be created through theScriptBuilder.identify()method or in the way displayedlater in this section.Locktime, takes as input a number representing the transaction's locktime field. Can alsobe constructed from adatetimeobject through itsfrom_datetimemethodTransaction, takes as inputs: a version number, a list ofTxIns, a list ofTxOuts, aLocktime.SegWitTransaction, has the same interface asTransactionTransactionFactoryused to instantiate a generic transaction from a json or hex string
All the aforementioned classes are Immutable, this means that, after construction, theirattributes can't be mutated. This helps caching values returned by their methods. The classesTransaction, SegWitTransaction and TxIn have mutable versions, unsurprisingly calledMutableTransaction, MutableSegWitTransaction and MutbleTxIn, respectively. These mutableversions are mainly used to create unsigned transactions which then are mutatedto add signatures to them. We will see how to use these in the rest of this section.
Transactions can be deserialized both from json and from a hex string, see the following examples:
>>> tx = Transaction.unhexlify('0100000001e4da173fbefe5e60ff63dfd38566ade407532294db655463b77a783f379ce605000000006b483045022100af246c27890c2bc07a0b7450d3d82509702a44a4defdff766355240b114ee2ac02207bb67b468452fa1b325dd5583879f5c1412e0bb4dae1c2c96c7a408796ab76f1012102ab9e8575536a1e99604a158fc60fe2ebd1cb1839e919b4ca42b8d050cfad71b2ffffffff0100c2eb0b000000001976a914df76c017354ac39bde796abe4294d31de8b5788a88ac00000000')
>>> tx.to_json()
{'hex': '0100000001e4da173fbefe5e60ff63dfd38566ade407532294db655463b77a783f379ce605000000006b483045022100af246c27890c2bc07a0b7450d3d82509702a44a4defdff766355240b114ee2ac02207bb67b468452fa1b325dd5583879f5c1412e0bb4dae1c2c96c7a408796ab76f1012102ab9e8575536a1e99604a158fc60fe2ebd1cb1839e919b4ca42b8d050cfad71b2ffffffff0100c2eb0b000000001976a914df76c017354ac39bde796abe4294d31de8b5788a88ac00000000', 'txid': 'e977c07090c2a1dcaefd3f3c4ebf4e231f4116cb272f805b0b22a85e7eece09c', 'hash': 'e977c07090c2a1dcaefd3f3c4ebf4e231f4116cb272f805b0b22a85e7eece09c', 'size': 192, 'vsize': 192, 'version': 1, 'locktime': 0, 'vin': [{'txid': '05e69c373f787ab7635465db94225307e4ad6685d3df63ff605efebe3f17dae4', 'vout': 0, 'scriptSig': {'asm': '3045022100af246c27890c2bc07a0b7450d3d82509702a44a4defdff766355240b114ee2ac02207bb67b468452fa1b325dd5583879f5c1412e0bb4dae1c2c96c7a408796ab76f101 02ab9e8575536a1e99604a158fc60fe2ebd1cb1839e919b4ca42b8d050cfad71b2', 'hex': '483045022100af246c27890c2bc07a0b7450d3d82509702a44a4defdff766355240b114ee2ac02207bb67b468452fa1b325dd5583879f5c1412e0bb4dae1c2c96c7a408796ab76f1012102ab9e8575536a1e99604a158fc60fe2ebd1cb1839e919b4ca42b8d050cfad71b2'}, 'sequence': '4294967295'}], 'vout': [{'value': '2.00000000', 'n': 0, 'scriptPubKey': {'asm': 'OP_DUP OP_HASH160 df76c017354ac39bde796abe4294d31de8b5788a OP_EQUALVERIFY OP_CHECKSIG', 'hex': '76a914df76c017354ac39bde796abe4294d31de8b5788a88ac', 'type': 'p2pkh', 'address': '1MNZwhTBHN3QTXkwob7NvhVaTVKUm7MRCg'}}]}
