This paper tackles the challenge of reliably determining the geo-location of
nodes in decentralized networks, considering adversarial settings and without
depending on any trusted landmarks. In particular, we consider active
adversaries that control a subset of nodes, announce false locations and
strategically manipulate measurements. To address this problem we propose,
implement and evaluate VerLoc, a system that allows verifying the claimed
geo-locations of network nodes in a fully decentralized manner. VerLoc securely
schedules roundtrip time (RTT) measurements between randomly chosen pairs of
nodes. Trilateration is then applied to the set of measurements to verify
claimed geo-locations. We evaluate VerLoc both with simulations and in the wild
using a prototype implementation integrated in the Nym network (currently run
by thousands of nodes). We find that VerLoc can localize nodes in the wild with
a median error of 60km, and that in attack simulations it is capable of
detecting and filtering out adversarial timing manipulations for network setups
with up to 20% malicious nodes.

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