Introduction to Proof of Location – FOAM

The case for alternative location systems

At FOAM, we believe people should own their personal information, controlling when and with whom they choose to share their location. Our team is committed to solving this, building spatial protocols, standards, and applications that offer a higher level of security and more resiliency than conventional geospatial technologies. With our recent work on the Crypto Spatial Coordinate standard and Spatial Index visual block explorer - powered by our open source purescript web3 library - we introduced some of the essential components we will be using to develop FOAM’s core project, a decentralized protocol for Proof of Location.

Our approach inverts the current market for geospatial data, which relies on bulk collection of information for targeting and resale, by creating a new location markets that offer a significantly improved security model. Proof of Location allows users and autonomous agents to privately record authenticated location data at times of their choosing, and then reveal their personal information at their discretion, by presenting a fraud-proof location claim.

Features of FOAM Proof of Location

1.Trustless: Byzantine fault tolerant clock synchronization
2. Independent: Does not rely on GPS
3.Open: Anyone can utilize the network or offer utility services
4.Accountable: Economics structured to ensure honest behavior, verified with fraud proofs
5.Incentivized: Service providers remunerated for extending localization and verification zones

The purpose of this post is to introduce many of the problems posed by insecure geolocation and to offer insight into our solution: a Proof of Location system that maintains Byzantine consensus throughout a distributed network of synchronized clocks, while creating markets for local generation of triangulated positional data.

However, before we describe the design of FOAM’s Proof of Location protocol, we will first make a case for why a system like this is needed.

The Vulnerabilities of GPS

GPS is the world’s premier Global Navigation Satellite System (GNSS), consisting of 31 satellites launched by the U.S. military and made available for civilian and commercial use. GPS has become a ubiquitous tool, recently dubbed as ” The Technology That Envelops Our Cities - and Brains ” by Alphabet’s Sidewalk Labs. What may not be immediately apparent, is that GPS technology works through time as much as it does space. Inside each satellite is a high-precision atomic clock, which sync regularly to master control stations on the ground. GPS receivers, common in today’s smart phones, must pick up time-stamped signal data from a minimum of four overhead satellites. By using time stamps to calculate the time of arrival, a receiver can calculate a triangulated position.

Ordinarily, GPS is incredibly reliable, so much so that we have collectively become dependent on a functioning geopositioning system. However, problems and attack vectors with this system have become increasingly evident. Recent articles are highlighting how the entire global financial system depends on GPS. The New York Stock Exchange uses GPS to time automated computer trades, ATM’s and credit card transactions require location data, even the electrical grid relies on GPS synchronized time stamps to deliver electricity without causing power surges, not to mention the transportation, navigation, and mobility use cases of the technology.

Civil GPS is unencrypted, it has no proof-of-origin or authentication features, and despite dire warnings in the mainstream since at least 2012, the system remains extremely susceptible to fraud, spoofing, jamming, and cyberattack. Operational Control System (OCX), the next generation of GPS “will be the first satellite control system designed after the advent of significant jamming and other cyber threats.” However, the project has been continuously delayed, with a scheduled launch date now in 2022. Even so, the OCX design fails to address vulnerabilities, “GPS competitiveness as a worldwide civil system will diminish.”

The limitations of GPS requires at least four beacon signals to be overhead, which makes indoor localization nearly impossible. Urban density and skyscrapers also cause difficulties in receiving four messages and the issue of multi-path signals occurs within the vicinity of high rise buildings, Further, for a device, it can take multiple minutes to acquire an accurate coordinate. When it comes to power consumption, GPS is a drain on battery and is not feasible for low powered IoT devices.

In sum, the issues with depending on GPS for verified location are:

·A Single Point of Failure, centralized
·Does not penetrate well indoors or underground
·Urban Density increases signal Multipath
·Energy intensive components are not suitable for devices with long maintenance cycles
·Susceptible to signal jamming
·Spoofing, i.e deceive a GPS receiver by broadcasting incorrect GPS signals

GPS is not suitable for blockchain based applications that will need precise and reliable location. For example, Boeing recently announced a blockchain-based GPS data store in case of GPS failure during a flight. Proof of Location can provide consensus on whether an event or agent is verifiably at a certain point in time and space.

Low Power Wide Area Networks

There are a number of radio technologies and techniques for localization/positioning systems without the use of GPS. These alternative position systems use a range of localization processes and techniques, which include Time of Arrival (TOA), Time Difference of Arrival (TDOA), Angle of Arrival (AOA) and Received Signal Strength (RSS). Among WiFi, RFiD and cellular radio a new class of radio that is emerging and highly promising for internet of things devices called Low Power Wide Area Networks (LPWAN). LPWAN can offer the low power and longer battery life of bluetooth with the range of cellular. The trade-off is low throughput for high-capacity networks suitable for scaling. Another benefit of low power transmission is the access it allows to the unlicensed radio spectrum. LPWAN radios can operate on free radio waves without needing a license to offer coverage. Deploying a LPWAN, just like a blockchain, is permissionless.

