Re: [MLS] Group ID
Richard Barnes <rlb@ipv.sx> Wed, 05 June 2019 20:30 UTC
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From: Richard Barnes <rlb@ipv.sx>
Date: Wed, 05 Jun 2019 13:29:58 -0700
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To: Raphael Robert <raphael=40wire.com@dmarc.ietf.org>
Cc: Messaging Layer Security WG <mls@ietf.org>, Marek Jankowski <mjankowski309@gmail.com>
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Subject: Re: [MLS] Group ID
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Sorry, hit "send" prematurely. On Wed, Jun 5, 2019 at 1:29 PM Richard Barnes <rlb@ipv.sx> wrote: > Like Raphael, I'm not concerned about the ordering requirement, since we > already have an ordering requirement. Note, however, that whatever > identifier is used here will probably have to be stable within an epoch, so > the DS will still be able to see traffic volumes within an epoch. The DS > may also be able to use time correlations to infer which opaque groupID > values represent the same group. > > That still seems like it makes it harder for the DS to be malicious, so it > seems worthwhile to me. Benjamin Beurdouche had raised a similar idea > earlier, of replacing the (groupID, epoch) pair with a single ID that is > opaque to the DS. I'm increasingly thinking that that's probably the way > to go. Marek / Benjamin, if you'd like to update PR#152 to do this, that > could help move this along. > https://github.com/mlswg/mls-protocol/pull/152 I wonder if we still want some constant group ID value, even if it's known > only to group members. No concrete > ... need is occurring to me right now, but it seems like there might be some utility in separating contexts. --Richard > > > On Wed, Jun 5, 2019 at 1:00 AM Raphael Robert <raphael= > 40wire.com@dmarc.ietf.org> wrote: > >> Hi Marek, >> >> > I am aware it does not support reordering, But I'm sure one can figure >> an alternative that does. >> >> We looked into doing exactly that. Server-side ordering is unfortunately >> a hard requirement for TreeKEM, so this is an open issue. We’d be happy to >> hear about a proposal that covers both problems! >> >> Raphael >> >> > On 11 Jun 2019, at 16:33, Marek Jankowski <mjankowski309@gmail.com> >> wrote: >> > >> > Hi, >> > Regarding some issues that were raised in the last couple of months, I >> wonder if we should hide the group ID from the DS. I think the group ID is >> valuable metadata -- the DS may keep track of it and by that identify >> sudden changes in the traffic, which may leak information. >> > Please consider the following alternatives: >> > group_id[n] = HKDF-Expand-Label(confirmation_key[n-1],group_id[n-1], >> "group_id", 4) >> > I am aware it does not support reordering, But I'm sure one can figure >> an alternative that does. >> > >> > Marek. >> > _______________________________________________ >> > MLS mailing list >> > MLS@ietf.org >> > https://www.ietf.org/mailman/listinfo/mls >> >> _______________________________________________ >> MLS mailing list >> MLS@ietf.org >> https://www.ietf.org/mailman/listinfo/mls >> >
- [MLS] Group ID Marek Jankowski
- Re: [MLS] Group ID Raphael Robert
- Re: [MLS] Group ID Richard Barnes
- Re: [MLS] Group ID Richard Barnes