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Re: Crypto agility in SCRAM + draft-josefsson-password-auth?
On Mon, Mar 17, 2008 at 05:48:14PM -0700, Chris Newman wrote:
> I am not convinced the security value of PBKDF-2 offsets the additional
> complexity it adds. Remember there is negative security benefit if we use
> PBKDF-2 and the additional complexity pushes the mechanism over the edge
> into the "not worth implementing" category. It may be not a lot of
> complexity, but every bit matters.
It adds very little additional complexity. Give it a second read...
> While I would personally be fine with abandoning MD5 in favor of SHA1 given
> my code toolkit has both algorithms, I'm concerned about the impact.
Consider the possibility of widespread deployment. Then will come the
FIPS certification requests, then we'll hate MD5.
> Everyone's code toolkit includes MD5, but use of SHA1 is quite rare in
I don't believe that people don't have SHA-1. On Linux? On Solaris?
On Windows? On *BSD? And bindings to most populate languages? With
most or all of the top FOSS licesnses (GPL, BSD, MPL, ...)? I haven't
looked at all of them, but I'll eat a shoe (OK, maybe I won't eat a
shoe, but I'll buy a round of beers) if any major OS doesn't have it :)
I don't know enough about embedded devices, but I imagine J2ME, for
example, must have SHA-1 support by now.
Incidentally, for a mechanism like SCRAM deploying a new hash implies
re-enrolling all users (alternatively: the enrolment site keeps all
passwords in the clear; ugh). This is one reason why picking a good
hash now matters.
> applications at the moment. Switching away from MD5 will create a
> deployment barrier. Again, it doesn't matter how much more secure SHA1 is
> than MD5 if the SHA1-based mechanism doesn't deploy and an MD5-based one
> might have deployed. I'd like to hear from other SASL implementers before
> making a firm decision on this one: do you have SHA1 in your code toolkit?
> If not, how hard would it be to add it and would that be a deployment
> barrier?
I'd also like to hear about embedded environments...
Nico
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