Explore the concept of truly anonymous credentials using modern cryptography in this 44-minute conference talk from Security BSides London. Dive into the world of anonymous networks like Tor and I2P, and learn about a novel authentication system based on homomorphic properties of elliptic curve cryptography and zero knowledge proofs called "Linkable Ring Signatures." Discover how this system allows users to add their public key to a larger group of existing public keys, creating a "ring" that enables anonymous signing while maintaining verifiability. Understand the mathematical principles behind preventing spam and DoS attacks without compromising user anonymity. Follow along as the speaker walks through cryptographic primitives, demonstrates a Tor/I2P-based anti-spam anonymous forum, and explains the security implications of this innovative approach. Gain insights into elliptic curves, modular groups, Schnorr signatures, and the challenges of maintaining privacy in anonymous networks.