Introduction

Introduction to Proof of Location

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Proof of Location is a decentralised proof of "geolocation" which can be used to validate the geographic location of a "prover" device connected to Internet.

tl;dr

A prover (a node providing storage or compute or any DePIN service) asserts or claims their geographic location. This claim is verified by a network of watchtowers (or challengers) : decentralized set of nodes globally). This protocol relies on analyzing internet latency to determine the prover's location .

How does it work?

The protocol involves two key steps:

• Calibration

• Measurement

Calibration Phase

1. The protocol comprises a prover, whose location is to be validated and a decentralized set of watchtowers, whose location are known a priori

2. In calibration phase, the challengers measure Internet delay to each other via application layer UDP pings

3. A challenger then calibrates delay to distance mapping for itself using the delay measurements and the location of other challengers

Measurement Phase

1. In the measurement phase, the location claim of the prover is validated

2. The challengers measure delay to the prover using application layer UDP pings

3. Using the delay to distance mapping obtained during calibration phase, each challenger outputs a region where the prover can be present

4. Our protocol aggregates the output across different challengers and then outputs the maximum distance that the prover can be from its claimed location

Key Parties Involved

1. Payer: A party who pays for the challenge and starts one

2. Prover: The device connected to Internet whose location needs to be validated

3. Blockchain full-node: Decentralised ledger for recording all the challenge requests and outcomes

4. Challengers: A pool of servers that validate the location claim of the prover

5. Challenge coordinator: Centralised services for

   1. Communication between the parties

   2. Computing challenge meta data; and

   3. Cnteracting with the ledger

6. Broker: Centralized API service layer

Functional description

Functionally the different components involved in Proof of Location challenge are similar to that of Proof of Backhaul. The different steps in a Proof of Location challenge remain similar to the Proof of Backhaul, except during challenge execution, the measurement phase described above to validate prover's location is carried out instead of measuring the backhaul in Proof of Backhaul.

Trust and Threat Model (current)

The trust assumptions for challenge coordinator remain same to Proof of Backhaul

Prover

1. The prover can claim a false location

2. The prover can inflate the ping delays to the challenger during measurement phase of challenge execution

Challengers

1. In current version of Proof of Location, the challengers are a mix of trusted and trust-free nodes.

   1. They report their correction location

   2. They do not inflate delays to other challengers in calibration phase

   3. They use a correct delay to distance mapping in measurement phase

2. In future, our Proof of Location protocol will be able to tolerate a certain fraction of adversarial challengers, where the above trust assumptions will be relaxed