Re: [Cfrg] I updated 3 drafts related to a FSU KeyEX

Stephen Farrell <stephen.farrell@cs.tcd.ie> Thu, 28 April 2016 10:06 UTC

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To: KATO Akihiro <kato.akihiro@po.ntts.co.jp>, Michael Scott <mike.scott@miracl.com>, "cfrg@irtf.org" <cfrg@irtf.org>
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From: Stephen Farrell <stephen.farrell@cs.tcd.ie>
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Subject: Re: [Cfrg] I updated 3 drafts related to a FSU KeyEX
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On 28/04/16 10:58, KATO Akihiro wrote:
> Hi Stephen,
> 
> At FSU case, the KGC cannot get session key.
> 
> Look the page 7 and 8 of
> https://www.ietf.org/proceedings/94/slides/slides-94-cfrg-0.pdf . The
> session key encrypted ephemeral public key. If the KGC have all static
> secret key, that cannot see session key and plain text.
> 
> There is no key escrow on FSU key exchange.

Eh? Doesn't slide 4 show that the KGC can fake anyone since
it generates their secret keys? That's close enough to mandatory
key escrow for me though sure, perhaps a better term for the
KGC rules-them-all would have been better:-)

S.

> 
> Regards.
> 
> On 2016/04/28 18:26, Stephen Farrell wrote:
>>
>> Hi Mike,
>>
>> On 28/04/16 09:35, Michael Scott wrote:
>>> Maybe the more accurate phrase "n uniquely attractive targets" where
>>> n=2,3,4... doesn't carry quite the same punch!
>>
>> I'm sorry, but for me, it does have exactly the same
>> punch. If there are key generators, they can collude
>> or be coerced. Or even more likely, in a realistic
>> commercial Internet-scale deployment, it's quite likely
>> all of them (even if operated by different entities)
>> may be running on one or two mega-hosting platform,
>> so there may well be only one thing to break into
>> even if it looks like N things.
>>
>>  From my POV, the mandatory key escrow aspect of IBE
>> is basically fatal for all but possibly some small
>> set of niche applications.
>>
>> Cheers,
>> S.
>>
>>
>>
>>
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> 
> 
>