Linea Proof-of-Humanity API

Linea Proof-of-Humanity API

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Project Context

Sybil attacks represent one of Web3’s major challenges: how do you ensure that an address corresponds to a unique human and not a bot or multiple accounts controlled by the same person?

Linea Proof-of-Humanity (PoH) is an infrastructure for verifying that an Ethereum address belongs to a verified human user while preserving their privacy. The system relies on the Verax attestation protocol and offers onchain integration via EIP-712 signatures.

System Architecture

The PoH infrastructure consists of two main APIs:

PoH API: Off-chain Verification

The verification API aggregates Verax attestations to determine an address’s PoH status.

Tier System

PoH status is calculated using a tiered system:

  • Tier 1 (High Trust): KYC-like verification

  • Tier 2 (Moderate Trust): Social/reputation attestations

To be considered "PoH verified", an address must have:

  • 1 Tier 1 attestation, AND

  • 1 Tier 2 attestation

Main Endpoints

GET /poh/:address     # v1 verification (multi-issuer)
GET /poh/v2/:address  # v2 verification (Sumsub only)
POST /poh/batch       # Batch verification

Flagging System

A database of suspicious addresses is maintained to ensure the system’s integrity. It is based on community reports and deeper analyses provided notably by Nansen.

PoH Signer API: Bridge to onchain

This API generates EIP-712 signatures enabling smart contracts to verify PoH status.

Signing Flow

  1. User requests a signature for their address

  2. API verifies PoH status via the PoH API

  3. If verified, an EIP-712 signature is generated

  4. The signature can be submitted to any smart contract

Signature Security

  • Web3Signer: private key securely stored

  • Domain binding: signature bound to contract and chainId

onchain Integration

Smart contracts can verify PoH status in a trustless manner.

Use Cases

Sybil-Resistant Airdrops

Fair token distribution with a single allocation per verified human.

Weighted Governance

Voting systems where PoH users have higher weight or where only verified humans can vote.

DeFi with Controlled Access

  • Higher LTV for PoH borrowers

  • Reduced fees for verified users

  • Priority access to new features

Gaming and Competitions

Multi-accounting prevention in tournaments with rewards.

Technical Details

Backend Architecture

  • NestJS: enterprise API framework

  • TypeScript: strict typing

  • Axios: HTTP client for inter-service communication

  • Winston: structured logging

  • Prometheus: observability metrics

Resources

Note
 Linea PoH represents a cornerstone of Linea’s identity infrastructure, enabling the building of Sybil-resistant Web3 applications while respecting user privacy.