Spatial Proof-of-Presence

At its core, Spatial Proof-of-Presence relies on cryptographic attestations from trusted hardware or secure enclaves (like TPMs or Secure Elements). The device generates a signed statement containing a timestamp and verified location data, which is then anchored to a blockchain. This creates a tamper-proof record that proves the device, and by extension its user or asset, was physically present at the claimed coordinates.

Proofs can be generated using various trusted data sources, each with different precision and security trade-offs.

• GPS/GNSS with Spoof Resistance: Uses signals from satellite constellations, often enhanced with cryptographic signatures (e.g., Galileo OSNMA) to prevent spoofing.
• Cellular Triangulation: Verifies location relative to known cell tower coordinates.
• Wi-Fi/Bluetooth Beacons: Proximity to trusted, geographically fixed wireless access points.
• Geofencing Triggers: Event-based proofs generated when a device enters or exits a predefined virtual boundary.

Unlike centralized location services, Spatial Proof-of-Presence decentralizes trust. The verification logic is often encoded in a smart contract on a blockchain. The contract validates the cryptographic attestation against a set of consensus rules (e.g., trusted hardware manufacturers, approved location oracles). This removes reliance on a single authority and allows for permissionless verification by any network participant.

A critical feature is the binding of location to a specific, unforgeable moment in time. The proof is cryptographically linked to a block timestamp or a trusted time oracle. Combined with device-specific keys, this ensures the proof is non-transferable and non-replayable. A proof generated for Device A at Time T cannot be reused by Device B or re-submitted at Time T+1.

This technology enables applications that require verifiable physical presence.

• DePIN & Physical Work Verification: Proving a node or miner is operating in its designated geographic zone (e.g., for decentralized wireless or mapping networks).
• Supply Chain & Asset Tracking: Creating an immutable audit trail of a physical asset's journey.
• Location-Based NFTs & Gaming: Minting NFTs or triggering game events tied to real-world locations (e.g., Pokémon GO-like mechanics on-chain).
• Decentralized Identity (DID): Adding a verified location claim to a user's self-sovereign identity credentials.

Implementing robust Spatial Proof-of-Presence involves navigating several technical hurdles.

• Hardware Trust Root: Dependency on the security of the device's hardware secure element.
• Spoofing & Privacy Attacks: Defending against GPS signal simulation, proxy attacks, or privacy leaks from precise location data.
• Oracle Reliability: The security of the system depends on the reliability and decentralization of any external location oracles or time sources.
• Scalability & Cost: Generating and verifying cryptographic proofs on-chain can incur transaction fees and latency.

SPoP is foundational for DePIN networks, where contributors are rewarded for deploying and maintaining physical hardware like wireless hotspots or sensors. It cryptographically proves the device's operational location, preventing Sybil attacks where a single entity claims rewards for non-existent nodes. This enables trustless coordination for networks like Helium (5G/IoT) and Hivemapper (mapping).

This application mints non-fungible tokens (NFTs) or digital assets that are intrinsically tied to a geographic coordinate. To mint, a user must cryptographically sign a transaction from the verified GPS coordinates. This creates provably scarce digital artifacts for real-world places, used for:

• Geocaching and location-based games
• Commemorative tokens for events or landmarks
• Proof of attendance at physical venues

SPoP provides immutable, time-stamped records of an asset's journey through a supply chain. Each handoff or location update is verified on-chain, creating an auditable trail. Key applications include:

• Verifying ethical sourcing of materials (e.g., conflict-free minerals)
• Proving cold-chain compliance for pharmaceuticals
• Authenticating origin for luxury goods and agriculture

Projects can distribute tokens or rewards to users who physically visit specific locations, creating engaged local communities. The airdrop contract verifies the SPoP attestation before releasing funds. This is used for:

• Retail promotions and customer loyalty programs
• Tourism initiatives to drive foot traffic
• Event engagement with exclusive rewards for attendees

SPoP acts as a verifiable credential within a decentralized identity (DID) framework, proving a person's presence for KYC, employment, or membership. A user can selectively disclose location proofs without revealing other identity details. Use cases include:

• Proof of residency for services or voting
• Work verification for remote or gig economy jobs
• University attendance records

Smart contract logic can be conditioned on the verified location of a transaction signer. This enables Decentralized Autonomous Organizations (DAOs) or contracts that are only executable within a defined geographic boundary. Examples include:

• Local community DAOs for neighborhood governance
• Property-specific contracts for access control
• Regulation-compliant DeFi limited to certain jurisdictions

SPoP relies on a combination of zero-knowledge proofs (ZKPs) and digital signatures to create a verifiable claim about a user's location without revealing the exact coordinates or compromising privacy. The protocol typically involves:

• Location Signing: A trusted device (e.g., a smartphone with GPS) generates a cryptographic signature over a location-timestamp tuple.
• Proof Generation: A ZKP is constructed to prove the signature is valid and corresponds to a location within a defined geofence.
• Verification: Any network participant can verify the proof's validity on-chain without learning the underlying private data.

