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Re: [openpgp] Should fingerprints be "key-canonical"?

Daniel Kahn Gillmor <dkg@fifthhorseman.net> Sat, 09 April 2016 03:15 UTC

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From: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
To: Jon Callas <jon@callas.org>, Bryan Ford <brynosaurus@gmail.com>
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Date: Sat, 09 Apr 2016 00:15:14 -0300
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Cc: openpgp@ietf.org, Jon Callas <jon@callas.org>
Subject: Re: [openpgp] Should fingerprints be "key-canonical"?
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On Thu 2016-04-07 20:33:56 -0300, Jon Callas <jon@callas.org> wrote:
>   Yes, because I can tell you that it's *really* useful to be able to
>   reuse the key material from alice@example.com for (e.g.)
>   jobs@example.com or security, or whatever. I've done it a lot over
>   the years.

What is the utility here, specifically?

I appreciate making tracking/linkability harder as a goal, but i'm not
conivnced that this achieves that purpose.

Anyone who has the keys for alice@example.com and jobs@example.com can
tell that these are the same keys, and can just join them in their
linkability/trackability database.

Furthermore, it introduces additional management problems for Alice; if
she loses control of the secret key material, she now has to ensure that
she's generated a revocation certificate for each "flavor" of it,
because the revocations are bound to the same material that the
fingerprint is bound to.

If the revocation were bound to the public key material, then Alice
could revoke once and be done with it.

New keys are cheap enough that Alice should be able to solve the
linkability problem y just having an entirely separate key for
jobs@example.com, no?

      --dkg

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