Re: [perpass] Getting started...

Ben Laurie <benl@google.com> Sat, 17 August 2013 12:04 UTC

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Date: Sat, 17 Aug 2013 08:04:24 -0400
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From: Ben Laurie <benl@google.com>
To: Stephen Farrell <stephen.farrell@cs.tcd.ie>
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Subject: Re: [perpass] Getting started...
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On 17 August 2013 07:52, Stephen Farrell <stephen.farrell@cs.tcd.ie> wrote:

>
> Hi Ben,
>
> On 08/17/2013 12:37 PM, Ben Laurie wrote:
> > On 16 August 2013 12:42, Stephen Farrell <stephen.farrell@cs.tcd.ie>
> wrote:
> >
> >> what should we be doing?
> >
> >
> > Certificate Transparency is an anti-monitoring tool, amongst other useful
> > properties.
>
> Yep. Its a fine tool but more I guess directed at countering
> an active attacker who spoofs as a web site and then monitors
> or snarfs passwords or whatever.
>
> > The more generalised idea of a public, verifiable log of stuff is
> probably
> > useful in other ways, too.
> >
> > For example, DNSSEC Transparency (OK, hardly much different from CT).
> >
> > Someone mentioned default encrypting emails: sparse Merkle trees are an
> > efficient data structure for making a verifiable map of email addresses
> to
> > public keys...
>
> neat idea... maybe.
>
> However, that and other foo-transparency ideas also require
> clients to ask the log about stuff, in a way that the log
> can.... log.
>

So, Private Information Retrieval is a way around this issue. I don't know
much about it, yet, but I'm told its fairly expensive. But I think not too
expensive for this kind of operation.

As it happens, I am planning to do some work with Ian Goldberg on the
subject, and so will have more to say about it in a while.

Also, it may be that simply retrieving the whole log is feasible. We're not
talking about vast amounts of data.


>
> For CT, thats ok since the web site itself (or its
> auditors) can contact the CT log, but I wonder if that'd
> become a problem for other foo-transparency applications,
> e.g. how could an MUA query a log of public keys without
> exposing the meta-data that I'm sending you an encrypted
> message?
>

I would observe that you already reveal that, unless you come up with some
entirely novel way of delivering email. I am not suggesting that this means
the problem should not be solved, but it seems that encrypting the payload
routinely moves the needle a fair amount - enough to be worth doing while
we figure out the whole thing.


>
> > Yes, I have a hammer and I am looking for nails.
>
> :-)
>
> S.
>
> >
> >
> >
> > _______________________________________________
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> >
>