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Re: keyed-MD5 placement of secret
William Allen Simpson says:
> I asked the Security Area this many months ago. We discussed it on the
> M-Bone wrt IPv6, and I believe it was discussed in other fora. Here is
> the decision:
> > Date: Sun, 11 Sep 94 11:34:19 -0400
> > From: Jeffrey I. Schiller <jis@mit.edu>
> > .... I would recommend the front of
> > the data. in that fashion you can precompute the internal MD5 state (i.e.,
> > initialize MD5, feed it the key and then snapshot its internal state)
> > in order to get better performance.
> >
> Now, unless the Security Area reverses itself, and changes the standard
> in SNMP also, that is what we will use in the AH implementations going
> forward as we speak. There is absolutely no reason to do it differently
> for each MD5 usage.
This is faster but less secure. It isn't possible to tel exactly how much
less [to the best of my knowledge]. Some attacks are possible, unless
length is in certain place and such... I'd ask - what's the rush?
I personally won't care about speed advantage of precomputed
MD5 (unless I'm cracking MD5 key, of course :-)...
--
Regards,
Uri uri@watson.ibm.com N2RIU
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