TagIt: Tagging Network Flows using Blind Fingerprints

Flow fingerprinting is a mechanism for linking obfuscated network flows at large scale. In this paper, we introduce the first blind flow fingerprinting system called TagIt. Our system works by modulating fingerprint signals into the timing patterns of network flows through slightly delaying packets into secret time intervals only known to the fingerprinting parties. We design TagIt to to enable reliable fingerprint extraction by legitimate fingerprinting parties despite natural network noise, but invisible to an adversary who does not possess the secret fingerprinting key. TagIt makes use of randomization to resist various detection attacks such as multi-flow attacks. We evaluate the performance and invisibility of TagIt through theoretical analysis as well as simulations and experimentation on live network flows.