# Pudding: User Discovery for Anonymity Networks Privacy-preserving username lookup system for darknets - **Source:** [Martin Kleppmann](https://martin.kleppmann.com) - **Published:** 2024-07-05 - **Topic:** [Software & Engineering](https://brifing.si/c/engineering) - **Original article:** - **On Brifing:** https://brifing.si/s/86672ce8-db35-4b63-8843-57e49b8837f0 ## The Core Challenge of Anonymity Networks Systems like Tor and Nym are designed to conceal users' communications, but require manual exchange of complex cryptographic keys for peer discovery. This creates significant usability barriers that hinder mass adoption, despite the critical privacy benefits these networks provide for whistleblowers and activists. ## Pudding's Innovative Approach Pudding introduces familiar identifiers like email addresses to anonymity networks, enabling user discovery without leaking metadata about who's communicating. The system goes further by even hiding whether a username exists in the network, providing stronger privacy guarantees than conventional solutions. ## Academic Recognition Presented at the prestigious IEEE Security and Privacy Symposium, Pudding's research received positive attention for solving the discoverability problem in anonymity networks. The paper provides formal security proofs while maintaining practical usability - a rare combination in privacy research. ## Adoption Lessons from Messaging Apps The success of WhatsApp and Signal demonstrated that user-friendly discovery (via phone numbers) is crucial for encryption adoption. Pudding applies similar principles to anonymity networks using email-based identifiers, creating a practical solution for high-risk users like journalists operating under repressive regimes. ## Technical Implementation Currently a research prototype built on Loopix/Nym architecture, Pudding isn't production-ready but shows promise as a transport layer for decentralized collaboration tools. The team hopes mainstream anonymity networks might integrate similar functionality, bridging the gap between security and usability. ## Balancing Security and Usability Pudding addresses a fundamental tension in privacy technologies - the tradeoff between security and accessibility. By learning from PGP's failures, it demonstrates how strong encryption can coexist with intuitive interfaces, potentially bringing anonymity protections to broader audiences without compromising security. ## Sources covering this story - http://martin.kleppmann.com/2024/07/05/pudding-user-discovery-anonymity-networks.html — --- _Summary written by Brifing from the original reporting. Copyright in the original article belongs to its publisher; read the full piece at the link above._