[Security] Enhancements to H.233 and H.234

[Patrick Luthi]

Roni,

See my answers in-line!

Regards,

Patrick

At 16:03 9/12/2002 +0300, Even, Roni wrote:
>Patrick,
>I looked at the contributions and have some comments.
>
>1. In H.233 why the new tag class, why don't you use 11 as the rest of H.233
>messages.

We used 00 because it defines the universal tag class (11 being context
specific), and we thought that SE_NULL, as data type null message, would
best belong to that class. This makes it consistent with ASN.1.

>2. By adding the new encryption algorithm you need a longer DH prime. In
>H.235 they have a table in annex D which is based on RFC2412. Do you think
>we should have the option to recommend the same numbers as H.235 does.

H.233 nor H.234 are specifying any Diffie Hellman prime values and my
understanding is that it is left to the implementor to choose the best
value. I see your point, and in the interest of interoperability, a
specified value would help.
I will think about how to best integrate some text specifying prime values
in H.234. One idea was to add a note in the section about Diffie Hellman
(clause 4/H.234) saying something (inspired by D.7.1/H.235) like this:
It is recommended to use a prime value of 512 bits for the DES algorithm
(when exportable security is of concern), 1024 bits for Triple DES and AES
algorithms (when high security is of concern), and 1536 bits for Triple DES
and AES algorithms (when very high security is of concern).
Would that address your concerns? Any feedback or comments are welcomed!


>Regards
>Roni Even
>
> > -----Original Message-----
> > From: Patrick Luthi [mailto:patrick.luthi at TANDBERG.NO]
> > Sent: Friday, August 30, 2002 1:54 AM
> > To: ITU-SG16 at echo.jf.INTEL.COM
> > Subject: [Security] Enhancements to H.233 and H.234
> >
> >
> > Dear experts,
> >
> > We would like to share with you 2 proposals for enhancements
> > to H.233 and
> > H.234 that we are planning to submit to the October meeting of SG16.
> >
> > Enhancements to H.233: this contribution proposes to add the
> > Triple Data
> > Encryption Algorithm (TDEA or triple DES) and the Advanced Encryption
> > Standard (AES) to the list of algorithms in H.233 along with
> > corrections of
> > some inconsistencies.
> >
> > Enhancements to H.234: this contribution proposes changes to
> > H.234 to allow
> > the exchange of asymmetric length of encryption keys.
> >
> > Please let me know if you have any suggestions or comments!
> > The plan would
> > be to ask for Consent for both recommendations at the closing of the
> > upcoming SG16.
> >
> > Best regards,
> >
> > Patrick
> >
> > _____________________________
> > Patrick Luthi
> > Manager - Technical Standards
> > Rapporteur (chairman) for the ITU-T multimedia systems, terminals and
> > data-conferencing Experts group (Question 1/16)
> > TANDBERG
> > N-1366 Lysaker, Norway
> > Phone: + 47 67 125 125
> > e-mail: patrick.luthi at tandberg.no
> >

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