Re: [secdir] Secdir review of draft-herzog-static-ecdh-05

David McGrew <mcgrew@cisco.com> Fri, 11 March 2011 20:31 UTC

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From: David McGrew <mcgrew@cisco.com>
To: "Herzog, Jonathan - 0668 - MITLL" <jherzog@ll.mit.edu>
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Date: Fri, 11 Mar 2011 12:32:45 -0800
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Subject: Re: [secdir] Secdir review of draft-herzog-static-ecdh-05
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Hi Jonthan,

On Mar 10, 2011, at 12:41 PM, Herzog, Jonathan - 0668 - MITLL wrote:

>
> On Mar 10, 2011, at 1:12 PM, David McGrew wrote:
>>
>>
>>>
>>> However, SP800-56A does define cofactor ECDH. So let me propose the
>>> following citation scheme:
>>>
>>> * ECDH in general: RFC 6090
>>> * Standard ECDH: RFC 6090
>>> * Co-factor Diffie-Hellman: SP 800-56A, Section 5.7.1.2
>>> * Full public-key validation: SP800-56A, Section 5.6.2.5
>>> * Partial public-key validation: SP800-56A: Section 5.6.2.6
>>> * Key-derivation function... still working on it.
>>>
>>> Thoughts?
>>
>> That looks good to me.  Let me know if I can help with the KDF.
>
>
> I'd appreciate it, thanks. One of the goals of this draft is to  
> remain as compatible with RFC 5753 as possible, so as to impact  
> implementations as little as possible. RFC 5753, for its part,  
> specifies the KDF in SEC1. And the KDF in SEC1 is just the 'simple  
> hash function construct described in ANSI X9.63'. So, do you think I  
> can cite X9.63 as the normative reference? And if so, what are your  
> thoughts on citing SEC1 as an informative reference for this KDF?  
> SEC1 is, after all, freely available on the web.

Good point.

I hope that the KDF from X9.63 that is referenced in SEC1 is the  
Concatenation Key Derivation Function (Section 5.8.1 of SP800-56A), or  
if not, the ASN.1 Key Derivation Function (Section 5.8.2).   The  
800-56A text on key agreement schemes says that they are based on  
X9.63 algorithms, though it doesn't explicitly mention the KDFs.

David

>
> (Note: I'm still chasing down the ANSI spec to ensure that it does,  
> in fact, match the description in SEC1.)
>
> Thanks.
>
> -- 
> Jonathan Herzog							voice:  (781) 981-2356
> Technical Staff							fax:    (781) 981-7687
> Cyber Systems and Technology Group		email:  jherzog@ll.mit.edu
> MIT Lincoln Laboratory               			www:    http://www.ll.mit.edu/CST/
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