phc-discussions - Re: [PHC] Why protect against side channel attacks

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Message-ID: <CAOLP8p70hvwvCodvSRMX8Ab05Uk0RZSYr-u3YKBoOtN+MM21rg@mail.gmail.com>
Date: Wed, 24 Jun 2015 17:32:32 -0700
From: Bill Cox <waywardgeek@...il.com>
To: "discussions@...sword-hashing.net" <discussions@...sword-hashing.net>
Subject: Re: [PHC] Why protect against side channel attacks

On Wed, Jun 24, 2015 at 5:18 PM, Greg Zaverucha <gregz@...rosoft.com> wrote:

> Yes I (and others, like you Krisztián) have understood the technical
> mechanics of how the attack would work for a while.  But I hadn't thought
> through the whole scenario that I described in my email, and the part that
> was new to me was that there isn't a good way to recover from this type of
> attack...
>

To recover from a cache-timing attack where the attacker has the salt and
usernames, you can simply require users to reset passwords, just like we do
normally.  This gives you a new password/salt database, which should be
better protected in the future.

I am confused why a company would more easily learn of a password database
leak than a cache timing attack combined with leaking the salt database.
The usual signal a company notices first is a ton of complaints from users
with PWNed accounts.

Bill

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