phc-discussions - Re: [PHC] A review per day

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Message-ID: <540C4216.1070009@ciphershed.org>
Date: Sun, 07 Sep 2014 07:31:34 -0400
From: Bill Cox <waywardgeek@...hershed.org>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] A review per day - skipping Makwa

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On 09/05/2014 04:10 PM, Bill Cox wrote:
> - Page 18, step 2, is that really x^2?  It makes sense to me if
> it's just x.

I reread it, and duh... It makes sense now.  The hash ix x^(2^(w+1)),
not x^(w^2).  I'm sure this is simply to protect the password derived
key x in case someone solves the knapsack problem

What happens in the future if Makwa is broken?  Application of a pre
or post cryptographic hash function would provide some protection,
though not much.

Having a pre-hash enables longer passwords, and provides some
protection in case Makwa is broken.  A post hash provides shorter hash
tags, but defeats work-increase.  Catena style garlic can still be
used for off-line increase, but when using delegation, it
unfortunately requires delegation for each level of work increase to
authenticate a user.  However, a new hash tag at a new work factor
could be recorded the first time a user logs in, so that's not too bad.

I think I prefer the Catena-style work increase, and work factor w
values that are powers of 2 only.  This enables short hash tags which
I think will be more popular.

Bill
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