>>> tx = SegWitTransaction.unhexlify('0100000001e4da173fbefe5e60ff63dfd38566ade407532294db655463b77a783f379ce605000000006b483045022100af246c27890c2bc07a0b7450d3d82509702a44a4defdff766355240b114ee2ac02207bb67b468452fa1b325dd5583879f5c1412e0bb4dae1c2c96c7a408796ab76f1012102ab9e8575536a1e99604a158fc60fe2ebd1cb1839e919b4ca42b8d050cfad71b2ffffffff0100c2eb0b000000001976a914df76c017354ac39bde796abe4294d31de8b5788a88ac00000000')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/rael/Dropbox/projects/btcpy/btcpy/structs/transaction.py", line 457, in unhexlify
return cls.deserialize(bytearray(unhexlify(string)))
File "/home/rael/Dropbox/projects/btcpy/btcpy/structs/transaction.py", line 466, in deserialize
raise TypeError('Trying to load transaction from wrong transaction serialization')
TypeError: Trying to load transaction from wrong transaction serialization
>>> tx = Transaction.from_json({'hex': '0100000001e4da173fbefe5e60ff63dfd38566ade407532294db655463b77a783f379ce605000000006b483045022100af246c27890c2bc07a0b7450d3d82509702a44a4defdff766355240b114ee2ac02207bb67b468452fa1b325dd5583879f5c1412e0bb4dae1c2c96c7a408796ab76f1012102ab9e8575536a1e99604a158fc60fe2ebd1cb1839e919b4ca42b8d050cfad71b2ffffffff0100c2eb0b000000001976a914df76c017354ac39bde796abe4294d31de8b5788a88ac00000000', 'txid': 'e977c07090c2a1dcaefd3f3c4ebf4e231f4116cb272f805b0b22a85e7eece09c', 'hash': 'e977c07090c2a1dcaefd3f3c4ebf4e231f4116cb272f805b0b22a85e7eece09c', 'size': 192, 'vsize': 192, 'version': 1, 'locktime': 0, 'vin': [{'txid': '05e69c373f787ab7635465db94225307e4ad6685d3df63ff605efebe3f17dae4', 'vout': 0, 'scriptSig': {'asm': '3045022100af246c27890c2bc07a0b7450d3d82509702a44a4defdff766355240b114ee2ac02207bb67b468452fa1b325dd5583879f5c1412e0bb4dae1c2c96c7a408796ab76f101 02ab9e8575536a1e99604a158fc60fe2ebd1cb1839e919b4ca42b8d050cfad71b2', 'hex': '483045022100af246c27890c2bc07a0b7450d3d82509702a44a4defdff766355240b114ee2ac02207bb67b468452fa1b325dd5583879f5c1412e0bb4dae1c2c96c7a408796ab76f1012102ab9e8575536a1e99604a158fc60fe2ebd1cb1839e919b4ca42b8d050cfad71b2'}, 'sequence': '4294967295'}], 'vout': [{'value': '2.00000000', 'n': 0, 'scriptPubKey': {'asm': 'OP_DUP OP_HASH160 df76c017354ac39bde796abe4294d31de8b5788a OP_EQUALVERIFY OP_CHECKSIG', 'hex': '76a914df76c017354ac39bde796abe4294d31de8b5788a88ac', 'type': 'p2pkh', 'address': '1MNZwhTBHN3QTXkwob7NvhVaTVKUm7MRCg'}}]})
>>> tx = SegWitTransaction.from_json({'hex': '0100000001e4da173fbefe5e60ff63dfd38566ade407532294db655463b77a783f379ce605000000006b483045022100af246c27890c2bc07a0b7450d3d82509702a44a4defdff766355240b114ee2ac02207bb67b468452fa1b325dd5583879f5c1412e0bb4dae1c2c96c7a408796ab76f1012102ab9e8575536a1e99604a158fc60fe2ebd1cb1839e919b4ca42b8d050cfad71b2ffffffff0100c2eb0b000000001976a914df76c017354ac39bde796abe4294d31de8b5788a88ac00000000', 'txid': 'e977c07090c2a1dcaefd3f3c4ebf4e231f4116cb272f805b0b22a85e7eece09c', 