Encryption control of SNDU

[Tarif.Zein-Alabedeen@space.alcatel.fr]

Hi every body

The current ULE draft does not address the issue of SNDU encryption which
we think is important.
In fact, a requirement has been identified in IP/MPE/MPEG to allow, when
necessary, data encryption at MPE level. Some IP/MPE/MPEG products already
implement this capability (e.g. Alcatel 9780)
Encryption is controlled using the 'payload scrambling control' field (2
bits) in the MPE header.

Consequently, it would be necessary to provision an "encryption-control"
field (2 bits) in the SNDU header.
This could also facilitate the transition from MPE to ULE
Here is a proposal for its definition :
   bit 1 : indicates if the SNDU is encrypted or not
   bit 2 : indicating the type of encryption (when active) odd/even (to
   allow key shift on the fly)

Adding 2 bits would require to add a complete byte to the SNDU header in
order that the header still an integer number of bytes. If this is not
acceptable from a performance point of view, we can envisage to shorten the
'length' field from 15 bits down to 13 bits (note that in MPE, the length
field is 12 bits).

waiting for your feedback
regards

T. Zein

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