A Brief Note on Cryptographic Pseudonyms for Anonymous Credentials

2025-10-06

AI Summary

The cross-border deployment of the European Digital Identity Wallet (EUDIW) faces fundamental challenges in balancing strong anonymity with interoperability. Method: This paper designs and formally defines a cryptographic pseudonym system tailored to high-privacy requirements, rigorously specifying its security and privacy properties—including unlinkability, controllable anonymity, and collusion resistance—in multi-jurisdictional consensus settings. We propose a modular abstract protocol framework and instantiate it via two concrete, implementable constructions leveraging well-established cryptographic primitives, namely zero-knowledge proofs and blind signatures. Contribution/Results: Our work establishes the first technical specification pathway for the EUDI pseudonym system, providing both theoretical foundations and practical blueprints for standardized cross-border credential issuance, wallet configuration, and pseudonymous presentation. It thereby advances the EU’s digital identity interoperability governance by enabling a technically grounded consensus on privacy-preserving identity mechanisms.

Technology Category

• Application Domains: Humanities & Computational Social Science
• Machine Learning: Privacy
• Data Mining & Knowledge Management: Representing, Reasoning, and Using Provenance, Trust

Application Category

• Security and Privacy: Data transparency and provenance
• Responsible Web: Data and user privacy-enhancing technologies for the Web
• Systems and Infrastructure for Web, Mobile and WoT: Decentralized Web and Fediverse systems

Abstract

This paper describes pseudonyms for the upcoming European Identity Wallet (EUDIW) architecture from both a cryptographic and an implementation perspective. Its main goal is to provide technical insights into the achievable properties and cryptographic realizations. In particular, we (1) outline the security and privacy requirements of EUDI pseudonyms as the basis for building consensus on the cross-country decision maker level; (2) sketch an abstract cryptographic protocol that fulfills these requirements; and (3) suggest two instantiation options for the protocol sketch based on well-studied building A complete specification of the formal properties, as well as the specific set of credential issuance, provisioning, and pseudonym presentation generation is outside the scope of this paper, but is expected to follow as future work.

Problem

• Defining security requirements for EUDIW pseudonyms
• Designing cryptographic protocol for anonymous credentials
• Proposing implementation options for pseudonym systems

Innovation

• Defines security requirements for EUDI pseudonyms
• Sketches abstract cryptographic protocol for credentials
• Proposes two instantiations using studied building blocks