[Sls-sea-dls] Key Verification using CRC

[Biggerstaff, Craig (JSC-CD221)[LOCKHEED MARTIN CORP]]

I think it depends on the threat against which key verification is intended to protect.  If the threat is intentional tampering (however that might be carried out), then CRC verification is insufficient; an attacker easily could create a substitute key with CRC matching the original, if he knew it was necessary to match it.  But if the threat is merely a failure in onboard key storage, then CRC verification should still provide reasonably high confidence that the key onboard is the same as what was sent.  The OTAR directive already protects keys during transmission from the ground.


Craig

From: sls-sea-dls-bounces at mailman.ccsds.org [mailto:sls-sea-dls-bounces at mailman.ccsds.org] On Behalf Of Daniel.Fischer at esa.int
Sent: Sunday, April 17, 2016 6:13 AM
To: sls-sea-dls at mailman.ccsds.org
Subject: [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
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Tel: +49 (0) 6151 90 2718 - Fax: +49 (0) 6151 90 2718
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