[Standards] XEP-0373: Retracting public keys

Philipp Hörist philipp at hoerist.com
Sat Jul 1 20:55:02 UTC 2017


As im working on a implementation on this, and coming from OMEMO, i noticed
that the case of retracting keys is not handled at all.

Questions that arise are:

Lets say i have a public key of one contact and my client goes online

1) what if i get no PEP event with a public key. does that mean anything?
how should we react?

2) what if i get a PEP event with a public key different to the one i was
using until now? should i untrust the not anymore distributed key?

OMEMO has the same use case, as it also distributes keys via PEP, i think
its also not exactly written down there, but over the time we have a
convention that goes as follows

No PEP event means nothing, we still encrypt to the valid keys we have.
This is because Server implementation of PEP are handling stuff differently
Some send only PEP events if the contacts are online
Some have no persistent PEP

So from the fact that we didnt receive a PEP event, we can conclude exactly
nothing, and certainly not that our contact wants to invalidate his
published key.

All public keys we have from a contact that are not in the PEP event we
just received are marked as untrusted immediately

any device that comes online has to test if the correct public key is
published, and if not, it must publish the correct one immediately.

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