Defense Against Protocol Level Attack in Tor Network using Deficit Round Robin Queuing Process

Abstract

Among different types of network, Tor network is mostly referred as an onion-routing network which enables the anonymous communication and supports TCP applications over the network. The onion-routing is utilized by the Tor network for transmitting the information of users via virtual circuits which are created by several successive relays. The performance and security of the anonymous communication in Tor network have been improved by using Novel Traffic Dividing and Scheduling (NTDS) mechanism. Normally, this mechanism was used for preventing the basic versions of sniper attacks in the Tor network. On the other hand, protocol-level attacks were not possible to prevent since some malicious entry router may duplicate, alter, insert or delete the TCP stream cells from the sender. This may cause cell recognition errors at the exit router and these cell recognition errors were recognized at the destination which helps to identify the sender. Hence, in this article, a defense mechanism called Mid-DRRQ is proposed for protocol-level attacks against Tor network. In Mid-DRRQ mechanism, the protocol-level attacks are prevented by using indistinguishability obfuscation model which generates the fake traffic within the middle relay. This fake traffic is allowed on outgoing connections without any cover traffic. Moreover, the outgoing connections of middle relays are controlled by using Deficit Round Robin queuing process. Finally, the simulation results show that the proposed mechanism effectively prevents the protocol-level attacks against Tor network.