ConTrib

Abstract

Preventing the abuse of resources is a crucial requirement in shared-resource systems. This concern can be addressed through a centralized gatekeeper, yet it enables manipulation by the gatekeeper itself. We present ConTrib, a decentralized mechanism for tracking resource usage across different shared-resource systems. In ConTrib, participants maintain a personal ledger with tamper-proof records. A record describes a resource consumption or contribution and links to other records. Fraud, maintaining multiple copies of a personal ledger, is detected by users themselves through the continuous exchange of records and by validating their consistency against known ones. We implement ConTrib and run experiments. Our evaluation with up to 1'000 instances reveals that fraud can be detected within 22 seconds and with moderate bandwidth usage. To demonstrate the applicability of our work, we deploy ConTrib in a Tor-like overlay and show how resource abuse by free-riders is effectively deterred. This longitudinal, large-scale trial has resulted in over 137 million records, created by more than 86'000 volunteers.