Date: Thu, 04 Sep 2014 10:00:35 -0400
From: Bill Cox <waywardgeek@...hershed.org>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] [SPAM?] Re: [PHC] A review per day - MCS_PHS

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Great.  Thanks!

I have only one remaining request for a code change.  In mcssha8.h,
you have:

// Total MCSSHA8 hash calculation
HashReturn Hash(DataLength hashbitlen,
	        const BitSequence *data,
		DataLength databitlen,
		BitSequence *hashval);

Could you change this to:

// Total MCSSHA8 hash calculation
HashReturn Hash(BitSequence *hashval,
                DataLength hashbitlen,
		const BitSequence *data,
		DataLength databitlen);

If I understand these parameters correctly, then this would match the
order in the PHS function.  I'm not saying that this is the only good
order, but I'm pretty sure that your current order will confuse people.

Bill

On 09/04/2014 09:36 AM, Mikhail Maslennikov wrote:
> I prepare new version of MCS_PHS - ver.3.  I put it on 
> http://crypto.systema.ru/PHC/MCS_PHS_v3.zip 
> <http://crypto.systema.ru/PHC/MCS_PHS_v2.zip> In it, I tried to
> consider all your notes Best regards Mikhail Maslennikov 
> 04.09.2014, 14:20, "Bill Cox" <waywardgeek@...hershed.org>:
>> 
>> 
>> 
>> On 09/04/2014 02:33 AM, Mikhail Maslennikov wrote:
>> 
>> Sorry, may be you analize old version MCS_PHS? New version
>> (ver.2) was upgraded 30.08.2014, as wrote JP. In ver.2 I remove
>> do ... while cycle. If you have problems to find latest version,
>> you can download it from
>> http://crypto.systema.ru/PHC/MCS_PHS_v2.zip.
>> 
>> You're right!  I reviewed the old code.  Sorry.  The new code
>> does is indeed a lot easier to read.  Line 72 doesn't make it
>> harder to read, but I think it is more common to just let the for
>> loop execute 0 times, so 72 could be deleted.
>> 
>> More importantly, if you could change the order of your variable 
>> parameters in the Hash function, it will make life easier for
>> users and reviewers.  That random variable order is what made me
>> think you must be a mathematician (that plus the fact that you
>> are a hashing function enthusiast).  They never seem to agree on
>> variable order.  We can't even get them to use HMAC with the
>> password and salt in a consistent order!  That is a real pain.
>> Every time I review code that calls HMAC, I have to go check
>> which variable order they used in the definition.
>> 
>> About reducing hash degree from 64 to outlen.  I want to use one 
>> specific feature of MCSSHA8 hash function: if Hi(M) and Hj(M) - 
>> hash with length i and j for some fixed message M, so this
>> values will be different as random values for any not equal i and
>> j. One of possible attack on Password Hashing Scheme like PBKDF
>> could be Dictionary Attack, when attacker try to build dictionary
>> for transformation hash->Hash(hash). In "standart" PBKDF it's
>> enough to build dictionary only for one hash function H, but if
>> we use MCS_PHS it's neccessary to buid dictionary for each of
>> different Hi. About internal buffer clearning - agree with you.
>> Now I try to prepare ver.3 whith this clearning. About "some
>> oddities in the code" and "fearful of using it" - please, look
>> latest version. May be it will be not so "fearful". About
>> mathematician - it's true. Thank you. Mikhail Maslennikov
>> 04.09.2014, 01:18, "Bill Cox" <waywardgeek@...hershed.org
>> <mailto:waywardgeek@...hershed.org> 
>> <mailto:waywardgeek@...hershed.org
>> <mailto:waywardgeek@...hershed.org>>>:
>> 
>> I'd love to discuss more about the merits of how you are hashing,
>> but I wont.  This list has already had to put up with me learning
>> the basics of password hashing schemes.  They don't need to put
>> up with me learning about hashing functions.  Your new code is a
>> lot less scary, and with the variable order fixed, it would pass
>> my code review.
>> 
>> Thanks for the reply, and sorry about reviewing the old version.
>> 
>> Bill
>> 
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