[Sea-sec] Comment re: key sizes in Algorithm document

Mehmet Adalier madalier at antarateknik.com
Thu Jul 5 19:52:20 UTC 2018


This is my first posting. appreciate any comments.

I am part of a US based small R&D company, Antara Teknik LLC. We became a CCSDS industry associate late last year.

We do a fair amount of network-security based R&D and as of late we have been drafting/implementing a Cipher Suite for BPsec.


Symmetric key sizes of 256-bit and asymmetric key sizes of 4096-bit are substantially more secure than 128-bit and 2048-bit. 

For new systems ‘shall’ for these larger key sizes definitely is the right direction, to ensure higher security strength going forward.


However, 128-bit symmetric and 2048-bit asymmetric keys are still considered safe –at least in US. (see below chart based on published NIST SP).

Thus, my suggestion would be that for ‘existing systems that cannot be updated’ the shorter key lengths are ‘supported’ (i.e., ensure backwards compatibility), but for new systems the larger keys ‘shall’ be used. (with the implication that for new systems shorter keys may not be used)


Mehmet Adalier

Antara Teknik LLC



From: SEA-SEC <sea-sec-bounces at mailman.ccsds.org> on behalf of "Sheehe, Charles J. (GRC-LCN0)" <charles.j.sheehe at nasa.gov>
Date: Thursday, July 5, 2018 at 11:43 AM
To: "sea-sec at mailman.ccsds.org" <sea-sec at mailman.ccsds.org>
Subject: Re: [Sea-sec] Comment re: key sizes in Algorithm document




larger key size a "shall" but allow the smaller key sizes as "may" with a note strongly discouraging the smaller key sizes. 


I do not agree with allowing a "may".


The system will be a non-compliant system.

The system will lose secure interoperability with the large key systems and the loss of any presumed security over time and with the advent of Quantum computers in ~5 years.

It is understandable that older systems will age out of compliance with current security requirements.

It would be bad practice, if I do not strongly object and allow 128 bit key systems to be built knowing that its security will become markedly insecure during the lifetime of this document.



>From publically available document. 


These are my opinions and do not reflect the official position of NASA. 








Charles J. Sheehe III

Computer Engineer

Glenn Research Center

21000 Brookpark Rd

Cleveland, OH 44135

Charles.J.Sheehe at NASA.GOV

Office: 216-433-5179


“Omnia vero”



-----Original Message-----
From: SEA-SEC <sea-sec-bounces at mailman.ccsds.org> On Behalf Of Weiss, Howard
Sent: Thursday, July 5, 2018 1:37 PM
To: sea-sec at mailman.ccsds.org
Subject: [Sea-sec] Comment re: key sizes in Algorithm document


We currently have two documents in CESG polling for Agency Review.





On the Algorithms document, we have increased the minimum key sizes.  However we have a comment from Mario Merri (ESA):





"The main change is the strenghen of the authenticaltion keys. These have been increased, thus making implementations that followed the previous CCSDS recommentation not-compliant. Why has the document update not been made in a backward-compatible manner, still strongly recommending the new key lengths?"





Peter Shames suggested that we make the. This would satisfy Mario's backward compatibility issue.  





Any comments?  Any disagreements?  Any other suggestions?

























Howard Weiss, CISSP



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