[CESG] CCSDS 355.0-R-1, Space Data Link Security Protocol (Red Book, Issue 1) vs Proximity-1

[Gian.Paolo.Calzolari at esa.int]

Dear All,
        as you know is these days CESG Poll CESG-P-2011-03-005 is ongoing 
for the Approval to release CCSDS 355.0-R-1, Space Data Link Security 
Protocol (Red Book, Issue 1) for CCSDS Agency review.
Peter has approved the poll (thanks!) with some remarks.
I think it is worth to address his first remark (i.e. Why is Porx-1 not 
addressed along with TM, TC & AOS?  Is there the assumption that if data 
is securely delivered to space that relaying it is then not a problem? ) 
for sake of clarity.

The shortest answer to the question is that Proximity-1 is not addressed 
on purpose as SDLS WG decision; i.e. SDLS protocol is meant to protect TC 
Direct From Earth (DFE) and TM Direct To Earth (DTE)  space links. 

Here are some points providing the rationale:
- The prime threats we are aiming to protect from with this SDLS protocol 
are on earth, not in space and surely not in deep space. This is why SDLS 
WG did not consider compatibility with Proximity-1 a necessary feature of 
the SDLS protocol. The User Requirements Document (URD) which was the 
basis for SDLS development did not list Proximity-1 as target data link 
protocol for the above mentioned reason. 
- The WG had originally gone into the SDLS protocol development with the 
intent of creating a ?shim? to allow it to work with TM, TC, AOS, *and* 
Prox-1.  But the more they looked at Prox-1, the more they realized that 
it would require changes to Proximity-1 to allow SDLS to work (they 
consulted with Greg Kazz on this).  So, WG idea was to define the SDLS 
protocol for those CCSDS link layer protocols that would not require any 
changes and then influence the next rewrite of Proximity to allow SDLS to 
be seamlessly incorporated. 
- I think also  that there would be a  big number of issues (for key 
management etc.) to be tackled and recommending CCSDS 355.0-R-1 for 
Proximity-1 would just be misleading.without a thorough analysis of multi 
hop (even if limited to one hop right now) encrypted environment. 
- In conclusion, adding Proximity-1 to SDLS would require serious rework 
(unless one is looking for mere formatting inclusion) and when its 
revised, the WG will include it in SDLS.

I hope this is clarifying the issue.

Best regards

Gian Paolo

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