phc-discussions - Re: [PHC] winner selection

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Date: Mon, 13 Apr 2015 21:19:59 +0000
From: Gregory Maxwell <gmaxwell@...il.com>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] winner selection

On Mon, Apr 13, 2015 at 9:17 PM, Thomas Pornin <pornin@...et.org> wrote:
> On Mon, Apr 13, 2015 at 03:35:42PM +0000, Gregory Maxwell wrote:
>> If I'd offered a Makwa competitor it would have had information
>> theoretic security for delegation (in exchange for making some
>> tricks/performance worse).
>
> Actually you can. The _definition_ of Makwa is not tied to a specific
> delegation mechanism.
>
> Last December, we were discussing these issues in this list with Adam
> Back, and he pointed out a method which offered information theoretic
> security for delegation. The method described in the Makwa specification
> (and implemented in the reference code) is not information-theoretic
> secure, but it is also about 12 times faster, which is why I chose it.
>
> However, the beauty of the thing, and the important point here, is that
> _both_ methods can be applied to Makwa as it is defined; it is merely an
> implementation issue. The function itself, and already computed hashes,
> are not impacted in any way by the delegation method you choose.
>
> (I should make an update to the reference code and specification to
> include that alternate delegation method. I'll see if I can free up
> some time for that job next week-end.)

Then I retract! I'd missed that.