phc-discussions - Re: [PHC] PolyPassHash is broken

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Message-ID: <541723CF.307@ciphershed.org>
Date: Mon, 15 Sep 2014 13:37:19 -0400
From: Bill Cox <waywardgeek@...hershed.org>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] PolyPassHash is broken

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On 09/15/2014 12:48 PM, Tony Arcieri wrote:
> On Mon, Sep 15, 2014 at 9:46 AM, Bill Cox
> <waywardgeek@...hershed.org> wrote:
> 
>> Would something like that work?
>> 
> 
> Unattended boot is pretty essential for any mission critical
> system, so probably not.
> 
> There are other ways to solve this problem though, like a hardware
> device that is only accessible at the time a computer boots.
> 

I agree that there are alternatives that do provide increased password
database security while allowing unattended boot.

Another thought would be to do the same for users as admins: until the
secret is derived, force users to answer a security question they set
up before, or send them a PIN on their phone as a second factor.  This
would only inconvenience users until the secret key is derived.

In any case, I have to agree with Steve that leaking parts of the
password hashes is a security risk.  I liked the security of
PolyPassHash up to that point, though it certainly would have
restricted use-cases if multiple admins were required to boot the
system and get the server back online.  I'm just wondering if
PolyPassHash could be use to enable more convenient login most of the
time, while providing at least the security level of having users
answer security questions all of the time.

This really isn't my area... I suspect Alexander would have more
insight into what is acceptable for most authentication servers.  This
is partly why I skipped reviewing PolyPassHash.

Bill
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