'hash': 'e977c07090c2a1dcaefd3f3c4ebf4e231f4116cb272f805b0b22a85e7eece09c', 'size': 192, 'vsize': 192, 'version': 1, 'locktime': 0, 'vin': [{'txid': '05e69c373f787ab7635465db94225307e4ad6685d3df63ff605efebe3f17dae4', 'vout': 0, 'scriptSig': {'asm': '3045022100af246c27890c2bc07a0b7450d3d82509702a44a4defdff766355240b114ee2ac02207bb67b468452fa1b325dd5583879f5c1412e0bb4dae1c2c96c7a408796ab76f101 02ab9e8575536a1e99604a158fc60fe2ebd1cb1839e919b4ca42b8d050cfad71b2', 'hex': '483045022100af246c27890c2bc07a0b7450d3d82509702a44a4defdff766355240b114ee2ac02207bb67b468452fa1b325dd5583879f5c1412e0bb4dae1c2c96c7a408796ab76f1012102ab9e8575536a1e99604a158fc60fe2ebd1cb1839e919b4ca42b8d050cfad71b2'}, 'sequence': '4294967295'}], 'vout': [{'value': '2.00000000', 'n': 0, 'scriptPubKey': {'asm': 'OP_DUP OP_HASH160 df76c017354ac39bde796abe4294d31de8b5788a OP_EQUALVERIFY OP_CHECKSIG', 'hex': '76a914df76c017354ac39bde796abe4294d31de8b5788a88ac', 'type': 'p2pkh', 'address': '1MNZwhTBHN3QTXkwob7NvhVaTVKUm7MRCg'}}]})
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/rael/Dropbox/projects/btcpy/btcpy/structs/transaction.py", line 737, in from_json
raise TypeError('Trying to load segwit transaction from non-segwit transaction json')
TypeError: Trying to load segwit transaction from non-segwit transaction json
As you can see from the previous example, Transaction and SegWitTransaction classes can deserialise onlyjson and hex strings of the appropriate type. To deserialize a generic json or hex string and build theappropriate object, one can use the TransactionFactory:
>>> TransactionFactory.unhexlify('0100000001e4da173fbefe5e60ff63dfd38566ade407532294db655463b77a783f379ce605000000006b483045022100af246c27890c2bc07a0b7450d3d82509702a44a4defdff766355240b114ee2ac02207bb67b468452fa1b325dd5583879f5c1412e0bb4dae1c2c96c7a408796ab76f1012102ab9e8575536a1e99604a158fc60fe2ebd1cb1839e919b4ca42b8d050cfad71b2ffffffff0100c2eb0b000000001976a914df76c017354ac39bde796abe4294d31de8b5788a88ac00000000')
<btcpy.structs.transaction.Transaction object at 0x7f3717961be0>
>>> TransactionFactory.from_json({'hex': '0100000001e4da173fbefe5e60ff63dfd38566ade407532294db655463b77a783f379ce605000000006b483045022100af246c27890c2bc07a0b7450d3d82509702a44a4defdff766355240b114ee2ac02207bb67b468452fa1b325dd5583879f5c1412e0bb4dae1c2c96c7a408796ab76f1012102ab9e8575536a1e99604a158fc60fe2ebd1cb1839e919b4ca42b8d050cfad71b2ffffffff0100c2eb0b000000001976a914df76c017354ac39bde796abe4294d31de8b5788a88ac00000000', 'txid': 'e977c07090c2a1dcaefd3f3c4ebf4e231f4116cb272f805b0b22a85e7eece09c', 'hash': 'e977c07090c2a1dcaefd3f3c4ebf4e231f4116cb272f805b0b22a85e7eece09c', 'size': 192, 'vsize': 192, 'version': 1, 'locktime': 0, 'vin': [{'txid': '05e69c373f787ab7635465db94225307e4ad6685d3df63ff605efebe3f17dae4', 'vout': 0, 'scriptSig': {'asm': '3045022100af246c27890c2bc07a0b7450d3d82509702a44a4defdff766355240b114ee2ac02207bb67b468452fa1b325dd5583879f5c1412e0bb4dae1c2c96c7a408796ab76f101 