[Sls-sea-dls] Fw: Question regarding the SDLS EP Standard

[Daniel.Fischer at esa.int]

Dear all,

Could ask you to take a look at the questions that David sent a while 
go...some of them need answers before a red book can be produced.
My take:
Q1 is a typo and will be corrected. --> No further discussion needed
Q2: This should be the case. What do the others think? Do we need to be 
explicit there?
Q3: This is a critical one and we don't have an answer at the moment. I 
remember we discussed this in the WG already but I am not sure we came to 
a conclusion. This needs to be clarified in the standard. Any opinions?

Cheers,
Daniel.

Dr. Daniel Fischer
Head of the Engineering Support Section, OPS-GES
Ground Systems Engineering Department
Directorate of Operations
ESA - ESOC
Robert-Bosch-Str. 5, D-64392 Darmstadt, Germany
Tel. +49 6151 90 2718 |  E-mail: Daniel.Fischer at esa.int
----- Forwarded by Daniel Fischer/esoc/ESA on 31/03/2017 08:51 -----

From:   David.Koisser at esa.int
To:     sls-sea-dls at mailman.ccsds.org
Cc:     "John P. Lucas" <John.P.Lucas at ivv.nasa.gov>
Date:   01/03/2017 11:04
Subject:        [Sls-sea-dls] Question regarding the SDLS EP Standard
Sent by:        "SLS-SEA-DLS" <sls-sea-dls-bounces at mailman.ccsds.org>



Dear SDLS WG members, 

John and I have completed setting up the interoperability testing 
environment and now we are doing a few finishing touches. Whilst doing 
this a few questions arose regarding the SDLS EP standard: 

1. In Section E4.2.2 (in the baseline mode description of Key Activation) 
and the following key procedures, it defines the Key ID fields to have a 
length of 16 bits. And then states: 
"Values 0-65535 shall not be used to reference session keys." 
Which would be all possible Key IDs and leave none for any session keys. 
Can you clarify? 

2. While we are fairly sure it is implied: Does the M&C procedure Set ARC 
set the IV instead of the SN parameter in the regarding cases (e.g. 
AES-GCM)? 

3. The standard is not addressing how to distinguish if a GVCID is 
regarding the TM or TC channels for the Start SA procedure. An example to 
clarify: 

A mission wants a different SA assigned on VC 0 for the uplink (e.g. 
authentication only) than the VC 0 for the downlink (e.g. authenticated 
encryption). To be able to set this with the Start SA procedure, it needs 
a way to distinguish between the TC and TM channel mapping to SPIs. As the 
GVCID is defined as: 
GVCID = TFVN + SCID + VCID 
And the 2 bits long TFVN may have the following values: 01 -> AOS; 10 -> 
Proximity-1; 00 -> TM- *or* TC-SDLP 
The GVCID alone is not enough to distinguish between TC and TM and we are 
currently using a custom data structure for unambiguously identifying the 
channels in the Start SA procedure. 

Best Regards, 
David Koisser
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