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Experimental — WitnessChain is an early-stage plugin. The interface is defined and the Verify service has experimental server-side verification logic for it; the client plugin (collecting and creating stamps) is still under development on the develop branch. ProofMode is the plugin that’s working end to end today. We’d love to develop this and other proof-of-location plugins with partners — get in touch.

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WitnessChain plugin

WitnessChain provides infrastructure-based proof-of-location through network latency triangulation. Independent challenger nodes measure round-trip times to a prover, then use the speed-of-light constraint to verify the prover’s claimed location. This is fundamentally different from device-based proofs like ProofMode — the evidence comes from the network infrastructure, not the user’s device.

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How it works

  1. A prover registers their claimed location with WitnessChain
  2. Independent challenger nodes send network challenges
  3. Challengers measure round-trip latency and compare against speed-of-light bounds
  4. If the measured latency is consistent with the claimed location, the challenge succeeds
  5. Results include ECDSA-signed attestations from each challenger
This approach provides location evidence that doesn’t depend on the prover’s device being trustworthy — the evidence comes from independent network observers.

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Current status

The plugin is in development on the develop branch. The interface is fully defined: 
class WitnessChainPlugin implements LocationProofPlugin {
  readonly name = 'witnesschain';
  readonly version = '0.1.0';
  readonly runtimes: Runtime[];
  readonly requiredCapabilities: string[];
  readonly description = 'WitnessChain proof-of-location via network latency triangulation';

  collect(options?: CollectOptions): Promise<RawSignals>;
  create(signals: RawSignals): Promise<UnsignedLocationStamp>;
  sign(stamp: UnsignedLocationStamp, signer: StampSigner): Promise<LocationStamp>;
  verify(stamp: LocationStamp): Promise<StampVerificationResult>;
}

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Planned capabilities

MethodDescriptionStatus
collect()Fetch challenge results from WitnessChain APIIn development
create()Parse challenge results into location stampIn development
sign()Sign stamp with prover keyIn development
verify()Verify challenger ECDSA signatures and challenge consistencyIn development

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Challenge result structure

Each WitnessChain challenge produces: 
interface WitnessChainChallengeResult {
  id: string;
  challenger: string;            // Ethereum address of challenger node
  claims: {                      // Prover's claimed location
    latitude: number;
    longitude: number;
    radius: number;
  };
  result: {
    challenge_succeeded: boolean;
    ping_delay: number;          // Measured latency
  };
  message: string;               // JSON-encoded challenge data
  signature: string;             // ECDSA signature from challenger
  consolidated_result: {
    KnowLoc: boolean;            // WitnessChain's location assessment
    KnowLocUncertainty: number;
    verified: boolean;
  };
}

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Why WitnessChain matters for multifactor proofs

WitnessChain provides a fundamentally independent evidence source:
  • Device proofs (ProofMode) rely on the prover’s hardware
  • Infrastructure proofs (WitnessChain) rely on external network observers
When both agree, the independence dimension of the CredibilityVector reflects the corroboration from truly independent systems.