02ab9e8575536a1e99604a158fc60fe2ebd1cb1839e919b4ca42b8d050cfad71b2', 'hex': '483045022100af246c27890c2bc07a0b7450d3d82509702a44a4defdff766355240b114ee2ac02207bb67b468452fa1b325dd5583879f5c1412e0bb4dae1c2c96c7a408796ab76f1012102ab9e8575536a1e99604a158fc60fe2ebd1cb1839e919b4ca42b8d050cfad71b2'}, 'sequence': '4294967295'}], 'vout': [{'value': '2.00000000', 'n': 0, 'scriptPubKey': {'asm': 'OP_DUP OP_HASH160 df76c017354ac39bde796abe4294d31de8b5788a OP_EQUALVERIFY OP_CHECKSIG', 'hex': '76a914df76c017354ac39bde796abe4294d31de8b5788a88ac', 'type': 'p2pkh', 'address': '1MNZwhTBHN3QTXkwob7NvhVaTVKUm7MRCg'}}]})
<btcpy.structs.transaction.Transaction object at 0x7f3717971518>
Example of a transaction creation:
>>> from btcpy.structs.transaction import Transaction, TxIn, Sequence, TxOut, Locktime
>>> script_sig = Script.unhexlify('48304502210083e6e7507e838a190f0443441c0b62d2df94673887f4482e27e89ff415a90392022050575339c649b85c04bb410a00b62325c1b82c537135fa62fb34fae2c9a30b0b01210384478d41e71dc6c3f9edde0f928a47d1b724c05984ebfb4e7d0422e80abe95ff')
>>> script_pubkey = ScriptBuilder.identify('76a914905f77004d081f20dd421ba5288766d56724c3b288ac')
>>> tx = Transaction(version=1,
... ins=[TxIn(txid='1a5a4f9a0d34cfca187db4fe6a3316f46264984c4b4c9fdb582123815afd508f',
... txout=0,
... script_sig=script_sig,
... sequence=Sequence.max())],
... outs=[TxOut(value=193000000,
... n=0,
... script_pubkey=script_pubkey)],
... locktime=Locktime(0))
>>> tx.txid
'14e6afbae7d2b1825b7ee711cbcad77d519767b70f5a1e70e5ba7f0bfc902e81'
Example creation of a SegWit transaction:
>>> from btcpy.structs.transaction import SegWitTransaction, Witness
>>> from btcpy.structs.script import StackData, empty_script
>>> witness_sig = StackData.from_bytes(unhexlify('304402200d0fbf48270e690be17cb0c47ee6ce2df3b671c2e4b196065e09c6df649b807c022056d8f10da83b2856458152c7f09e53a3495f3fbdd2e20638586a52ddff4f495b01'))
>>> witness_pubkey = StackData.from_bytes(unhexlify('02a079cb0269c933b1ee041a933092c9c439dd1b3a4eebd32ae391cf815002d378'))
>>> witness = Witness([witness_sig, witness_pubkey])
>>> script_pubkey = ScriptBuilder.identify('a914b2eb061810dac0614ac3e06d1bc55077b32b3b2687')
>>> tx = SegWitTransaction(version=1,
... ins=[TxIn(txid='1a5a4f9a0d34cfca187db4fe6a3316f46264984c4b4c9fdb582123815afd508f',
... txout=0,
... script_sig=empty_script,
... sequence=Sequence.max(),
... witness=witness],
... outs=[TxOut(value=193000000,
... n=0,
... script_pubkey=script_pubkey)],
... locktime=Locktime(0))
>>> tx.txid
'14dd31532ca06d62121fd13d35a2c9090246291960e73bf2bb3615abcb1bedab'
Of course, nobody would like to create transactions in such a cumbersome way. In fact,this library provides the appropriate tools to create complex scriptPubKeys in an easyfashion and to automatically fill in scriptSigs and witnesses of a spending transactionbased on the minimum needed parameters. In the following sections we will show someexamples of these features.
