x402f

Trust-minimized, Programmable, Pay-per-use data APIs

x402f extends the x402 protocol to invert the trust model entirely: the server never holds plaintext, never handles payments, and cannot withhold data — even if it goes offline.

Built on Fangorn threshold encryption, x402f enables intent-bound data delivery: content encrypted under publicly verifiable conditions, decrypted locally by the buyer only after payment is confirmed on-chain.

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How It Works

1. Seller registers a datasource and uploads encrypted content via Fangorn — no dedicated infra needed.
2. Buyer receives a ciphertext before payment. They can verify what they're purchasing against chain state.
3. Payment is made via x402. The facilitator verifies it and issues a decryption share.
4. Decryption happens locally. The server never sees plaintext, and can never withhold data post-purchase.

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Key Features

• Programmable pricing — dynamic, verifiable pricing through Fangorn, no code changes required
• Zero seller infrastructure — anyone can sell data without running their own server
• Trust-minimized — buyers start with the ciphertext; payment and ownership are verifiable on-chain
• Censorship-resistant — data cannot be withheld after purchase, even if the server goes offline

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Architecture

x402f consists of two services:

Service	Description	Default Port
Facilitator	Verifies payments and issues decryption shares	30333
Resource Server	Serves encrypted data and coordinates with the facilitator	4021

Both services are stateless and can be run by anyone. See the Fangorn docs to register datasources and upload content.

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Quickstart

Prerequisites

• Node.js 22+
• pnpm

Setup

# Clone and install
git clone https://github.com/fangorn-network/x402f
cd x402f
pnpm install

# Configure environment
cp .env.local .env
# Fill in your details in .env

Run locally

# Start the facilitator (runs on :30333)
pnpm run facilitator

# In a separate terminal, start the resource server (runs on :4021)
pnpm run server

Run with Docker

docker compose up --build

Run the example client

pnpm run client:node

See the full node client example.

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For Data Consumers

• You receive the ciphertext before payment — verify what you're buying before spending anything
• Decryption happens locally after payment — the server cannot withhold your data
• Pricing and ownership are verifiable against finalized chain state

For Data Sellers

• No infrastructure required — the shared resource server handles delivery
• Dynamic pricing — update prices through Fangorn without touching code or redeploying
• Optionally run a dedicated resource server for more control (but you don't have to)

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Environment Variables

Variable	Description
FACILITATOR_DOMAIN	Hostname of the facilitator (e.g. http://facilitator in Docker, or https://facilitator.example.com in prod)
FACILITATOR_PORT	Port the facilitator listens on (default: 30333)

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License

MIT