Subject: [Privacy-pass] Details about PrivateStats

From: Subodh Iyengar <[email-masked]>
Date: Fri, 15 Jan 2021 15:20:37 +0000

We presented the PrivateStats system at Real World Crypto yesterday we've been experimenting with at Facebook.

Here's a link to the paper https://research.fb.com/privatestats and also a link to the talk https://www.youtube.com/watch?t=48&v=4eKwlSqGUi4&feature=youtu.be

The paper and talk details some of the challenges productionizing a PrivacyPass style VOPRF.
We also introduce a new construction to derive an attribute based VOPRF which is compatible with PrivacyPass VOPRFs.

TL;DR: we change the way we derive the public key for the underlying VOPRF. An attribute (eg. a day or anything) is mapped -> {bit vector}. Then an attribute specific key is derived from the bit vector. The public key can be used directly in the VOPRF. Someone could later check that the public key was correctly derived from the attribute.

An attribute based VOPRF might be a good addition to privacypass and allow binding attributes to the Public Keys used for PrivacyPass VOPRFs, and would love to chat more about developing this

Thanks,
Subodh