Notes on anonymous credentials

Thu, 26 Mar 2020 20:06:25 +0000

Best anonymous credentials that don’t use pairings:

Single show, no attributes, symmetric issuer: Privacy Pass; uses VOPRFs

Multi show, attributes, symmetric issuer: CMZ14 (original, https://eprint.iacr.org/2013/516)/CPZ19 (group element attribute variant, https://eprint.iacr.org/2019/1416); uses “algebraic MACs” and categorically supercedes U-Prove

Single show, attributes, publicly verifiable: Anonymous Credentials Light; uses an Abe signature variant

For multi-show with attributes and public verifiability, as far as I know you need to use pairings to get randomizable signatures. The best general credential of this type might still be the first real one, CL04 (https://cs.brown.edu/people/alysyans/papers/cl04.pdf) but probably now you’d instantiate it with Pointcheval-Sanders signatures (PS16, https://eprint.iacr.org/2015/525 + PS18, https://eprint.iacr.org/2017/1197 tweaked for better proofs) which allows for constant-size credentials.

Notes on threshold signature schemes

Fri, 18 Oct 2019 02:33:40 +0000

A threshold signature allows a subset t of a group of n possible signers to collectively produce a signature for the entire group. The simplest ones tend to use some distributed key generation (“DKG”) based on verifiable secret sharing (“VSS”) to construct the keys and secret inputs to a Schnorr signature in a distributed manner. There have been a lot of these, and recalling all the Feldman-this and Pedersen-that gets confusing. The following seem to be the core papers in the field of discrete-log threshold signatures:

Brain Dumps on gtank writes here

Notes on anonymous credentials

Notes on threshold signature schemes