Re: arcfour: hmac-md5 vs. md5

[Elrond]

Any news on this?

Or are you just plain busy? :)


    Elrond


On Fri, Apr 28, 2006 at 05:46:25PM +0200, Elrond wrote:
> 
> Okay,
> 
> this is still about TGS. I just noticed, that we have too
> many buttons (parameters) to press and try stuff. So I
> decided to start from scratch and look only at one
> parameter:
> 
> arcfour-hmacs default checksum.
> Either hmac-md5 or plain-md5 (MD_RSA_MD5).
> (I modified crypto-rc4.c for this "parameter change").
> 
> 
> Other parameters:
>       cipher: "arcfour-hmac" only.
>       preauth: enabled
>       subkey in TGS: enabled
> 
> 
> w2k3-kdc:
> 
>       Sending a TGS with hmac-md5 gets me a "Message
>       stream modified" from the w2k3-kdc.
> 
>       Doing the same with plain-md5 gets me a response,
>       that shishi can't decrypt.
> 
> heimdal-kdc:
>       Version: 0.7.2 from Debian/testing
> 
>       Both variants work and I can't really discover any
>       difference.
> 
>       Both give this warning from shishi at TGS-time:
> 
>       "libshishi: warning: KDC bug: Reply encrypted using wrong key."
> 
> 
> >From my limited point of view, this looks like shishi and
> heimdal are consistent to each other with the hmac-md5, but
> shishi and w2k3 do not seem to share this.
> 
> This is particular confusing to me, as arcfour-hmac was
> invented by the guys at ms. So either their spec isn't
> correct or heimdal and you seem to have misread it (no
> reproach intended!).
> 
> So what next?
> 
> 
>     Elrond
> 
> 
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