Re: [Ace] Adoption of Low Latency Group Communication Security Work in ACE

[Rene Struik <[e-mail]>]

Hi Sandeep:

Fair enough, but with, e.g., ECDSA, computation of the ephemeral key 
R:=kG can be carried out independently of the remainder of the signature 
computation (where one computes e:=h(m), and calculates 
s:=(1/k)(e-r*d)(mod n) and subsequently outputs (r,s), where r is 
derived from R). So, if one wishes to, one can pre-compute many 
ephemeral key pairs (k, kG) and use those on demand {David Naccache, if 
I remember correctly, elaborated on these types of "labor division" in a 
1998 paper}. So, in the Philips high-granularity luminary, the one 
simply hashes the state (still only a few-bytes entry) and then combines 
e with r, d, k, to produce signature component s -- a simple linear 
equation with two modular multiplies as cost.

Let's make things better...

Rene

On 7/25/2016 5:34 PM, Kumar, Sandeep wrote:
>
> Because sometimes a lightswitch can have more than two states.
>
> http://images.philips.com/is/image/PhilipsConsumer/6916431PH-IMS-en_GB?wid=494&hei=435&$pnglarge$
>
> The color dial on this switch (src: 
> http://www.philips.co.uk/c-p/6916431PH/livingcolors-remote-control) 
> can set the color of lights one chooses. That would be quite some 
> precomputations.
>
> Sandeep
>
> -----Original Message-----
> From: Ace [mailto:[e-mail]] On Behalf Of Stephen Farrell
> Sent: Monday, July 25, 2016 9:26 PM
> To: Somaraju Abhinav; Michael StJohns; [e-mail]
> Subject: Re: [Ace] Adoption of Low Latency Group Communication 
> Security Work in ACE
>
> On 25/07/16 17:59, Somaraju Abhinav wrote:
>
> > we essentially have 50-100 ms for the signing+verification process and
>
> > I do not know of a solution that does this
>
> Just a clarifying question: why can't the signing possibly be done 
> asynchronously? E.g. the private key holder could sign a value that 
> will only be sent later - as long as it has one of those ready to emit 
> whenever needed one can ignore the signing time. That can have power 
> consumption consequences but I'd guess that's ok for a lightswitch.
>
> If signing can be done ahead of time, then only verification time has 
> to be considered.
>
> S.
>
>
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