Fwd: Re: Question for app developers, like Enigmail etc. - Identicons

Daniel Kahn Gillmor dkg at fifthhorseman.net
Mon Jun 5 22:26:56 CEST 2017

On Mon 2017-06-05 16:22:26 +0200, Stefan Claas wrote:
>>  * in the "distinguishing" model, it's not clear that any of the schemes
>>    i've seen are actually better for most humans against a dedicated
>>    attacker who crafts fingerprints to make visual identities that look
>>    similar.  do you have any studies showing this capability against a
>>    motivated and technically capable attacker?
> No, of course i have not. My thoughts as a not so-skilled GnuPG user
> would be that it helps users detecting (assuming it's bullet-proof)

what does "bullet-proof" mean, specifically?  I ask this not for
pedantry's sake, but because clearly stating the problem makes it
possible to know whether a specific solution is applicable.

> a proper key from a fake key more easily if they have not yet signed
> (locally) a public key while they already exchanged a couple of
> emails.  I can speak only of Thunderbird/Enigmail wich i use now. It
> gives a user the usual "Untrusted Good Signatur" and i have to click
> also on the Details button to carefully verify the fingerprint from an
> addional list to see if the key belongs to the person the signature
> claims. An additional visual fingerprint would make that proccess for
> me easier, if it's bullet-proof.

It sounds to me like you're saying that you find the key verification
and certification steps as implemented by enigmail to be
difficult-to-use.  You wouldn't be the only person who has that

But i don't see how a graphical icon solves that problem.  Isn't it a
workflow problem, and not a visual-comparison problem?  If there's a
standard thing (comparison, lookup, verification) you expect to be able
to do with the tool, the tool should make that thing easy and simple to

What specifically is the thing that you're trying to do when you click
"Details" and verify the fingerprint (from what list?)?  Enigmail itself
can compare fingerprints far better than you or i can, even if there is
a graphical representation involved :) Maybe there's a different
question or different interface Enigmail ought to offer in the "Details"
view entirely?

>> I'd generally think that if you're looking for a tool to help people
>> remember and recognize keys that they've seen before, then a mail user
>> agent is in a great position to do exactly that: just tell the user
>> explicitly what they've seen before, how often, etc.  why depend on the
>> human visual cortex or on human ability for numeric recall?
> I could imagine that Joe user average may not always look at mail headers
> very carefully for a little typo in the from: or reply-to: header in his
> mail client or web-mailer.

i agree with you that users won't look at mail headers closely, which is
why the e-mail client (the "mail user agent", or MUA) should be the
thing to do the comparison, and to make it very clear to the user when
something is amiss.  But that still doesn't answer the question of what
the MUA should actually be trying to compare and what results it should
be highlighting.

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