INTRODUCING PROOF-OF-WORK DEFENSE FOR ONION SERVICES

Summary from the TLDR newsletter

Tor's Proof-of-Work (PoW) defense for Onion services is designed to prioritize verified traffic as a deterrent against denial-of-service (DoS) attacks. Tor Onion services are vulnerable to DoS attacks as Tor obfuscates IP addresses. PoW defense will start prompting incoming client connections to perform a number of successfully more complex operations when an Onion service is under stress. The Onion service will then prioritize connections based on the effort level demonstrated by the client. This will thwart DoS attacks without compromising user privacy.