Anonymous Tokens with Private Metadata Bit

Ben Kreuter; Tancrède Lepoint; Michele Orrù; Mariana Raykova

Paper 2020/072 Original: eprint.iacr.org/2020/072 ↗

Anonymous Tokens with Private Metadata Bit

Ben Kreuter

Tancrède Lepoint

Michele Orrù

Mariana Raykova

Abstract

We present a cryptographic construction for anonymous tokens with private metadata bit, called PMBTokens. This primitive enables an issuer to provide a user with a lightweight, single-use anonymous trust token that can embed a single private bit, which is accessible only to the party who holds the secret authority key and is private with respect to anyone else. Our construction generalizes and extends the functionality of Privacy Pass (PETS’18) with this private metadata bit capability. It is based on the DDH and CTDH assumptions in the random oracle model and provides unforgeability, unlinkability, and privacy for the metadata bit. Both Privacy Pass and PMBTokens rely on non-interactive zero-knowledge proofs (NIZKs). We present new techniques to remove the need for NIZKs, while still achieving unlinkability. We implement our constructions and we report their efficiency costs.

Metadata

Available format(s): PDF
Category: Cryptographic protocols
Publication info: Preprint.
History: 2022-04-21: last updated; 2020-01-23: published
Short URL: https://ia.cr/2020/072
License: https://creativecommons.org/licenses/by/4.0/

BibTeX

@misc{cryptoeprint:2020/072,
      author = {Ben Kreuter and Tancrède Lepoint and Michele Orrù and Mariana Raykova},
      title = {Anonymous Tokens with Private Metadata Bit},
      howpublished = {Cryptology {ePrint} Archive, Paper 2020/072},
      year = {2020},
      url = {https://eprint.iacr.org/2020/072}
}