Hi George,

Thanks for reading the paper!


Yes, the signatures we use in our scheme are completely unrelated to the normal 
operation of the log and only come into play in the event of log misbehavior. 
Ordinary log behavior can continue to use standard signatures.


The important property of the signatures we use in our scheme is the "proof of 
knowledge of a signature." The idea is to use this proof to show that we have 
committed values that actually correspond to objects on the log. We then use 
range proofs and other simpler zero knowledge proofs on commitments to show 
that they fulfill the relationships required to complete the proof.


thanks and let me know if you have any more questions,

~saba

________________________________
From: George Tankersley <[email protected]>
Sent: Monday, April 10, 2017 4:34:37 PM
To: Saba Eskandarian
Cc: Ben Laurie; [email protected]
Subject: Re: [Trans] Privacy-preserving proof of sct exclusion

Hey Saba,

Read this paper with interest. Thanks for sharing!

Am I correct that the range proof signatures are completely unrelated to normal 
log operation? That is, the ordinary log behavior continue to use commonly 
supported algorithms (RSA-PKCS1v15 or ECDSA) with only the intermediate range 
values being signed to admit proofs of signatures under commitment?

On Wed, Apr 5, 2017 at 12:27 PM, Saba Eskandarian 
<[email protected]<mailto:[email protected]>> wrote:
Since there wasn't time to present these privacy preserving proofs at the 
meeting last week, I thought it might be of interest to the list that I'll be 
presenting the idea at Stanford's annual security workshop next Monday. I 
believe it will be streamed on youtube, and you may find the other 
presentations interesting as well 
(http://forum.stanford.edu/events/2017security.php). The workshop is aimed at a 
non-specialist audience, but I still hope to get to much of the content I meant 
to present at ietf.

thanks,
~saba
________________________________
From: Ben Laurie <[email protected]<mailto:[email protected]>>
Sent: Monday, March 27, 2017 2:48:11 AM

To: Saba Eskandarian
Cc: [email protected]<mailto:[email protected]>
Subject: Re: [Trans] Privacy-preserving proof of sct exclusion



On 27 March 2017 at 05:16, Saba Eskandarian 
<[email protected]<mailto:[email protected]>> wrote:

Thanks for the prompt feedback! I'll make sure to address these comments in my 
talk, and I'm looking forward to discussing design options in person. I suspect 
that the flexibility of the tools and techniques we use as well as the 
associated engineering and privacy tradeoffs will make for an interesting 
discussion.

Afraid I won't be there, but looking forward to hearing more.



Thanks,

~saba

________________________________
From: Ben Laurie <[email protected]<mailto:[email protected]>>
Sent: Sunday, March 26, 2017 9:46:21 AM
To: Saba Eskandarian
Cc: [email protected]<mailto:[email protected]>
Subject: Re: [Trans] Privacy-preserving proof of sct exclusion



On 25 March 2017 at 22:39, Saba Eskandarian 
<[email protected]<mailto:[email protected]>> wrote:

Hello,

I'm on the agenda for Tuesday's meeting to share a privacy-preserving proof of 
sct exclusion from a log (I think Eran alluded to this work in a message a 
while ago).

My posted slides will not include many words, so I wanted to share a link to 
the preprint of our academic paper on the subject in case anyone wants to read 
the details there. The paper is targeted at a somewhat different audience, but 
it can be found here: https://arxiv.org/abs/1703.02209

Thanks and looking forward to meeting you all next week!

Cool, but I immediately see a problem - you require logs to be in timestamp 
order, but they aren't. I can't immediately think of a way to get that property 
without also considerably increasing time to inclusion in the log.

That seems undesirable - in fact, we're trying to go the other way, i.e. reduce 
time to inclusion, in general.

Also, engineering reality doesn't change, so increasing time to inclusion is 
also likely to increase MMD.

Secondly, its interesting, but doesn't seem particularly useful: when an SCT 
corresponds to a cert that has not been included, you want to reveal the cert, 
not hide it. What you want to hide is who is revealing it.


~saba

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