The integrity of a Spatial Proof depends on the security of the Trusted Execution Environment (TEE) or Secure Enclave within the user's device (e.g., Apple's Secure Enclave, Android's StrongBox). This hardware component:

• Isolates the signing keys and location data from the main operating system.
• Ensures the signed location attestation is generated by genuine hardware, not a software simulator.
• Provides resistance against common spoofing attacks, forming a root of trust for the entire proof system.

To enable privacy-preserving verification, precise coordinates are converted into a privacy-safe format using geohashing or S2 Cell indexing. This process:

• Discretizes the continuous geographic space into a grid of cells at a specific resolution.
• The ZK circuit is programmed to verify that the hashed location falls within a pre-defined set of permitted cells (the geofence).
• This allows the verifier to confirm "location is within area X" without learning "location is at coordinates (Y, Z)".

The final ZK proof is submitted to a smart contract on a blockchain (e.g., Ethereum, Solana). The contract's verification function:

• Checks the cryptographic proof against a public verification key.
• Validates that the proof corresponds to the correct geofence and time window.
• Upon successful verification, it updates the user's state (e.g., minting an NFT, granting access, recording attendance) in a trust-minimized way. This makes location-based logic programmable and composable.

A critical challenge is preventing users from sharing proofs or using multiple devices to fake presence. SPoP systems implement mechanisms like:

• Device-Bound Attestations: Linking the proof to a unique, non-transferable hardware key.
• Temporal Uniqueness: Enforcing one valid proof per user per specific time interval.
• Proof of Unique Humanity: Optional integration with proof-of-personhood protocols (e.g., World ID) to bind location to a unique human, not just a device. These layers work together to ensure one physical presence equals one valid claim.

SPoP enables a new class of decentralized applications (dApps):

• Physical NFTs & Digital Collectibles: Minting NFTs tied to a real-world location or event.
• Decentralized Physical Infrastructure Networks (DePIN): Verifying that a hardware node (e.g., a wireless hotspot) is deployed in its claimed location.
• Location-Based Access Control: Gating access to online content, DAO meetings, or airdrops based on verified geographic presence.
• Supply Chain Provenance: Creating an immutable, location-stamped record of an asset's journey.

A Spatial Proof-of-Presence is generated by a user's mobile device, which cryptographically signs a message containing a geographic coordinate and a timestamp. This signed proof is submitted to a smart contract or oracle network for verification, creating an immutable, trust-minimized record of physical location. The system relies on device-level security (like Secure Enclaves) to prevent spoofing.

• Key Inputs: GPS coordinates, timestamp, device signature.
• Verification: On-chain contract checks cryptographic signatures and logic (e.g., geofence boundaries).
• Output: A non-fungible token (NFT) or verifiable credential attesting to the presence event.

SPoP enables a new class of location-dependent decentralized applications (dApps). Key applications include:

• Geofenced Airdrops & Rewards: Distributing tokens or NFTs only to users who visit a specific physical location, such as a store, concert, or landmark.
• Proof-of-Attendance Protocols (POAP): Issuing verifiable digital badges for real-world event attendance.
• Location-Based Gaming & NFTs: Creating gameplay mechanics or NFT minting events triggered by physical movement and exploration.
• Supply Chain & Logistics: Providing cryptographic proof of a goods' presence at checkpoints without revealing the entire route.

Building a SPoP system involves a stack of complementary technologies:

• Client-Side SDKs: Libraries (e.g., for iOS/Android) that handle secure location signing on the user's device.
• Verification Oracles: Decentralized oracle networks like Chainlink or API3 that fetch and verify location data off-chain before settling on-chain.
• Geospatial Smart Contracts: Contracts containing the business logic for geofencing, proof validation, and reward distribution.
• Privacy Layers: Optional zero-knowledge proof systems (e.g., zk-SNARKs) to prove location within a zone without revealing the exact coordinates.

Implementing SPoP introduces unique challenges around location spoofing and user privacy.

• Spoofing Resistance: Relies on trusted execution environments (TEEs), hardware security modules, or consensus among multiple independent location sources (e.g., GPS, WiFi, Bluetooth beacons).
• Privacy Risks: Naive implementations leak sensitive, persistent location data directly onto a public blockchain.
• Mitigation Strategies: Use of zero-knowledge proofs to validate location predicates (e.g., 'is in New York') without revealing coordinates, or storing only hashed proofs on-chain with detailed data held off-chain.

Often used interchangeably, Proof-of-Location (PoL) is a broader category that includes Spatial Proof-of-Presence. Key distinctions:

• Spatial Proof-of-Presence: A specific, user-generated claim about being at a point at a moment in time. It's a cryptographic assertion.
• Proof-of-Location: Can also refer to systems or consensus protocols (like FOAM's validator network) that establish a shared truth about a location without a single user's claim.
• Analogy: SPoP is a 'signed statement,' while PoL can be the 'notary public' or 'consensus mechanism' that certifies location data more broadly.