This technology is at the core of the FOAM vision for its ability to scale, cover large distances and remain available due to the low power. A node on the FOAM network will need to offer accurate time synchronization over radio transceivers. This kind of beacon is called a Zone Anchor. Four or more Zone Anchors form a Zone, the quorum that maintains clock sync for a given region. Once synchronized, the Zone can determine the location of a requesting node by using time of arrival measurements to verifiably triangulate position.

One of the most promising new radios is a called LoRa, a physical layer technology that can travel 5-15km at 150 MHz and 1 GHz bands, which can provide bidirectional communication with a special chirp spread spectrum (CSS) techniques for long range with properties that make it harder to detect or jam. There is already the enterprise consortium called the LoRa Alliance, designing an open standard and defining architecture and layers above the LoRa physical layer. Further there are open development communities in major cities around LoRa open libraries centered around the Things Network. Because these radios allow for bidirectional communication, mesh network topology significantly extends range.

While this technology is available today, what is missing are the economic incentives to purchase, install and maintain a network of beacons. Just as Bitcoin, Ethereum, and many other blockchains “hired” miners to run and operate the network, crypotoeconomic incentives are needed to grow a decentralized alternative to GPS. Nodes on FOAM are mining triangulations. Further, with smart contracts, Zone operators participating in FOAM can enter into Service Level Agreements (SLA) and back these agreements with token safety deposits into a smart contract. This SLA enables autonomous service providers to maintain nodes, promising to do so with a bond and extend coverage to offer services to a marketplace at a profit. Enabling SLA contracts for location verification services is a core component to the thinking behind the FOAM Proof of Location protocol.

FOAM Proof of Location

Time and Space are intricately intertwined. Our approach to Proof of Location rests on an autonomously self-stabilizing time synchronization protocol that ensures continuity of a distributed, Byzantine fault tolerant (BFT) clock. With a high-precision BFT clock signal, the network can use the relative geometry between beacons to compute a node’s distance, thereby enabling a secure, spatially distributed location system.

Zone Anchor beacons running the FOAM protocol will need to provide accurate time synchronization for a set period of time in order to not be seen as faulty. A distributed system is Byzantine fault tolerant when the coordination of untrustworthy participants will always convey honest information, given more than 2/3 act honestly. It is important that a time synchronization is able to self-stabilize if a number of nodes are broken or malicious.

All radio frequency (RF) location systems rely on clock precision. The most accurate approaches require clock synchronization. We use a BFT clock synchronization algorithm to provide the best possible support for RF Time of Flight algorithms. The Proof of Location protocol is open for Zones to autonomously form and operate as utility providers that compete for transactions fees by providing location verification services.

We use crypto-economic staking incentives to grow network coverage and utilize a validator set for fraud proofs, and enforce protocol rules. Safety deposits allow for attributable byzantine behavior in the form of slashing conditions. The system further encompasses a data store and validator set, the specifics of these mechanisms will be detailed in a forthcoming post.

The case for strong Proof of Location can be made not only for future and speculative blockchain use cases, but can compliment current and existing ones as well. For example, Proof of Location can be applied to file storage to determine if the data on disks are in different places. Similarly, Proof of Stake protocols that claim a global and distributed validator set can make certain the geographic global distribution of validators. With Proof of Location stablecoin projects can sharpen their scope to keeping nominal spending constant within a designated geo-fenced area.

These examples are only the beginning. Major use cases of Proof of Location with blockchain security will come in the form of distributed fleets of autonomous vehicles that need real time, fault tolerate, shared mapping of a determined area. Even IoT data markets that will need to attest the data provenance can leverage the FOAM protocol. ” Ethereum Innovators Are Reviving the Fight for Net Neutrality ” by retooling mesh networks for a more decentralized internet and ISP markets. To aid these ambitions precise time and accurate location information provided by FOAM will remain key to obtaining a robust and alternative internet networks.

While there is no “location specific hash function in nature” it is viable to incentivize an autonomous and self stabilizing system of nodes that can synchronize their clocks to offer secure location verification with accountability enforced by smart contract protocol rules. This is what we are working on at FOAM and believe that such a system is needed as a crucial infrastructure in our decentralized future and can open new marketplaces of privacy preserving location data. Over the coming weeks we will be sharing detailed information about our token mechanism and further technical breakdowns of Proof of Location as well as a new white paper.


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