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

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Date: Thu, 25 Jun 2015 03:20:46 +0100
From: Peter Maxwell <peter@...icient.co.uk>
To: "discussions@...sword-hashing.net" <discussions@...sword-hashing.net>
Subject: Re: [PHC] Why protect against side channel attacks

On 25 June 2015 at 02:18, Bill Cox <waywardgeek@...il.com> wrote:

> On Wed, Jun 24, 2015 at 5:55 PM, Marsh Ray <maray@...rosoft.com> wrote:
>
>>  Again, these cache timing side channels tend to leak the salts too.
>>
>
> How?  In most cases, salt never leaves the authentication servers and
> associated storage.  The salt is hashed/shredded before unpredictable
> addressing begins.
>

So the timing-attack recovers the hash of the salt just before the
data-dependent path.  That's, theoretically, reduced the difficulty of the
problem back to the constant-time portion of the PDF.  (it's not
particularly practicable and quite a remote possibility but many of the
topics discussed on this list have been of a similar nature)

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