ETHGlobal Buenos Aires 2025 zkx402 - x402 protocol extension

Archived project

This project has been archived to preserve links from the hackathon. Live project work is over at VHSpace.

Summary

zkx402 is a protocol extension that integrates Zero-Knowledge proofs into x402, enabling verified variable payments and verifiable content metadata.

Consumers (humans or AI agents) gain variable pricing, with eligiblility verified with zkproofs. Producers can prove the providence of their content by attaching zkproofs. e.g. confirmed authorship by a specific journalist, proof of human creation, IoT data with GPS/sensor details.

Use Cases

Being a protocol extension, it's a primitive that has many use cases.

The use case we are most excited about is for making private data commercializable. Data owners would set a high price for data they are OK to lose control of. However, also make it available at a discount for a verified organisation who they are confident will not abuse the data, such as LLM model creators focused on creating transparent models.

There is also impact use cases, where a deep-cover journalist sell sensitive primary content extremely high for the open market but offers standard rates to employers/partners, who also need to cryptographically confirm the content's authentic origin. Whistleblowers can get paid without compromising their safety or Journalist-controlled AI agents can pay for verified private sensitive data. It's like SecureDrop + ZK provenance + dynamic pricing + AI agent economy in one protocol.

Then more future looking, is making content purchasable by an growing automomous AI ecosystem who may perform their tasks better if it had unique verified primary source data.

High-level abstract & value proposition

Consumers (Journalists & AI Agents)

• Variable pricing based on verified identity (50% discount for verified parties)
• Eligibility proven via zkproofs, no trusted third party needed
  • Human journalists → Self.xyz, Worldcoin, zkPassport, or vLayer org proofs (NY Times, The Economist, etc.)
  • AI agents get the proof of humanity from the human to be eligible for the discounted price
  • Unverified → pay full price ($0.01 instead of $0.005)

Producers (Whistleblowers)

• ZK-verified metadata & content provenance (vlayer ZK Email / zkTLS)
• Prove insider status, document authenticity, creation timestamp without revealing identity
• Optional partial identity reveal (e.g. date of birth + country via Self.xyz if journalist already knows who the source is)
• Get paid instantly in USDC on Base while staying fully anonymous

This creates the missing economic layer for truth.

User Flows

Whistleblower Flow

1. Upload sensitive document/photo bundle
2. Generate vLayer ZK proof (ZK Email or zkTLS) → proves insider access + authenticity + creation date
3. Content encrypted + stored on IPFS
4. Listing goes live with "Verified Insider" badge
5. Receive USDC instantly when sold

Journalist (Human) Flow

1. Connect embedded wallet (Coinbase Smart Wallet on Base)
2. Optional: Verify credentials via vLayer (e.g. prove employment at NY Times/The Economist) or Self.xyz
3. Browse leaks → verified journalists see $0.005 price, others $0.01
4. Pay with one click → receive decrypted content + ZK proof bundle

AI Agent Flow (the nuclear demo)

1. Journalist delegates discount via EAS attestation on Base (ERC-8004 pattern)
2. Agent wallet pre-approved $5 budget
3. Agent calls MCP/x402 endpoint → server checks attestation → returns 402 with $0.01 amount
4. Agent pays autonomously → receives content + delivery proof
5. Demo shows agent buying 20+ leaks in 15 seconds while journalist drinks mate

Tech Stack

Frontend app

• Frontend: Vite + React + TypeScript + ShadCN UI + Tailwind CSS + React Router
• UI Components: Radix UI primitives (Dialog, Accordion, Dropdown, etc.)
• Forms: React Hook Form + Zod validation
• Data Fetching: TanStack Query (React Query)
• Charts: Recharts
• Icons: Lucide React

zkx402 payment

• Frontend: Next.js 14 + React + TypeScript
• Wallet & Auth: Coinbase CDP (Embedded Wallet with email/SMS/OAuth login)
• Payments:
  • Client → x402-fetch (HTTP 402 payment client)
  • Server → x402-express + @coinbase/x402 (payment middleware & facilitator)
  • Token → USDC on Base Sepolia
• Backend: Express.js + Node.js + CORS
• APIs: CDP Faucet API + CDP Token Balances API
• Chain: Base Sepolia testnet (chainID: 84532)

Demo Flow

1. Whistleblower uploads "Epstein 2025 Flight Logs.pdf" → vLayer ZK Email proof shows sent from epstein@lol.gov → "Verified Insider" badge appears
2. Verified NY Times journalist connects → sees $0.005 price (vs $0.01 for random wallet)
3. Pays → gets content + proof bundle
4. Same journalist delegates discount to AI agent via one-click EAS attestation
5. Run agent script → autonomously buys every leak under $0.01 in a loop
6. Show transaction history: agent spent $0.37 building the next Pandora Papers overnight

Future Work

How the project can be built further:

• Build MCP server for the leaked contents so that AI agents can consume it

Deployed contract (all verified)

Base Sepolia testnet (chainID: 84532)

| Contract | Contract address | | Self smart contract | | | USDC (testnet) | 0x036CbD53842c5426634e7929541eC2318f3dCF7e | The verified smart contract on Base Sepolia testnet is:

https://sepolia.basescan.org/address/0x036CbD53842c5426634e7929541eC2318f3dCF7e#code

Celo Alfajores testnet (chainID: 44787)

| Contract | Contract address | | Self smart contract | | The verified smart contract for Celo testnet is:

How to run locally

Client

Go to the "client" folder and run these commands after filling in the environment variables based on the example env file:

cd zkx402-demo
npm run install:all
npm run dev:server
npm run dev:client

open client in browser: localhost:3000

Server

For server, go to the "server" folder and run these commands after filling in the environment variables based on the example env file:

cd zkx402-demo
npm run install:all
npm run dev:server
npm run dev:client

open server in terminal

Demo movie

https://youtu.be/kEA0Jhq6qjM

Demo site

https://zkx402.io