The supported scripts can be created by using their constructor and passing them theneeded parameters. They can be found in btcpy.structs.script. All the constructors of these classes can take an input of type Script.In this case they try to match it to their template and raise a WrongScriptTypeExceptionif the script does not match the desired template. Otherwise, they take the followingparameters:
| Class | Description | Parameters |
|---|---|---|
P2pkhScript, P2wpkhScript |
A P2PKH/P2WPKH script | Either a PublickKey, a bytearray representing a public key hash or an Address |
P2shScript |
A P2SH script | Either a ScriptPubKey representing the redeemScript, a bytearray representing the redeemScript's hash or an Address |
P2wshScript |
A P2WSH script | Either a ScriptPubKey representing the witnessScript, a bytearray representing the witnessScript's hash or an Address |
P2pkScript |
A P2PK script | A PublicKey |
NulldataScript |
An OP_RETURN script | A StackData representing the data to store in the transaction |
MultisigScript |
A multisig script, where m out of n keys are needed to spend | m, the number of signatures needed to spend this output, an arbitrary number of PublicKeys, n the number of public keys provided |
IfElseScript |
A script consisting of an OP_IF, a script, an OP_ELSE, another script and an OP_ENDIF |
Two ScriptPubKey scripts, the first to be executed in the if branch, the second to be executed in the else branch |
AbsoluteTimelockScript |
A script consisting of <pushdata> OP_CHECKLOCKTIMEVERIFY OP_DROP and a subsequent script which can be spent only after the absolute time expressed by the <pushdata> is expired |
A Locktime, expressing the absolute time/number of blocks after which the subsequent script can be spent, and the locked ScriptPubKey |
RelativeTimelockScript |
A script consisting of <pushdata> OP_CHECKSEQUENCEVERIFY OP_DROP and a subsequent script which can be spent only after the relative time time expressed by the <pushdata> is expired |
A Sequence, expressing the relative time/ number of blocks after which the subsequent script can be spent, and the locked ScriptPubKey |
Hashlock256Script |
A script consisting of OP_HASH256 <pushdata> OP_EQUALVERIFY and a subsequent script which can be spent only after providing the preimage of <pushdata> for the double SHA256 hash function |
Either a bytearray or StackData representing the hashed value that locks the subsequent script, plus the locked ScriptPubKey |
Hashlock160Script |
A script consisting of OP_HASH160 <pushdata> OP_EQUALVERIFY and a subsequent script which can be spent only after providing the preimage of <pushdata> for the RIPEMPD160 of the SHA256 hash function |
Either a bytearray or StackData representing the hashed value that locks the subsequent script, plus the locked ScriptPubKey |
Please note that in the following sections we will frequently use the same keypair for ease ofdocumenting, of course this is a very bad practice in a production environmentand should be avoided at all costs.
Spending a transaction
This library offers Solvers to spend a previous transaction's output. Solvers can be found in btcpy.structs.sig andexpect as input all the data needed to create the appropriate scriptSig and witness.To create a Solver, the Sighash class is needed. This class represents a SIGHASHand its constructor takes two parameters:
sighash, either of the literal strings'ONE','ALL'or'NONE'anyonecanpay, a flag defaulting toFalse.
The following solvers take one sighash as last parameter, defaulting to Sighash('ALL'):
P2pkhSolverP2wpkhV0SolverP2pkSolver
The MultisigSolver class takes many sighashes as additional last parameters, alldefaulting to Sighash('ALL'). All other classes do not accept sighashes.
Additionally, the following solvers are available and they take the following inputs:
| Class | Inputs | Solves |
|---|---|---|
P2pkhSolver |
a PrivateKey |
P2pkhScript |
P2wpkhV0Solver |
a PrivateKey |
P2wpkhV0Script |
P2pkSolver |
a PrivateKey |
P2pkhScript |
P2shSolver |
a ScriptPubKey, representing the redeemScript and a Solver which solves the redeemScript |
P2shScript |
P2wshV0Solver |
a ScriptPubKey, representing the witnessScript and a Solver which solves the inner witnessScript |
P2wshV0Script |
MultisigSolver |
an arbitrary number of PrivateKeys |
MultisigScript |
IfElseSolver |
an object of type Branch. This is an enum and its values are Branch.IF and Branch.ELSE, these are used to specify whether we are spending the if or else branch of the script. The second parameter is a Solver for the script inside the desired branch. |
IfElseScript |
TimelockSolver |
a Solver of the inner timelocked script |
AbsoluteTimelockScript, RelativeTimelockScript |
RelativeTimelockSolver |
a Solver of the inner timelocked script, with relative timelocks |
RelativeTimelockScript |
AbsoluteTimelockSolver |
a Solver of the inner timelocked script, with absolute timelocks |
AbsoluteTimelockScript |
HashlockSolver |
the preimage needed to spend the script, as a bytearray, and a Solver for the hashlocked script |
Hashlock256Script, Hashlock160Script |
To spend a previous transaction, the MutableTransaction class provides the spend() method.The spend() method expects the following inputs:
txouts, an array ofTxOuts being spent by the transaction's inputs, in the correctorder.solvers, an array ofSolvers, one per input, in the correct order
for example:
>>> from btcpy.structs.sig import *
>>> to_spend = Transaction.unhexlify('...')
