Re: New Work Item Proposal: Revocation List 2020

On 5/1/20 6:18 PM, Daniel Hardman wrote:
> How is this privacy-preserving? Can you say some more about that?

Mike Lodder wrote:
> I’m failing to see how this is privacy preserving? The verifier would
> need to know the index from the credential into the revocation list.
> The point of preserving privacy is that the verifier doesn’t know the
> index. This sounds just like checking an RCL in another form. There’s
> no herd privacy here at all. If I had a list of 10k or 100k doesn’t
> matter. If the relying party knows my index, there’s no privacy

Sounds like we're getting ready to enter a debate on the definition of 
"privacy" and "privacy preserving", and I doubt that we'll come out on 
the other side having agreed to a single definition. :)

So let me start by asserting that there are degrees of privacy and 
degrees of privacy preserving. I expect this method is further away from 
where both of you might want to be on those scales.

There is also a fundamental assumption that this revocation mechanism 
assumes: There will be at least one identifier on the VC, like a 
driver's license number, or a corporate tax ID number, or a postal 
address, or payment details.

If your goal is almost complete anonymity -- do not use this revocation 
method. :)

If your goal is achieving varying levels of privacy that one might 
expect when handing over a driver's license, corporate paperwork, 
shipping instructions, or making a payment, then this revocation method 
may be useful to you.

Here are the design goals for Revocation List 2020:

* Enable an issuer to publish revocation lists on their existing
   infrastructure without knowing which holder's revocation status
   is being checked.
* Enable a holder to have some assurance of herd privacy.
* Enable a verifier to cache large populations of revocation
   data without having to phone home constantly.
* Enable a verifier to cloak their requests for revocation
   information by using Content Distribution Networks or network
   proxies to hide their requests.
* Enable a holder to deliver a fresh revocation list, avoiding a
   verifiers need to go out to the network and pull the revocation list
   from the issuer (revocation lists are just VCs afterall).

All of these things work to preserve privacy.

Are they as privacy preserving as Sovrin and Evernym's solutions? Given 
that the VC contains an identifier of some sort anyway, I'd argue that 
it's just as privacy preserving.

-- manu

-- 
Manu Sporny (skype: msporny, twitter: manusporny)
Founder/CEO - Digital Bazaar, Inc.
blog: Veres One Decentralized Identifier Blockchain Launches
https://tinyurl.com/veres-one-launches

Received on Saturday, 2 May 2020 02:04:42 UTC