[Sls-sea-dls] Key Verification using CRC & OTAR Issue

Wed Apr 20 06:39:44 UTC 2016

Dear all,

In order to adopt the key verification that contains a computation of the 
CRC over the Key ID and the key instead of just the key, there is no 
change necessary in the PDU. Thus, I would almost make this an 
implementation specific thing. Some implementers may prefer to compute the 
CRC just over the key, others may want to compute it over the Key ID and 
the Key. We could cover this choice with a note. Regarding the latest mail 
from Craig, would the concerns not also be valid if only the key is used 
for the generation of the CRC?

I am not really in favour in formalising a "meta key" as well.  In my 
opinion, the way how the key, key ID, and CRC are generated and stored is 
not something the blue book should address. 

I have another problem that I want to share with you :):
In Cleveland, we have agreed that with OTAR the MAC is only computed over 
the set of [Key Id, Encrypted Key] blocks. This is fine. However, I now 
have problems with the baseline mode of the key encryption. If I choose 
AES-CTR (the recommended one as per algorithm BB) we need to transmit an 
IV for every key. I don't think that this is what we want, is it? 
Especially not for random data like a key. Any suggestions? The BB allows 
other modes if carefully considered. However, modes like CBC also require 
an IV. I am a bit reluctant to go for something as dangerous as ECB 
although it should not be a problem for keys.

Cheers,
Daniel

Dr. Daniel Fischer
----------------------------
Data Systems Manager
Ground Segment Engineering Support Office (OPS-GE)
Ground Systems Engineering Department
Directorate of Operations

European Space Agency - ESOC
Robert-Bosch-Str. 5
D-64293 Darmstadt - Germany
Tel: +49 (0) 6151 90 2718 - Fax: +49 (0) 6151 90 2718
Web: http://www.esa.int

From:   "Biggerstaff, Craig (JSC-CD221)[LOCKHEED MARTIN CORP]" 
<craig.biggerstaff at nasa.gov>
To:     "Moury Gilles" <Gilles.Moury at cnes.fr>, "Weiss, Howard" 
<Howard.Weiss at parsons.com>, "Saba Bruno" <Bruno.Saba at cnes.fr>, 
"Daniel.Fischer at esa.int" <Daniel.Fischer at esa.int>, 
"sls-sea-dls at mailman.ccsds.org" <sls-sea-dls at mailman.ccsds.org>
Date:   19/04/2016 15:49
Subject:        RE: [Sls-sea-dls] Key Verification using CRC
Sent by:        sls-sea-dls-bounces at mailman.ccsds.org

Bruno?s proposal is a good technical solution by itself, but I have 
concerns about introducing additional requirements into ground crypto 
systems for generation and storage of meta-keys.

The CRC may not itself be a critical security parameter in the FIPS 140 
sense (I think it is not, but I defer to others? judgment in this), but 
generation of the CRC requires access to critical security parameters, 
both the Key ID and the actual key itself.  So CRC generation would have 
to be performed within a validated crypto system, even if it were 
permissible to transmit and store the CRC outside the crypto system.

If Bruno?s proposal were adopted as-is, it appears unlikely to me that any 
generic, commercially-available crypto systems could satisfy the 
requirement.  For flight systems, this may not be an issue since flight 
implementations tend to be custom by their very nature.  On the other 
hand, ground systems that otherwise might be able to integrate 
commercially-available crypto systems would be forced into procuring 
custom implementations requiring e.g. FIPS 140 validation along with its 
additional time and expense.

Craig

From: sls-sea-dls-bounces at mailman.ccsds.org [
mailto:sls-sea-dls-bounces at mailman.ccsds.org] On Behalf Of Moury Gilles
Sent: Tuesday, April 19, 2016 3:46 AM
To: Weiss, Howard <Howard.Weiss at parsons.com>; Saba Bruno 
<Bruno.Saba at cnes.fr>; Daniel.Fischer at esa.int; 
sls-sea-dls at mailman.ccsds.org
Subject: RE: [Sls-sea-dls] Key Verification using CRC

Shall we adopt Bruno?s proposal ? In that case, we probably do not need 
the challenge-response transaction.

Gilles

Gilles MOURY 
CNES Toulouse 
De : sls-sea-dls-bounces at mailman.ccsds.org [
mailto:sls-sea-dls-bounces at mailman.ccsds.org] De la part de Weiss, Howard
Envoyé : lundi 18 avril 2016 19:27
À : Saba Bruno; Daniel.Fischer at esa.int; sls-sea-dls at mailman.ccsds.org
Objet : RE: [Sls-sea-dls] Key Verification using CRC

I agree with Bruno.

Howie

Howard Weiss
Technical Director

PARSONS
7110 Samuel Morse Drive
Columbia, MD 21046
443-430-8089 (office)
410-262-1479 (cell)
443-430-8238 (fax)
howard.weiss at parsons.com
www.parsons.com

Please consider the environment before printing this message

From: sls-sea-dls-bounces at mailman.ccsds.org 
[sls-sea-dls-bounces at mailman.ccsds.org] on behalf of Saba Bruno 
[Bruno.Saba at cnes.fr]
Sent: Monday, April 18, 2016 9:48 AM
To: Daniel.Fischer at esa.int; sls-sea-dls at mailman.ccsds.org
Subject: RE: [Sls-sea-dls] Key Verification using CRC
Dear all,

One solution to avoid the use of a challenge-response system and stay with 
the simple CRC for on-board key checking is to compute the CRC on BOTH the 
Key-ID and the key itself.

Ideally, what we know as a ?key? would be a ?Meta-Key?, comprising :

-          The Key ID, unique identifier of the key for the whole mission 
duration,
-          The Key itself (secret random data)
-          The CRC, computed on the Key ID and the key itself.

This ?Meta-Key? should be considered as an single entity, not splittable, 
being stored, transferred and distributed as is (on-board AND at ground 
level, from generation to destruction).

Cheers,

Bruno Saba 
CNES 
DCT/TV/IN 
18 Avenue Edouard Belin 
31401 TOULOUSE Cedex 9 
Tel : + 33 (0) 5 61 28 28 76 
Fax : + 33 (0) 5 61 28 19 96 

De : sls-sea-dls-bounces at mailman.ccsds.org [
mailto:sls-sea-dls-bounces at mailman.ccsds.org] De la part de 
Daniel.Fischer at esa.int
Envoyé : dimanche 17 avril 2016 13:13
À : sls-sea-dls at mailman.ccsds.org
Objet : [Sls-sea-dls] Key Verification using CRC

Dear all, 

I was discussing our new approach to key verification using the 
onboard-stored CRCs with David, 

He came up with a keen observation.   

The CRC-based key verification is somewhat weaker than one based on a 
challenge-response. The reason is that the CRC ensues you that the key at 
a certain slot is still OK in terms of integrity. In contrast to the 
challenge-response approach it DOES NOT tell you that the key is the same 
as the key with same key ID on ground. 

Is this an issue for us? What do you think? The only way we have to check 
key synchronisation is to use a key for actual traffic protection and see 
if it works. 

What do you think? 

Cheers 
Daniel 

Dr. Daniel Fischer
----------------------------
Data Systems Manager
Ground Segment Engineering Support Office (OPS-GE)
Ground Systems Engineering Department
Directorate of Operations

European Space Agency - ESOC
Robert-Bosch-Str. 5
D-64293 Darmstadt - Germany
Tel: +49 (0) 6151 90 2718 - Fax: +49 (0) 6151 90 2718
Web: http://www.esa.int[esa.int]
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