Re: [openpgp] Privacy-preserving Transferable Public Keys
Vincent Breitmoser <look@my.amazin.horse> Sun, 16 June 2019 12:14 UTC
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Date: Sun, 16 Jun 2019 14:14:48 +0200
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From: Vincent Breitmoser <look@my.amazin.horse>
To: Werner Koch <wk@gnupg.org>
Cc: openpgp@ietf.org
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Subject: Re: [openpgp] Privacy-preserving Transferable Public Keys
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Hi Werner, thanks for your response! > > A) Distribute updates to subkeys and the primary key (expiry, revocation, etc), > > without revealing the key's UserIDs. > > Easy for new and revoked subkeys. Easy how? You mean by allowing import of subkeys from TPKs without user ids? I'm a bit confused here: in the patch series I submitted to GnuPG towards that effect, said you weren't happy with this approach and referred to this thread. Perhaps I misunderstood. > Right, direct key signatures can be used but I we have not much > experience with them. Agreed. There are a bunch of details that would have to be figured out for this approach. I hope we can agree though that the idea of per-userid preferences ("this user id prefers Twofish, this other one AES") causes more problems and inconsistencies than it is worth. > Why should one want to do that? The user id (i.e. mail address or DNS > name) is important meta data. User IDs have value when a key wants to publicly claim a designation, and this is necessary for WoT style workflows where people sign this binding. But this use case hasn't exactly stood the test of time. With key discovery mechanisms like Autocrypt or WKD (the future!), we don't really depend on user ids anymore. Clients that have domain knowledge of the context that keys are used in (e.g. email clients) can assign much more useful labels than openpgp implementations themselves. This isn't just theory: OpenKeychain and K-9 associate keys with email addresses from Autocrypt keys independently from user ids, and can even work without user ids altogether. Enigmail maintains a similar mapping, and it is a central part of the Autocrypt spec. Sequoia uses a "pet names" concept that works similarly. I also think this is basically what GnuPG does with its TOFU trust model, at least that's what the database structure looks like. All of that said, I don't want to push super hard towards getting rid of user ids right now, or even at all. Perhaps we never can get that far. But thinking about where we can reduce metadata that isn't strictly necessary is a good thing, so yes I would welcome if we converged in a direction that reduced our reliance on user ids a bit. Moving from user ids to direct key signatures is probably too difficult in terms of backwards compatibility. But "unstated user ids", as similarly suggested in the abuse-resistant-keyserver draft, could be a good compatible step in this direction. - V
- [openpgp] Privacy-preserving Transferable Public … Vincent Breitmoser
- [openpgp] Optional User IDs Neal H. Walfield
- Re: [openpgp] Privacy-preserving Transferable Pub… Heiko Stamer
- Re: [openpgp] Privacy-preserving Transferable Pub… Werner Koch
- Re: [openpgp] Privacy-preserving Transferable Pub… Vincent Breitmoser
- Re: [openpgp] Privacy-preserving Transferable Pub… Werner Koch
- Re: [openpgp] Privacy-preserving Transferable Pub… Vincent Breitmoser