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From: Jonas Schnelli <dev@jonasschnelli.ch>
To: Pieter Wuille <pieter.wuille@gmail.com>,
	Bitcoin Protocol Discussion
	<bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] BIP 174 thoughts
Date: Tue, 19 Jun 2018 11:38:24 +0200	[thread overview]
Message-ID: <011F22E3-0116-4769-88FB-0CB675E5BCD5@jonasschnelli.ch> (raw)
In-Reply-To: <CAPg+sBhGMxXatsyCAqeboQKH8ASSFAfiXzxyXR9UrNFnah5PPw@mail.gmail.com>

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> * Key-value map model or set model.
> * Ability for Combiners to verify two PSBT are for the same transaction
> * Optional signing
> * Derivation from xpub or fingerprint
> * Generic key offset derivation
> * Hex encoding?

I think all of Pieters points are valid and reasonable thought, though I’m unsure if it would be worth changing the existing-implementation-breaking things like the k/v set model.
AFAIK things like non-hex-encoding or generic key offset derivation are extensions and would not break existing implementations.

Further thoughts on BIP174 from my side.

Key derivation in multisig:
From my understanding, the signers and the creator must have agreed – in advance to the PSBT use case – on a key derivation scheme.
BIP32 derivation is assumed, but may not always be the case.
Sharing xpubs (the chaincode) may be a concern in non-trust-relationships between signer(s) and the creator (regarding Pieters xpub/fingerprint concerns).
Providing the type 0x03, the bip32 derivation path is one form of a support to faster (or computational possible) derivation of the required keys for signing a particular input.
From my point of view, it is a support of additional metadata shared between creator and signer and provided from the creator to the signer for faster (or computation possible) key deviation.

I think it could be more flexible (generic) in BIP174.
It could be just a single child key {32-bit int}, or just a keypath ({32-bit int}]{32-bit int}…) which is very likely sufficient for a HWW to derive the relevant key without the creation of a lookup-window or other „maps".
It could even be an enciphered payload which was shared during address/redeem-script generation and „loops“ back during a signing request.

Maybe I’m overcomplicating things, but for practical multisig with HWWs, a simple BIP32-child-key-index or BIP32-keypath derivation support field should be sufficient.
A generic „derivation support field“, provided from the signer to the creator during address-generation that just „loops“ back during the PSBT use-cases is probably a overkill.


Thanks
—
/jonas


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  parent reply	other threads:[~2018-06-19  9:38 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-15 23:34 [bitcoin-dev] BIP 174 thoughts Pieter Wuille
2018-06-16 15:00 ` Peter D. Gray
2018-06-19  9:38 ` Jonas Schnelli [this message]
2018-06-19 14:20 ` matejcik
2018-06-19 15:20   ` Jonas Schnelli
2018-06-21 20:28     ` Peter D. Gray
2018-06-19 17:16   ` Pieter Wuille
2018-06-21 11:29     ` matejcik
2018-06-21 17:39       ` Pieter Wuille
2018-06-21 11:44     ` Tomas Susanka
2018-06-19 14:22 ` matejcik
2018-06-21  0:39 ` Achow101
2018-06-21 14:32   ` Tomas Susanka
2018-06-21 15:40     ` Greg Sanders
2018-06-21 19:56     ` Peter D. Gray
2018-06-21 21:39       ` Gregory Maxwell
2018-06-22 19:10       ` Pieter Wuille
2018-06-22 22:28         ` Achow101
2018-06-23 17:00           ` William Casarin
2018-06-23 20:33             ` Andrew Chow
2018-06-24  8:19               ` Andrea
2018-06-24  8:28                 ` Andrew Chow
2018-06-24  9:00                   ` Andrea
2018-06-23 18:27           ` Peter D. Gray
2018-06-25 19:47           ` Tomas Susanka
2018-06-25 20:10             ` Jonas Schnelli
2018-06-25 20:30             ` Achow101
2018-06-26 15:33               ` matejcik
2018-06-26 16:58                 ` William Casarin
2018-06-26 17:11                   ` Marek Palatinus
2018-06-27 14:11                   ` matejcik
2018-06-26 20:30                 ` Pieter Wuille
2018-06-27 14:04                   ` matejcik
2018-06-27 15:06                     ` Pieter Wuille
2018-06-29  9:53                       ` matejcik
2018-06-29 19:12                         ` Achow101
2018-06-29 20:31                           ` Peter D. Gray
2018-07-04 13:19                           ` matejcik
2018-07-04 18:35                             ` Achow101
2018-07-05 17:23                               ` Jason Les
2018-07-04 19:09                             ` Pieter Wuille
2018-07-05 11:52                               ` matejcik
2018-07-05 22:06                                 ` Pieter Wuille
2018-07-10 12:10                                   ` matejcik
2018-07-11 18:27                                     ` Pieter Wuille
2018-07-11 20:05                                       ` Gregory Maxwell
2018-07-11 20:54                                         ` [bitcoin-dev] BIP 174 thoughts on graphics vv01f
2018-06-26 21:56                 ` [bitcoin-dev] BIP 174 thoughts Achow101
2018-06-27  6:09                   ` William Casarin
2018-06-27 13:39                     ` Andrea
2018-06-27 17:55                     ` Achow101
2018-06-28 20:42                       ` Rodolfo Novak
2018-07-05 19:20                       ` William Casarin
2018-07-06 18:59                         ` Achow101
2018-06-20  0:39 Jason Les

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