Topic: finding TxHash to verify a Tx (Read 653 times)

OP_CODESEPARATOR isn't something you will encounter a lot of.

Normally you can just copy the txOut's script directly (SCRIPT_PART4) when making txCopy (when you drop the scriptPubKey into the scriptSig of the input), but if OP_CODSEPARATOR is used, you only copy the script following it.

In order to verify a transaction, I want to make sure that I have the correct value
for the double hash of the TxCopy  (the transaction hash used to sign and verify a transaction).

I used http://www.righto.com/2014/02/bitcoins-hard-way-using-raw-bitcoin.html
for the final transaction and
https://en.bitcoin.it/w/images/en/7/70/Bitcoin_OpCheckSig_InDetail.png"
to find TxCopy from finalTx.

from finalTx:

There is just 1 input:
prevOutputHashReverse = 484d40d45b9ea0d652fca8258ab7caa42541eb52975857f96fb50cd732c8b481
prevOutputHash            = 81b4c832d70cb56ff957589752eb4125a4cab78a25a8fc52d6a09e5bd4404d48
prevOutputIndex           = 00000000

from prevOutputHash and prevOutputIndex, I can get the prevOutput:

prevOutput = 728b0100000000001976a914df3bd30160e6c6145baaf2c88a8844c13a00d1d588ac

from prevOutput, I get

prevOutputScriptPubKey = 76a914df3bd30160e6c6145baaf2c88a8844c13a00d1d588ac

now I can construct the txCopy
this only differences with finalTx are steps e, f and k

NOTE: in https://en.bitcoin.it/w/images/en/7/70/Bitcoin_OpCheckSig_InDetail.png
step 2, there is an instruction: "if no OP_CS, simply copy PKScript" (=prevOutputScriptPubKey)
I don't know what to do with those OP_CODE_SEPARATOR !
Should I copy PKScript or not? What SCRIPT_PART4 should be?
If I copy PKScript, does it mean SCRIPT_PART4 = PKScript?
If yes: step e below becomes 32 and step f becomes (PKScript | PKScript) =
76a914df3bd30160e6c6145baaf2c88a8844c13a00d1d588ac76a914df3bd30160e6c6145baaf2c 88a8844c13a00d1d588ac

with SCRIPT_PART4 empty:

a) version                          = 01000000
b) input count                    = 01
c) prevOutputHashReverse  = 484d40d45b9ea0d652fca8258ab7caa42541eb52975857f96fb50cd732c8b481
d) preOutputIndex              = 00000000
e) prevOutputScriptPubKeyLength = 19
f) prevOutputScriptPubKey  = 76a914df3bd30160e6c6145baaf2c88a8844c13a00d1d588ac
g) sequence                       = ffffffff
h) outputCount                   = 01
i) output00                         = 62640100000000001976a914c8e90996c7c6080ee06284600c684ed904d14c5c88ac
j) lockTime                         = 00000000
k) hashTypeCode                = 01000000      (little-endian)

txCopy = 0100000001484d40d45b9ea0d652fca8258ab7caa42541eb52975857f96fb50cd732c8b48100000 0001976a914df3bd30160e6c6145baaf2c88a8844c13a00d1d588ac
ffffffff0162640100000000001976a914c8e90996c7c6080ee06284600c684ed904d14c5c88ac0 000000001000000

SHA256(SHA256(txCopy)) = 5FDA68729A6312E17E641E9A49FAC2A4A6A680126610AF573CAAB270D232F850

Can somebody tells me if it's the correct value ?

if SCRIPT_PART4 = PKScript:
SHA256(SHA256(txCopy)) = 488A0FCF5FCBF4119E9595F029060D31CE97DC0A9C5594B9A3D7E914B5B268BE