Re: [Taler] Hello

[Jeff Burdges]

On Mon, 2016-12-05 at 17:45 +0100, Joerg Baach wrote:
> But the issuer/exchange would still get some information, e.g. if the
> merchant deposited a value of 6.8584, and somebody shows up wanting to
> refresh 3.1415, these two participants are somewhat likely to have
> participated in the same transaction. I know, TOR might help.

Yes, refresh can leak your IP address, but Tor is important for several
things anyways, like retrieving /keys.  

An idea for NFC payments is to use the merchant as a channel to do the
refresh, so that NFC devices can be used entirely offline, except  for
withdrawal operations.  We do not do this over the web for performance
reasons, but if maximal anonymity is desired then doing so might improve
things.

> Ok, so is it the customers responsibilty to find a way to link the
> merchants key to the legal entity of the merchant, or is it the exchange
> who signed the merchants key?

I believe Christian is offline this week, but Florian could answer this.
If he does not, then I can check the source.

A priori, I'd want the merchant key verified by a certificate authority
using X.509c, meaning it should be signed by the merchant's
certificate.*   

Jeff

* We could even transfer the merchant key in a TLS session and record
that whole session.  We should not however use their TLS key as the
merchant key, because doing so voids any proofs of security for TLS and
Taler, meaning it's harder to know you did not just create a signing
oracle.

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