Add BIP 370: PSBT Version 2 #1059
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Needs a backward compatibility section |
There's a Compatibility section. |
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Would be nice to have it named per BIP 2 Let's use BIP number 370 |
Done. |
| If the newly added input has an incompatible time lock, then it must not be added. | ||
| If it changes the transaction's locktime when there are existing signatures, it must not be added. | ||
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| If the Has SIGHASH_SINGLE flag is True, then the Constructor must iterate through the inputs and find the inputs which have signatures that use SIGHASH_SINGLE. |
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Incomplete sentence, If the PSBT_GLOBAL_TX_MODIFIABLE field has
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Has SIGHASH_SINGLE flag is the noun in this sentence.
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ACK b3d224f.
We will probably implement this in rust-bitcoin and cross check once we have test-vectors.
Previously these tests were using 0x0f as the unknown field number. As these have now been defined, change them to use 0xf0 instead as it is unlikely we will use those anything soon.
| The PSBT version number is set to 2. The transaction version number must be set to at least 2. <ref>'''Why does the transaction version number need to be at least 2?''' The transaction version number is part of the validation rules for some features such as OP_CHECKSEQUENCEVERIFY. Since it is backwards compatible, and there are other ways to disable those features (e.g. through sequence numbers), it is easier to require transactions be able to support these features than to try to negotiate the transaction version number.</ref> | ||
| The Creator should also set PSBT_GLOBAL_PREFERRED_LOCKTIME. | ||
| If the Creator is not also a Constructor and will be giving the PSBT to others to add inputs and outputs, the PSBT_GLOBAL_TX_MODIFIABLE field must be present and and the Inputs Modifiable and Outputs Modifiable flags set appropriately. | ||
| If the Creator is a Constructor and no inputs and outputs will be added by other entities, PSBT_GLOBAL_TX_MODIFIABLE may be omitted. |
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Should this also explicitly specify that if the no inputs/outputs will be modified(instead of added), then PSBT_GLOBAL_TX_MODIFIABLE can be omitted.
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No, because things like signatures will be added to the inputs, so you would expect them to be modified.
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What does "input modification" mean in the PSBT_GLOBAL_TX_MODIFIABLE flag? Does this mean don't touch any data apart from witness data? Is changing something like nSequence allowed?
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It just means that the inputs vector can be modified, i.e. new inputs added. In terms of an input or output being modified, anything can be changed except for the things that uniquely identify the input or output. This means that you can't change the previous txid and output index in an input, and you can't change the scriptpubkey or the amount in an output.
| | [[bip-psb2.mediawiki|psbt2]] | ||
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| | SIGHASH_SINGLE Inputs | ||
| | <tt>PSBT_GLOBAL_SIGHASH_SINGLE_INPUTS = 0x07</tt> |
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Post-merge coment: This field is not present in BIP370. Was it left here by mistake ? Or not added to BIP370 by mistake ?
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Oops, that should have been removed from 174.
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btw, if the BIP would require signers to add PSBT_IN_SIGHASH_TYPE if they used SIGHASH_SINGLE for the signature, and finalization to preserve PSBT_IN_SIGHASH_TYPE, then constructors could rely on this instead, and they would not need an interpreter. The problem would be older finalizers that can still remove this field, though. Was this bitmap planned to be used essentially for the same purpose ?
Adds a BIP specifying PSBT version 2, as discussed on the mailing list: https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2020-December/018300.html
This requires the formatting changes to BIP 174 to be merged first: #1055