Alibi Routing

Abstract

There are several mechanisms by which users can gain insight into where their packets have gone, but no mechanisms allow users undeniable proof that their packets did not traverse certain parts of the world while on their way to or from another host. This paper introduces the problem of finding "proofs of avoidance": evidence that the paths taken by a packet and its response avoided a user-specified set of "forbidden" geographic regions. Proving that something did not happen is often intractable, but we demonstrate a lowoverhead proof structure built around the idea of what we call "alibis": relays with particular timing constraints that, when upheld, would make it impossible to traverse both the relay and the forbidden regions. We present Alibi Routing, a peer-to-peer overlay routing system for finding alibis securely and efficiently. One of the primary distinguishing characteristics of Alibi Routing is that it does not require knowledge of-or modifications to-the Internet's routing hardware or policies. Rather, Alibi Routing is able to derive its proofs of avoidance from user-provided GPS coordinates and speed of light propagation delays. Using a PlanetLab deployment and larger-scale simulations, we evaluate Alibi Routing to demonstrate that many source-destination pairs can avoid countries of their choosing with little latency inflation. We also identify when Alibi Routing does not work: it has difficulty avoiding regions that users are very close to (or, of course, inside of).

VerLoc: Verifiable Localization in Decentralized Systems

“…Establishing Secure Connections Trusted connections are an important building block of security-oriented systems. DeTor [40,42] uses a timing-based analysis technique to identify Tor circuits through untrusted areas. In contrast to hardware-based solutions [4] or routing protocol adaptions [45], a timing based approach can be deployed in decentralized systems, and allows for adjustable decisions [35].…”

On the Challenges of Geographical Avoidance for Tor

“…In other words, the additional distance, and hence time, required to traverse the forbidden area is higher than the measured RTT would allow. This concept was originally introduced in the context of Alibi Routing [29], where single hops were checked and later extended to three-hop connections to fit the needs of Tor.…”

“…In particular, DeTor calculates its decision threshold based on a detour to the forbidden area on both directions of a round-trip. This is a critical misconception introduced when the authors transitioned their technique from one-way connections [29] to Tor circuits. A negligent doubling of the necessary distance overestimates the required time.…”

Neural Network Prediction of Censorable Language

“…There have been significant efforts to develop strategies to detect and evade censorship. Most work, however, focuses on exploiting technological limitations with existing routing protocols (Leberknight et al, 2012;Katti et al, 2005;Levin et al, 2015;McPherson et al, 2016;Weinberg et al, 2012). Research that pays more attention to linguistic properties of online censorship in the context of censorship evasion include, for example, Safaka et al (2016) who apply linguistic steganography to circumvent censorship.…”