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[BIP-119] Better Explain AnyPrevout v.s. CTV

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Jeremy Rubin 2021-10-15 11:40:05 -07:00
parent 8364e25ebc
commit 27466fa815
1 changed files with 21 additions and 10 deletions
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@ -518,17 +518,28 @@ something similar to templates, via a scriptPubKey like:
<sig of desired TX with PK and fixed nonce R || SIGHASH_ANYPREVOUTANYSCRIPT <PK with public SK> OP_CHECKSIG
SIGHASH_ANYPREVOUTANYSCRIPT bears additional technical and implementation risks that may preclude
its viability for inclusion in Bitcoin, but the capabilities above are similar to what
CHECKTEMPLATEVERIFY offers. However, CHECKTEMPLATEVERIFY has benefits in terms of verification
speed, as it requires only hash computation rather than signature operations. This can be
significant when constructing large payment trees or programmatic compilations. CHECKTEMPLATEVERIFY
also has a feature-wise benefit in that it provides a robust pathway for future template upgrades.
SIGHASH_ANYPREVOUTANYSCRIPT bears additional technical and implementation risks
that may preclude its viability for inclusion in Bitcoin, but the capabilities
above are similar to what CHECKTEMPLATEVERIFY offers. The key functional
difference between SIGHASH_ANYPREVOUTANYSCRIPT and OP_CHECKTEMPLATEVERIFY is
that OP_CHECKTEMPLATEVERIFY restricts the number of additional inputs and
precludes dynamically determined change outputs while
SIGHASH_ANYPREVOUTANYSCRIPT can be combined with SIGHASH_SINGLE or
SIGHASH_ANYONECANPAY. For the additional inputs, OP_CHECKTEMPLATEVERIFY also
commits to the scriptsig and sequence, which allows for specifying specific P2SH
scripts (or segwit v0 P2SH) which have some use cases. Furthermore,
CHECKTEMPLATEVERIFY has benefits in terms of script size (depending on choice of
PK, SIGHASH_ANYPREVOUTANYSCRIPT may use about 2x-3x the bytes) and verification
speed, as OP_CHECKTEMPLATEVERIFY requires only hash computation rather than
signature operations. This can be significant when constructing large payment
trees or programmatic compilations. CHECKTEMPLATEVERIFY also has a feature-wise
benefit in that it provides a robust pathway for future template upgrades.
CHECKSIGFROMSTACK along with OP_CAT may also be used to emulate CHECKTEMPLATEVERIFY. However such
constructions are more complicated to use than CHECKTEMPLATEVERIFY, and encumbers additional
verification overhead absent from CHECKTEMPLATEVERIFY. These types of covenants also bear similar
potential recursion issues to OP_COV which make it unlikely for inclusion in Bitcoin.
CHECKSIGFROMSTACK along with OP_CAT may also be used to emulate
CHECKTEMPLATEVERIFY. However such constructions are more complicated to use
than CHECKTEMPLATEVERIFY, and encumbers additional verification overhead absent
from CHECKTEMPLATEVERIFY. These types of covenants also bear similar potential
recursion issues to OP_COV which make it unlikely for inclusion in Bitcoin.
Given the simplicity of this approach to implement and analyze, and the benefits realizable by user