phc-discussions - RE: [PHC] Testing Password Hashing functions

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Message-ID: <218AE73F98E99C4C98AF7D5166AA798E09077B07@TK5EX14MBXC287.redmond.corp.microsoft.com>
Date: Fri, 5 Apr 2013 16:54:22 +0000
From: Marsh Ray <maray@...rosoft.com>
To: "discussions@...sword-hashing.net" <discussions@...sword-hashing.net>
Subject: RE: [PHC] Testing Password Hashing functions

> -----Original Message-----
> From: Yann Droneaud [mailto:ydroneaud@...eya.com]
> Sent: Friday, April 5, 2013 8:53 AM
> To: discussions@...sword-hashing.net
> Subject: Re: [PHC] Testing Password Hashing functions
> 
> So using the PRNG test is probably a first evaluation step, but doesn't seems
> to be enough.

Agree. They're a useful sanity check.

RC4 is an example of a PRNG that wouldn't pass basic statistical tests.

https://en.wikipedia.org/wiki/Block_cipher_modes_of_operation#Counter_.28CTR.29
AES-128 in CTR mode with the key and plaintext inputs switched is a simple example of a PRNG which would pass all statistical tests and yet be completely broken.

An additional requirement of a password hashing function over a PRNG is that it require a significant amount of work to compute which no one can optimize away. I'm not sure statistical tests can help much here.

> So what others tools, methods are going to be used to evaluate password
> hash functions ?

My impression is that the construction of any potentially-reusable parts of the tools is so much easier than the analysis itself that it's almost a rite of passage for researchers to write their own. Unfortunately, only a few end up as open source.

There's a few at http://www.ecrypt.eu.org/tools/

Marc Stevens makes his MD5 and SHA-1 tools open source https://code.google.com/p/hashclash/

- Marsh