[Cryptography] Show Crypto: prototype USB HSM

[Ron Garret]

On Apr 12, 2016, at 5:39 PM, Tony Arcieri <bascule at gmail.com> wrote:

> On Tue, Apr 12, 2016 at 8:28 AM, Ron Garret <ron at flownet.com> wrote:
> Some hardware tokens have an input device built in (usually a push button, sometimes a fingerprint sensor) which needs to be activated before the token will operate, but these are still subject to phishing attacks
> 
> Not to rain on your parade, but if you're talking about authentication contexts, U2F solves the phishability problem by deriving domain-separated keys per origin, so it's not possible for an attacker to leverage it for phishing purposes.

This HSM is much more general-purpose than a U2F token.  It could be used as a standalone bitcoin wallet a la Trezor.  It can be used to decrypt messages and display them on the built-in display so that even an adversary with root accesss to your laptop couldn’t read the cleartext.  The firmware doesn’t support this yet, but it’s a mere matter of programming :-)

But even U2F tokens can be phished for some value of “phished”.  It’s true that you can’t extract the keys, but if an attacker owns your machine and you have a U2F token installed, the attacker can log into any site you can log into.  Even if the token has a button you need to push to activate it, it’s probably not hard to fool most users into pushing the button to authorize an authentication for an attacker.

With a display, the token can say, “You are about to authorize…” and describe exactly what it is that it is being asked to do so that you know what you’re authorizing in a way that an attacker cannot control even with a completely compromised client.

rg

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