BFT-PoLoc: A Byzantine Fortified Trigonometric Proof of Location Protocol using Internet Delays (2403.13230v2)

Abstract: Internet platforms depend on accurately determining the geographical locations of online users to deliver targeted services (e.g., advertising). The advent of decentralized platforms (blockchains) emphasizes the importance of geographically distributed nodes, making the validation of locations more crucial. In these decentralized settings, mutually non-trusting participants need to {\em prove} their locations to each other. The incentives for claiming desired location include decentralization properties (validators of a blockchain), explicit rewards for improving coverage (physical infrastructure blockchains) and regulatory compliance -- and entice participants towards prevaricating their true location malicious via VPNs, tampering with internet delays, or compromising other parties (challengers) to misrepresent their location. Traditional delay-based geolocation methods focus on reducing the noise in measurements and are very vulnerable to wilful divergences from prescribed protocol. In this paper we use Internet delay measurements to securely prove the location of IP addresses while being immune to a large fraction of Byzantine actions. Our core methods are to endow Internet telemetry tools (e.g., ping) with cryptographic primitives (signatures and hash functions) together with Byzantine resistant data inferences subject to Euclidean geometric constraints. We introduce two new networking protocols, robust against Byzantine actions: Proof of Internet Geometry (PoIG) converts delay measurements into precise distance estimates across the Internet; Proof of Location (PoLoc) enables accurate and efficient multilateration of a specific IP address. The key algorithmic innovations are in conducting ``Byzantine fortified trigonometry" (BFT) inferences of data, endowing low rank matrix completion methods with Byzantine resistance.

• The paper presents BFT-PoLoc, a Byzantine-fault-tolerant protocol enabling secure node location proof in decentralized systems using internet delays, comprising PoIG for robust distance estimation and PoLoc for location verification.
• PoIG uses ratio-based filtering and matrix completion achieving over 95% accuracy in distance under attacks, while PoLoc uses BFT trigonometry for location verification and uncertainty estimation.
• Evaluated on Ethereum and Solana, BFT-PoLoc achieves location accuracy within 100 km and effectively resists spoofing and VPNs, offering robust support for secure decentralized services.

BFT-PoLoc: A Byzantine Fault Tolerant Proof of Location Protocol

The paper "BFT-PoLoc: A Byzantine Fortified Trigonometric Proof of Location Protocol using Internet Delays" introduces a novel protocol that allows nodes in decentralized internet platforms to prove their geographical locations securely and resiliently against Byzantine attacks. This capability is critical for maintaining decentralization, regulatory compliance, and effective service delivery in blockchain-based systems. The need for such solutions arises due to the potential misrepresentation of locations by participants using VPNs or by manipulating internet delays to gain unearned advantages in decentralized networks.

The core of this protocol builds on the resilience against Byzantine actions, which are characterized by nodes behaving arbitrarily or maliciously. The authors propose two complementary protocols: Proof of Internet Geometry (PoIG) and Proof of Location (PoLoc). PoIG is designed to derive distance estimates from delay measurements that are robust against Byzantine manipulations. PoLoc is employed to verify the claimed geographical location of a node through Byzantine fault-tolerant computations.

Methodological Advancements

In addressing the challenge of Byzantine fault tolerance in geolocation, the authors introduce a system that integrates cryptographic verification processes with geometric constraints. This integration enables the accurate conversion of internet delays into distance estimations while providing mechanisms for robust multilateration of node locations. Key algorithmic components include:

1. Proof of Internet Geometry (PoIG):
   • Implements ratio-based filtering to mitigate inflated delay and distance reports.
   • Utilizes robust matrix completion methods to construct efficient and reliable delay-to-distance mappings.
   • Maintains over 95% accuracy under Byzantine distance inflation attacks given a majority of honest challengers.
2. Proof of Location (PoLoc):
   • Employs Byzantine Fortified Trigonometry (BFT) to perform multilateration while mitigating adversarial disruptions.
   • Outputs the maximum potential deviation of a node from its claimed location (the "uncertainty") based on geometric inferences.

Implementation and Results

The BFT-PoLoc system was evaluated using a delay-based geolocation service integrated into both the Ethereum and Solana blockchains. The system demonstrated high effectiveness in identifying the true geographical area of nodes, achieving a location accuracy within 100 km for a considerable spatial extent. The protocol was demonstrated to robustly handle manipulation attempts, including location spoofing and VPN usage. Its performance exceeded the capabilities of traditional linear mapping methodologies used in delay-based geolocation, offering enhanced resistance to Byzantine challenges and adversarial behavior.

Implications and Future Work

The research presented in this paper has substantial implications for the design and operation of blockchain-based systems, notably enhancing location verification's robustness, necessary for ensuring the decentralization and integrity of distributed services. Practically, this protocol can support robust network topologies required for distributed file storage, VPN services, and distributed wireless networks in the blockchain ecosystem.

The proposed PoIG and PoLoc protocols advance the understanding and applicability of geolocation in trustless settings. Further development could explore deeper integrations with other consensus mechanisms or improve the efficiency and reduction of computational overhead. Expanding the adversarial model to include dynamic threats and environmental variables can further refine the system for broader applications. This research presents a significant step toward overcoming the inherent challenges of proving locations in decentralized networks, setting a foundation for more secure and resilient internet service models in the future.