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Jan 23, 2021 at 18:26 history edited Claris CC BY-SA 4.0
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Feb 9, 2017 at 22:53 comment added Nick ODell That would be a reasonable solution, and it would work well in most cases. However, 143 allows ANYONECANPAY and SINGLE, which wouldn't work if only hashing once.
Feb 9, 2017 at 22:43 comment added pinhead Right so why not add a OP_CHECKSIG2 and new tx/address type as a soft fork that hashes the whole tx minus sigs one time and uses that hash for each input?
Feb 9, 2017 at 22:36 comment added Nick ODell That's only for OP_CHECKSIG, correct. The new opcode is a data push of one byte of 0 to 16.
Feb 9, 2017 at 22:31 comment added pinhead But it's only critical to consensus for OP_CHECKSIG right? What if there was just a new op code that signed differently?
Feb 9, 2017 at 22:28 comment added Nick ODell Because each hash is hashing something slightly different. The references of BIP143 go into more detail about this, but you should especially look at en.bitcoin.it/wiki/OP_CHECKSIG TL;DR: the input you're signing for has a part of the scriptPubKey of the previous transaction in it. This is consensus-critical; changing it requires a hardfork or the creation of a new way of signing transactions.
Feb 9, 2017 at 21:47 comment added pinhead I understand that signatures can't be signed, I guess I don't know why the hash for each input Sig is different? If all sigs are removed prior to hashing, why isn't the whole blob hashed just once for the entire transaction?
Feb 9, 2017 at 20:35 history answered Nick ODell CC BY-SA 3.0