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Re: [Taler] Hello

From: Christian Grothoff
Subject: Re: [Taler] Hello
Date: Wed, 7 Dec 2016 08:18:46 +0100
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On 12/07/2016 12:13 AM, Joerg Baach wrote:
> Hi Christian, hi Jeff,
> thanks a lot for your explainations.
> With regards to the refresh - isn't the whole point of blind signatures
> that the _transactions_ can't be traced, e.g. that your can rely on the
> protocol that no information is leaked? Hiding the IP looks like a
> "second line of defense" to me, a bit like bitcoin. Or do I miss something?

You're missing that linking the refresh to the spending is not an issue,
running the refresh operation is just part of the overall spending
transaction, that does by itself not deanonymize you, as long as refresh
does not require you to disclose your identity. Hence exposing your IP
during refresh is the only issue, and for that Tor fixes it nicely.

> On the merchant's certificate - I understand that you want to use x509.
> But _who_ is signing in the end? The way I understand Christian's answer
> it would piggypack on the existing certificate infrastructure, avoiding
> to roll out a new one, but also inherit the trust issues, with way to
> many CAs of questionable trustworthyness. Why not only trust a small
> subset of CAs, or can the exchange define what CAs to trust?

Well, the customer already trusts exactly this infrastructure to
identify the merchant in the first place, and to confidentially
negotiate the contract.  And it's completely up to the browser to decide
which CAs to trust, not to the exchange. The exchange is not part of the
relationship between customer and merchant. Here, ultimately the
customer is in control and can decide whether to trust the X.509 PKI.

> Lastly, the NFC. A nice approach to use the merchant as a bridge to the
> issuer. I have to think about that one. I wonder though if in a person
> to person situation cash is much more reliable, and also faster and
> untraceable.

More reliable? I'm right now in India. Watch the news. Cash is hardly
reliable, and once you only have INR 2000 and INR 100 bills, counting
the change also takes quite some time (and having it in the first place
is a nightmare as well!!!).

So no, cash is not always the answer ;-)

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