Subject: Re: [TLS] HTTPS client-certificate-authentication in browsers

From: "t.petch" <[email-masked]>
Date: Mon, 1 Aug 2011 21:30:14 +0200

---- Original Message -----
From: "Peter Gutmann" <[email-masked]>
To: <[email-masked]>
Cc: <[email-masked]>
Sent: Thursday, July 28, 2011 8:11 AM
Subject: Re: [TLS] HTTPS client-certificate-authentication in browsers

> Martin Rex <[email-masked]> writes:
> >Anders Rundgren wrote:
> >> Lots of banks wants to use CCA for their users.
> >
> >That is a non sequitur.
> >
> >Banks (here in Germany) have abandoned tradtional TANs based on the
> >unconditional presumption that client PCs are infested with malware, and
> >most banks in Germany are currently replacing indexed TANs (iTAN) presumably
> >based on the perception that malware on clients (trojans/phishing) has caught
> >up with iTAN procedure complexity.
> >
> >At this point, with the presumption that all client PCs are thoroughly
> >infested with malware, going for a Single Sign-On mechanism would be
> >completely braindead and irresponsible.
>
> That was my feeling as well.  Moving from TANs (or plain passwords if you're a
> US bank) to client certs is at best pointless and at worst a step backwards in
> security.  Even if you could overcome the monumental usability problems (and
> there's no evidence that we can do this), you end up with a mechanism that's
> even less secure than basic TANs because use of a TAN requires human
> intervention while a MITB (man-in-the-browser) can use your private key to
> sign whatever they want as often as they want without your knowledge.  Client-
> side PKI was designed for an attack model invented by cryptographers to
> justify the use of fun crypto stuff, but it has little (if anything) to do
> with the threats that we're actually facing today.
>

Coincidentally, one of the five big UK banks has today, 1st August, announced
HSBC Secure Key, a hand held card device that turns your PIN into a one-time six
digit passcode.  No technical details, but the advertisement claims that is is
an improvement on the German WWII devices (and half the advertisement is
encrypted - HX01896a1 54f30cd38 ...).  Another of the banks, Barclays, has had
PINsentry for a while, which takes your PIN and your debit card to generate a 8
digit passcode.

I have yet to use either but have seen technology similar to the former used
extensively in an Enterprise setting, for use by travelling salesmen in hotels
etc.

Tom Petch

> Peter.
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---

From: Peter Gutmann <[email-masked]>
Date: Tue, 02 Aug 2011 16:58:13 +1200

"t.petch" <[email-masked]> writes:

>HSBC Secure Key, a hand held card device that turns your PIN into a one-time
>six digit passcode.  No technical details,

It's just a SecurID variant, so no better than the static TANs that the German
banks are abandoning.

>Another of the banks, Barclays, has had PINsentry for a while, which takes
>your PIN and your debit card to generate a 8 digit passcode.

The Barclays device is a Gemalto CAP reader rebranded.  I don't know how
Barclays are using it (<cynic>given the security record of UK banks it'll be
"incorrectly"</cynic>), but if used correctly it's actually phishing-
resistant, you enter the transaction details and it generates a crypto MAC
from them which prevents a MITB attack.

Of course as certain folks from Cambridge have pointed out, you then have to
implement the underlying protocols correctly in order for the whole thing to
be secure, but it's good enough to stop phishers/MITB.

Peter.