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Date: Mon, 23 Jul 2012 12:55:13 +0200
From: Frank Dittrich <>
Subject: Re: mscash2 / hmac-md5 ambiguity

On 07/23/2012 12:46 PM, magnum wrote:
> On 2012-07-23 11:47, Alexander Cherepanov wrote:
>> mscash2 hashes in their canonical form are nevertheless accepted as
>> hmac-md5:
>> $ cat mscash2.john
>> chatelain:$DCC2$10240#chatelain#e4e15fdfafc8e715da9edec3611bfbff
>> $ john mscash2.john
>> Warning: detected hash type "mscash2", but the string is also recognized
>> as "hmac-md5"
>> Use the "--format=hmac-md5" option to force loading these as that type
>> instead
>> Loaded 1 password hash (M$ Cache Hash 2 (DCC2) PBKDF2-HMAC-SHA-1
>> [128/128 SSE2 intrinsics 8x])
>> guesses: 0  time: 0:00:00:02 0.00% (2)  c/s: 339  trying: 123456 - abc123
>> Session aborted
>> $ john --format=hmac-md5 mscash2.john
>> Loaded 1 password hash (HMAC MD5 [128/128 SSE2 intrinsics 12x])
>> guesses: 0  time: 0:00:00:02 0.00% (3)  c/s: 1120K  trying: 123man - 123mah
>> Session aborted
>> IMHO that's not very good.
> It was much worse until we forced hmac-md5 to lower precedence than
> mscash. Now it is just cosmetic. That hash *is* a valid hmac-md5 hash,
> with a salt of "$DCC2$10240#chatelain". We can stop this by
> black-listing certain format salts. That's OK with me but in some way
> it's a flawed path.

hmac-md5 doesn't have the "split() method unifies case" flag set, but
mscash2 has.
could we change that in a way that one format uses uppercase, the other
lowercase? Or would breaking backwards compatibility hurt too much?
If hmac-md5 is less likely to be cracked with john, we could convert
that one to upper case hex, and drop the flag from mscash2.


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