BIP-373: denote different public key types/purposes consistently #1705
Conversation
Improve the clarity of the BIP w.r.t. pubkeys in the following ways:
- be specific about the purpose of pubkey types in PSBT fields
("plain pubkey" alone doesn't say a lot, especially if it's used
repeatedly within a field)
- replace all uses of "compressed pubkey" by "plain pubkey"
(the only category that should matter is whether the pubkey type
is "x-only" or "plain"; in the latter case, it's obvious from
the size of 33 bytes that the key is compressed)
- use consistent word order, e.g. prefer
"plain aggregate public key" over "aggregate plain public key"
theStack
force-pushed
the
bip373_improve_pubkey_clarity
branch
from
3c53392
to
953e807
Compare
I find the term "compressed" more clear than "plain", so I don't think that part of the change is an improvement. Similarly I find "compressed" vs "x-only" easier to understand than "plain 33 bytes" vs "x-only". I would just change: "Why the plain aggregate public key instead of x-only?" to say "compressed". |
| @@ -46,53 +46,53 @@ The new per-input types are defined as follows: | |||
| | rowspan="2"|MuSig2 Participant Public Keys | |||
| | rowspan="2"|<tt>PSBT_IN_MUSIG2_PARTICIPANT_PUBKEYS = 0x1a</tt> | |||
| | <tt><33 byte plain aggregate pubkey></tt> | |||
| | <tt><33 byte compressed pubkey>*</tt> | |||
| | <tt><33 byte plain participant pubkey>*</tt> | |||
There was a problem hiding this comment.
Could also say "33 byte participant pubkey (compressed)"
| | rowspan="2"| | ||
| | rowspan="2"| | ||
| | rowspan="2"| 0, 2 | ||
| |- | ||
| | The MuSig2 aggregate plain public key<ref>'''Why the plain aggregate public key instead of x-only?''' | ||
| | The MuSig2 plain aggregate public key<ref>'''Why the plain aggregate public key instead of x-only?''' |
There was a problem hiding this comment.
Maybe "The MuSig2 aggregate public key (compressed)"
| BIP 32 requires public keys to include their evenness byte. Aggregate public keys are expected to be | ||
| derived from, following [[bip-0328.mediawiki|BIP 328]], and therefore will | ||
| need to include the evenness. Furthermore, PSBT_IN_TAP_BIP32_DERIVATION fields include fingerprints | ||
| to identify master keys, and these fingerprints require full compressed public keys. By including | ||
| to identify master keys, and these fingerprints require full plain public keys. By including |
There was a problem hiding this comment.
require the y-coordinate of the public key, so x-only serialisation can't be used.
I think more important than the concrete term is to stick to one and use it consistently, so I'm also fine with changing all occurences to "compressed" if there are no objections. My impression was that "compressed" is significantly less used now than it was in the past (when there was only 65 vs. 33 bytes), especially since x-only pubkeys could then be seen as "even more compressed" 😅 // EDIT: slightly off-topic for the BIP repo here, but if we change everything to "compressed", the RPC help for |
That's true, but there's no other word for x-inclusive key. |
While reviewing bitcoin/bitcoin#31247 a while ago I noticed that the mentioned public keys in the PSBT fields of this BIP are quite confusing. This is mostly due to a non-consistent mention of types (plain vs. x-only) and a purpose that is sometimes missing. This PR aims to improve this in the following ways:
Another possibility would be to even get rid of the "plain" terminology completely. From the fact that "x-only" is not explicitly mentioned and the size of 33 bytes it should be obvious that this is a plain public key.