Adding bech32 spending example #73

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1. dgpv commented on Aug 31, 2022

   

   dgpv

   on Aug 31, 2022

   Last edited by dgpv

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   You can look into python-elementstx examples for the code that spends p2wsh address: https://github.com/Simplexum/python-elementstx/blob/4858587d27c9cdc16eb4d1556f95be33e7406abe/examples/confidential-cross-chain-atomic-swap.py#L602-L646

   or look into implementation of PartiallySignedTransaction.sign() - it has code that signs various types of inputs.

   more example code is of course welcome if you or anyone are willing to create that.
2. mrx23dot commented on Aug 31, 2022

   

   mrx23dot

   on Aug 31, 2022

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   Thank you, I will give it a go.
3. mrx23dot commented on Sep 3, 2022

   

   mrx23dot

   on Sep 3, 2022

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   Some minimal help would be appreciated, all I'm trying to do is transfer from bc1xx to bc1xx.

   No idea what to do with these, big example mentions 3 alice,bob and contract keys.

     spend_key=None # from privkeyBytes parameter ?
     btc_contract='?'
   

   I guess branch_condition true is to not to use lock times.
   Do we know the numof vBytes in advance to calculate the fee?

   This is what I have:

   from bitcointx.wallet import CCoinAddress
   from bitcointx.core import CMutableTransaction,CTxIn, CTxOut,COutPoint,lx,CTxInWitness
   from bitcointx.core.script import SIGHASH_ALL,SIGVERSION_WITNESS_V0, DATA,CScriptWitness,CBitcoinScript
   
   def sweep_bech32_tx(utxos, toAddrStr, privkeyB, feeSat=200):
   
     spend_key=None # from privkeyB parameter ?
     btc_contract='?'
   
     in_amount = sum([amntSat for txid,vout_n,amntSat in utxos])
     out_amount = in_amount - feeSat
   
     # Create the unsigned transaction.
     tx = CMutableTransaction(
       vin=[CTxIn(prevout=COutPoint(hash=lx(txid), n=vout_n)) for txid,vout_n,amntSat in utxos],
   
       vout=[CTxOut(nValue=out_amount, scriptPubKey=CCoinAddress(toAddrStr).to_scriptPubKey())]
     )
     cond = b'\x01' # branch_condition true
     # We used P2WSHCoinAddress to create the address that we sent bitcoin to, so we know that we need to use SIGVERSION_WITNESS_V0
     sighash = btc_contract.sighash(tx, 0, SIGHASH_ALL, amount=in_amount, sigversion=SIGVERSION_WITNESS_V0)
     spend_sig = spend_key.sign(sighash) + bytes([SIGHASH_ALL])
     # This is script witness, not script. The condition for OP_IF
     # in our script is directly encoded as data in the witness.
     # We cannot use OP_TRUE/OP_FALSE here. We use DATA guard is to ensure that.
     witness = CScriptWitness([spend_sig, DATA(cond), btc_contract])
     # empty scriptSig, because segwit
     tx.vin[0].scriptSig = CBitcoinScript([])
     # all data to check the spend conditions is in the witness
     tx.wit.vtxinwit[0] = CTxInWitness(witness)
     # VerifyScript not working
     return tx
   
   # inputs: (txid, vout_n, amntSat)
   utxos = [
     ('097fed228b1c4afb9dc8df2ae137e4be5e1c1376541c2db3b1c74a6166e7842b', 0, 178876), 
   ]
   tx = sweep_bech32_tx(utxos, toAddrStr='bc1..', privkeyB=bytes.fromhex('11'*32))
   print(tx) 
   
   
4. dgpv commented on Sep 5, 2022

   

   dgpv

   on Sep 5, 2022

   Last edited by dgpv

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   Hmm, I guess linking to python-elementstx example was not helpful, because that example uses custom bitcoin scripts and that is not the same as signing simple keypath spending.

   You probably better use PartiallySignedTransaction's sign() method, you can create psbt from CTransaction like in this test code: https://github.com/Simplexum/python-bitcointx/blob/master/bitcointx/tests/test_psbt.py#L401 and then call psbt.sign(keystore) where keystore is an instance of KeyStore which contains your keys