>>> unsigned = MutableTransction(version=1,
... ins=[TxIn(txid=to_spend.txid,
... txout=0,
... script_sig=ScriptSig.empty(),
... sequence=Sequence.max())],
... outs=[TxOut(value=100000,
... n=0,
... script_pubkey=P2pkhScript(pubk))],
... locktime=Locktime(0))
>>> solver = P2pkhSolver(privk)
>>> signed = unsigned.spend([to_spend.outs[0]], [solver])
In particular, the spend() method automatically recognises whether we are spending a SegWit transaction,hence returning either a Transaction or a SegWitTransaction.
Now, let's see how more complex scripts can be created and spent. In the following examples, in solvers,we will always use the default SIGHASH_ALL, to change this, as described above, one can use thelast parameter of the solvers that accept SIGHASHes.
P2PKH
This is how a P2PKH script can be created:
# create public key
>>> pubk = PublicKey.unhexlify('025f628d7a11ace2a6379119a778240cb70d6e720750416bb36f824514fbe88260')
# create P2PKH script
>>> p2pkh_script = P2pkhScript(pubk)
>>> p2pkh_script.hexlify()
'76a914905f77004d081f20dd421ba5288766d56724c3b288ac'
>>> str(p2pkh_script)
'OP_DUP OP_HASH160 905f77004d081f20dd421ba5288766d56724c3b2 OP_EQUALVERIFY OP_CHECKSIG'
and this is an example of a P2PKH solver:
>>> privk = PrivateKey.unhexlify('a12618ff6540dcd79bf68fda2faf0589b672e18b99a1ebcc32a40a67acdab608')
>>> p2pkh_solver = P2pkhSolver(privk)
now let's assume we have an unsigned mutable transaction, we will use this solver to fill in the transaction'sscriptSig:
>>> unsigned_tx = MutableTransaction(...)
>>> previous_txout = TxOut(value=1000, n=0, script_pubkey=p2pkh_script)
>>> signed_tx = unsigned_tx.spend([previous_txout], [p2pkh_solver])
P2SH
Creating a P2SH script that embeds a P2PKH script:
>>> p2sh_script = P2shScript(P2pkhScript(pubk))
>>> p2sh_script.hexlify()
'a914cd1ab43e7c01a08886fd0e699988d2f44c9c57cc87'
>>> str(p2sh_script)
'OP_HASH160 cd1ab43e7c01a08886fd0e699988d2f44c9c57cc OP_EQUAL'
A solver to spend it would be:
>>> privk = PrivateKey.unhexlify('a12618ff6540dcd79bf68fda2faf0589b672e18b99a1ebcc32a40a67acdab608')
>>> solver = P2shSolver(P2pkhScript(pubk), # the redeemScript
P2pkhSolver(privk)) # the redeemScript's solver
P2WSH
Creating a P2WSH script that embeds a P2PKH script:
>>> p2wsh_script = P2wshV0Script(P2pkhScript(pubk))
>>> p2wsh_script.hexlify()
'002058f04cd072784e9dede6821772a195cef65424f2e4957e14232e642bbbdf1aec'
>>> str(p2wsh_script)
'OP_0 58f04cd072784e9dede6821772a195cef65424f2e4957e14232e642bbbdf1aec'
Solving it:
>>> solver = P2wshV0Solver(P2pkhScript(pubk), # witness script
... P2pkhSolver(privk)) # witness script's solver
P2WSH-over-P2SH
Let's now create a P2SH scriptPubKey that embeds a P2WSH that, in turn, embedsa P2PKH:
>>> p2wsh_over_p2sh = P2shScript(P2wshV0Script(P2pkhScript(pubk)))
>>> p2wsh_over_p2sh.hexlify()
'a914efbd1b969b0e15e7a3dc9b1128e4cf493974e62187'
>>> str(p2wsh_over_p2sh)
'OP_HASH160 efbd1b969b0e15e7a3dc9b1128e4cf493974e621 OP_EQUAL'
>>> solver = P2shSolver(
... P2wshV0Script(P2pkhScript(pubk)), # redeemScript
... P2wshV0Solver( # redeemScript solver
... P2pkhScript(pubk), # witnessScript
... P2pkhSolver(privk) # witnessScript solver
... )
... )
P2PK
>>> p2pk_script = P2pkScript(pubk)
>>> p2pk_script.hexlify()
