CS-BuFLO: A Congestion Sensitive Website Fingerprinting Defense

Website fingerprinting attacks[10] enable an adversary to infer which website a victim is visiting, even if the victim uses an encrypting proxy, such as Tor[19]. Previous work has shown that all proposed defenses against website finger-printing attacks are ineffective[6, 4]. This paper advances the study of website fingerprinting defenses by first laying out the complete specifications of the Congestion-Sensitive BuFLO scheme outlined by Cai, et al. [4]. CS-BuFLO, which is based on the BuFLO defense proposed by Dyer, et al.[6], was not fully-specified by Cai, et al, but has nonetheless at-tracted the attention of the Tor developers [16, 17]. Next, a full working implementation of CS-BuFLO is provided. Finally, a thorough evaluation of CS-BuFLO is performed using empirical data (rather than data from simulations). Our experiments find that Congestion-Sensitive BuFLO has high overhead (around 2.3-2.8x) but can get 6 × closer to the bandwidth/security trade-off lower bound than Tor or SSH. 1