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Re: 3DES with 40-bit key?

jim@mentat.com wrote:
> 
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> Ari Huttunen wrote:
> 
> > Many of you will think this issue is braindead.
> > I agree. However, as I understand that from now
> > on the only MUST IMPLEMENT algorithm for ISAKMP
> > and IPSEC is 3DES, the issue of what to do with
> > export control rises. So, assume that export
> > control limits the key length to 40 bits. How
> > would I specify and negotiate this with IKE?
> 
> I wouldn't say it's a braindead idea -- just that it's wrong.  3DES is
> defined in RFC 2451 as having a 192-bit key; 168 bits participate in
> the key schedule.  The key length is not negotiable for this cipher.
> If you were to do the equivalent of the CDMF transform to create a
> DES-like cipher with 40 bits of strength, it wouldn't be DES;
> similarly, a 40-bit version of 3DES would not be 3DES, and you would
> not have implemented this cipher, so you would not have satisfied any
> MUST IMPLEMENT clause.

So, which algorithm would you recommend for an export hampered
IPSec box to implement? Remember that it will have to be interoperable
with the other routers out there, which by now will only have to support
3DES. (This was agreed to at last IETF, no RFCs have been changed yet.)
Of course this is subject to security policy decisions.

BTW, I find it hard to imagine someone implementing 3DES but not
implementing
DES. This too, however, is slightly beside the point.

> 
> If you did something like this and tried to pass it off as a conforming
> IPSec implementation, it would be fraudulent.  If you can't get export
> licenses for the algorithms you want, then you can't export them.
> Simple as that.
> 
> By the way, the "weak ciphers for US export" limit has been raised to
> 56 bits with a BXA review.

I wonder... If I remember correctly what the Wassenaar agreement
stated, 56 bits was allowed for some uses, while still not allowed
for all possible uses. In any case, for this discussion it can
be any number of bits less than what 3DES needs.

> 
>         Jim Gillogly

Ari Huttunen
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