'21025f628d7a11ace2a6379119a778240cb70d6e720750416bb36f824514fbe88260ac'
>>> str(p2pk_script)
'025f628d7a11ace2a6379119a778240cb70d6e720750416bb36f824514fbe88260 OP_CHECKSIG'
>>> solver = P2pkSolver(privk)
Multisig
>>> privk2 = PrivateKey.unhexlify('710b464f020b676fd9ec3af28d014dec9c8582e6a9059731a3e14aa762527ae4')
>>> pubk2 = privk2.pub()
>>> multisig_script = MultisigScript(1, pubk, pubk2, 2) # a 1-of-2 multisig
>>> multisig_script.hexlify()
'5121025f628d7a11ace2a6379119a778240cb70d6e720750416bb36f824514fbe882602102a5f22a78db5c38eaa18f73390e82e000bd52ab84edbcb3ad9b4124460acaf5ee52ae'
>>> str(multisig_script)
'OP_1 025f628d7a11ace2a6379119a778240cb70d6e720750416bb36f824514fbe88260 02a5f22a78db5c38eaa18f73390e82e000bd52ab84edbcb3ad9b4124460acaf5ee OP_2 OP_CHECKMULTISIG'
>>> multisig_solver = MultisigSolver(privk) # this could potentially be passed a list of SIGHASHES in the end to use them when signing
As one will usually embed this in a P2SH format, this could be done as follows:
>>> p2sh_multisig = P2shScript(multisig_script)
>>> solver = P2shSolver(multisig_script, multisig_solver)
Timelocks, Hashlocks, IfElse
Now we are going to create a very complex output. This output can be spent in two ways:
- at any time, with two out of two signatures
- 5 blocks after it has entered a block, with only one signature.This script is hence composed of two possible execution flows: an
ifbranch andanelsebranch. Inside the first branch, a 2-of-2 multisig script can be found.Inside the second branch there is a timelocked script. Such a script has a time(a relative time in this case, expressed as aSequencenumber) and an inner script,which is the one that can be executed after the relative time has expired.We can create such a script in the following way:
>>> timelocked_multisig = IfElseScript(
... # if branch
... MultisigScript( # a multisig script, as above
... 2,
... pubk,
... pubk2,
... 2
... ),
... # else branch
... RelativeTimelockScript( # timelocked script
... Sequence(5), # expiration, 5 blocks
... P2pkhScript( # locked script
... pubk
... )
... )
... )
Let's see this script a bit more in depth:
>>> timelocked_multisig.type
'if{ multisig }else{ [relativetimelock] p2pkh }'
>>> str(timelocked_multisig)
'OP_IF OP_2 025f628d7a11ace2a6379119a778240cb70d6e720750416bb36f824514fbe88260 02a5f22a78db5c38eaa18f73390e82e000bd52ab84edbcb3ad9b4124460acaf5ee OP_2 OP_CHECKMULTISIG OP_ELSE OP_5 OP_CHECKSEQUENCEVERIFY OP_DROP OP_DUP OP_HASH160 905f77004d081f20dd421ba5288766d56724c3b2 OP_EQUALVERIFY OP_CHECKSIG OP_ENDIF'
>>> timelocked_multisig.if_script
MultisigScript(2, 025f628d7a11ace2a6379119a778240cb70d6e720750416bb36f824514fbe88260, 02a5f22a78db5c38eaa18f73390e82e000bd52ab84edbcb3ad9b4124460acaf5ee, 2)
>>> str(timelocked_multisig.if_script)
'OP_2 025f628d7a11ace2a6379119a778240cb70d6e720750416bb36f824514fbe88260 02a5f22a78db5c38eaa18f73390e82e000bd52ab84edbcb3ad9b4124460acaf5ee OP_2 OP_CHECKMULTISIG'
>>> timelocked_multisig.else_script
RelativeTimelockScript(5, OP_DUP OP_HASH160 905f77004d081f20dd421ba5288766d56724c3b2 OP_EQUALVERIFY OP_CHECKSIG)
>>> str(timelocked_multisig.else_script)
'OP_5 OP_CHECKSEQUENCEVERIFY OP_DROP OP_DUP OP_HASH160 905f77004d081f20dd421ba5288766d56724c3b2 OP_EQUALVERIFY OP_CHECKSIG'
>>> timelocked_multisig.else_script.locked_script
