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Date: Thu, 21 Mar 2013 16:42:17 -0500 (CDT)
From: Steve Thomas <>
Subject: RE: [PHC] Password Hashing done wrong on CISCO IOS

> On March 21, 2013 at 4:11 PM Marsh Ray <> wrote:
> > -----Original Message-----
> > From: Per Thorsheim []
> > Sent: Thursday, March 21, 2013 11:14 AM
> > To:
> > Subject: Re: [PHC] Password Hashing done wrong on CISCO IOS
> >
> > Well, at least I guess Jens should be able to share his side of this, but
> > honestly I don't think that's the interesting part. This has to be a serious
> > implementation error by somebody who doesn't know crypto well enough,
> Implementation errors happen to *everyone*, even folks who know tons about
> crypto. In practice, it seems that some functions are more prone to subtle
> implementation errors than others.
> Say the developer accidentally left in some test code that ignored the round
> count and salt parameter and substituted the constant values of [nil] and 1, I
> agree we probably wouldn't learn much new from that. On the other hand, if the
> error came from C code making assumptions about the signedness of 'char' or
> sign extension of a shift right operator (e.g., Java) this might be
> interesting to hear about.
> > and (crypto) QA / testing before the affected versions of IOS got released
> > must have been weak, if at all present over the usual "if it reboots fine
> > all is
> > good" testing.
> The challenge with subtle password hash bugs is that QA can do a thorough job
> of black-box testing and still not catch 1 round instead of 1000. Customers in
> the field are even unlikely to notice or complain about it.
> Bugs like this get caught only by either comprehensive test vectors and/or 3rd
> party white-box testing.
> - Marsh

It gets caught when anyone does a quick look at a standard base64 encoded SHA256
vs Cisco type 4:
VmfGkLmm/FDPyMTthaWnH1LeNOzoo51UIfFtafyTOre  (Cisco type 4)
XohImNooBHFR0OVvjcYpJ3NgPQ1qq73WKhHvch0VQtg= (Standard base64)

Then there's the other 21 duplicate characters that are easily found with a
simple script which confirms it (1 in 2 ^ 18 [quick look] vs 1 in >2 ^ 84
[script]). Then just do a simple character substitution with a few hashes until
you either realize the base64 character set or you get all the characters.

This was more than likely already known years ago and kept secret.
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