Subject: RC4-HMAC

From: Ken Raeburn <[email-masked]>
Date: Mon, 4 Dec 2000 17:12:05 -0500 (EST)

Doug put this on the agenda:

  RC4-HMAC as "standard" etype - John Brezak (Microsoft)
        John reports that there are at least 3 implementations of
        Kerberos which have this, so should it be standard? 

I didn't realize it, because it hadn't been announced here (AFAICT),
but there's a new draft (draft-brezak-win2k-krb-rc4-hmac-02.txt) that
came out in November, and it looks significantly different from the
-00 and -01 versions.

It incorporates key derivation "as defined in RFC1510bis" (or similar
language), and then goes on to describe a completely different
mechanism using an MD5 HMAC.  A different list of key usage numbers
that doesn't match up with all the uses in RFC1510bis is also given,
with no explanation for the changes; making one implementation handle
both will be a pain in the backside, though a sort of translation
table from RFC1510bis numbers to RC4 numbers might work.  There were
some other bits I had questions on (mostly the reasoning for certain
decisions), but I'd have to go back and check it again.  I did notice
the checksum number chosen for HMAC MD5 is still negative -- that is,
in the "local use" range.  If it's going to be an IETF standard, it
should have a positive number, IMNSHO.

My main question is:
  Which versions of this spec have been implemented (and by whom), and
  what version are we talking about making a standard?

Ken