P2pkh(905f77004d081f20dd421ba5288766d56724c3b2)
>>> timelocked_multisig.else_script.locked_script.decompile()
'OP_DUP OP_HASH160 905f77004d081f20dd421ba5288766d56724c3b2 OP_EQUALVERIFY OP_CHECKSIG'
Let's write the solvers for this script:
>>> solver_if = IfElseSolver(Branch.IF, # branch selection
... MultisigSolver(privk, privk2)) # inner solver
>>> solver_else = IfElseSolver(Branch.ELSE,
... RelativeTimelockSolver(Sequence(5), P2pkhSolver(privk)))
Low-level signing
If one wants to sign a transaction by hand, instead of using solvers, one of the following procedures can be used:
- Manually writing the scriptSig (this can be seen in the Creating transactions section)
- Creating the scriptSig by computing and signing the digest of the transaction
Let's see an example of this last case:
>>> unsigned = MutableTransaction(...)
>>> digest = unsigned.get_digest(2, # the input to be signed
prev_script, # the previous script to spend (this is the redeem/witness script in case of P2SH/P2WSH ouputs)
sighash=Sighash('NONE', anyonecanpay=True)) # sighash: 0x02 | 0x80
>>> privk.sign(digest)
In case one wants to sign a SegWit digest for the transaction, the following can be done:
>>> unsigned = SegWitTransaction(...)
>>> digest = unsigned.get_segwit_digest(2, # the input to be signed
prev_script, # the previous script to spend (this is the redeem/witness script in case of P2SH/P2WSH ouputs)
prev_amount, # the amount of the output being spent
sighash=Sighash('NONE', anyonecanpay=True)) # sighash: 0x02 | 0x80
>>> privk.sign(digest)
Contributing and running tests
This library has two testing tools that can be found in the tests/ folder:
unit.py, this runs basic unit testingintegration.py, this runs tests of signed transactions, to do this, transactions are signed andsent to a Bitcoin Core node through thesendrawtransactioncommand.
To make sure these tests are using the code in the current repository and not a stale copy installedin a virtualenv or system wide, please make sure to run the following commands from the root of therepo:
python3 -m unittest tests/unit.py
python3 -m unittest tests/integration.py
Contributors are invited to run these tests before submitting PRs. Also, contributions to improve andexpand these tests are highly welcome.
Roadmap to v1
This library's stable version 1 will be released once the following changes are made:
- More efficient script matching (i.e. scripts should be able to specify fast matching conditionsinstead of trying to parse the raw bytes to decide whether the template is matched)
- Caching on SegWit digest computation to avoid quadratic hashing
- Generation of private keys through secure entropy sources
- An extensive documentation of all modules, classes and their parameters is produced
TODO
Since this library is still a work in progress, the following roadmap lists the improvements to bedone eventually:
- Expanding the test suites
- Adding docstrings where missing (many places)
- Handling
OP_CODESEPARATORs in the signing process - Add further transaction creation helpers
- Add RPC calls to Bitcoin Core nodes
- Add networking with Bitcoin Core nodes
Acknowledgements
Special thanks to gdecicco and lorenzogiustfor contributing with performance improvements and general review.