SegwitAddress: allow instantiation of P2A (pay-to-anchor) address #3542
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Hi! 🙂
Overview
As you may remember, in pullrequest #2663, I introduced a length check for the witness programs of v1 addresses, allowing only 32-byte long programs. Reviewing our discussion from back then, we decided to merge this check even though, according to BIP 341, such v1 witness programs aren’t prohibited. Instead, they produce "anyone-can-spend" outputs (per consensus rules).
Additionally spending from these outputs is disallowed by policy (non-standard), so we came to the conclusion that it probably might not make sense to instantiate such
SegwitAddress(especially when bitcoinJ is used in the context of a client).Change in this PR
In this PR, I’ve relaxed the restriction slightly to permit one specific v1 witness program shorter than 32 bytes: the P2A (pay-to-anchor) output script.
A P2A output script is a segwit output with a witness version of
1and a hardcoded witness program of[0x4e, 0x73].You can find the definition of this output type here in Bitcoin Core. Since the merge of bitcoin/bitcoin#30352 (released in 28.0) spending from this specific output script is now allowed by policy.
Rationale
Following our discussion when we introduced the taproot witness program length check in #2663, where we talked that bitcoinJ should follow policy, and the fact that spending from P2A is now allowed by policy, I allowed creation of this address.
References