Handling a TOFU conflict

[Werner Koch]

On Thu,  8 Dec 2016 22:11, neal at walfield.org said:

> A homographic attack is not an attack on TOFU; it is an attack on the
> user.  TOFU can help prevent such attacks.

Maybe a TOFU system can helper.  However, this is not for what we use
it.

> I agree that we want to use TOFU to provide weak authentication (i.e.,
> verify that entity X controls key Y).

TOFU means Trust on _First Use_ and that is what we need.  We trust the
mail address and its key on the first use and we want the TOFU code to
tell us about a conflict and help to resolve a possible conflict (i.e. a
a key with a mail address which is not legitimate).

> The difficult question is: how to we find an appropriate key for a
> given entity when we haven't verified the entity?  It is appealing to
> use TOFU, whose judgments are based on history, but this is a hack.

That is not the goal of TOFU.  To discover the key for a given address
we have other methods (DANE, WKD, signature verification).

> question: "If I want to send a message to bob at example.com what is the
> best key?"  How exactly this works is an implementation detail, but it

That is not the question.  There will only be one key for
bob at example.com.


Salam-Shalom,

   Werner

-- 
Die Gedanken sind frei.  Ausnahmen regelt ein Bundesgesetz.
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