x402 · private payTo

Private x402 payments for AI agents.

xSHADE gives every x402 payment its own one-time address. Agents pay the way they already do. Nobody can add up what your API earns, and your server never holds a key that can spend it.

Add it to your API Make an xSHADE Key

protocol: x402 v2
settles in: USDC, EIP-3009
server holds: public key only

Live x402 call

runs in this tab

The API's xSHADE Keypublic

…

→ GET /v1/weather
← 402 Payment Required
    payTo  … new
    price  0.01 USDC
→ PAYMENT-SIGNATURE (signed USDC)
← 200 OK

Each press is one paid call. Same key, a new payTo.

0 paid calls0 payTo0 spend keys on server

Network

live

network: Sepolia
chain id: 11155111
block: …
shielded addresses: …
contract: 0xE6273F…7Dd619

One paid call, four steps

A normal x402 payment, except the address changes every time and the spend key never touches your server.

01agentCalls your APIAny x402 client. No SDK, no plugin, nothing new to learn.
02your serverAnswers 402 with a new payToMade from your public xSHADE Key. A different address for every call.
03facilitatorSettles the USDCThe agent signs, the facilitator settles, your API returns the data.
04you, offlineScan and sweepYour xSHADE Secret finds every payment. USDC moves out with no ETH needed.Scan in the browser

Add it to your API

One hook on your x402 server. xshade-x402 swaps your fixed payTo for a new shielded address and publishes the scan data in batches.

Seller · your API

import { Announcer, shieldedPayTo } from 'xshade-x402' const announcer = new Announcer({ contract, wallet, publicClient })const shield = shieldedPayTo({  xshadeKey: process.env.XSHADE_KEY, // public key only  onPaid: announcer.add,}) server.onAfterSettle(shield.onAfterSettle) app.use(paymentMiddleware({  'GET /v1/weather': {    accepts: { scheme: 'exact', network, price: '$0.01',               payTo: shield.payTo },   // new address per call  },}, server))

Buyer · any agent

import { wrapFetchWithPaymentFromConfig } from '@x402/fetch'import { ExactEvmScheme } from '@x402/evm' // A plain x402 client. It does not know xSHADE exists.const pay = wrapFetchWithPaymentFromConfig(fetch, {  schemes: [{ network, client: new ExactEvmScheme(account) }],}) const res = await pay('https://your-api.com/v1/weather')

Nothing changes for the buyer. It sees a normal 402 with a payTo, pays it, and gets the data.

Public, on chain

Your xSHADE Keyshareable
Each payment and its payTovisible, unlinked
Ephemeral point E, tagbatched, delayed

Never on your server

xSHADE Secretstays offline
Which payTo addresses are yoursfound by scanning
Spend keysbuilt when you sweep

Public reputation, private income

List your agent in ERC-8004 with an xSHADE Key instead of a fixed wallet. Each payment returns a signed receipt, so buyers can leave reviews that prove they paid without showing where the money went.

In the receipt

agentIdwhich agent was paid
reviewerthe one address that may use it
receiptIdrandom, so it counts once
issuedDaythe day, not the second

Signed with EIP-712 by the receipt signer named in the agent's ERC-8004 profile.

Left out on purpose

payTo addressnot included
tx hashnot included
amountnot included
exact timenot included

Any of these would let someone match the review to a transfer. Copied, forged and missing receipts are rejected.

Under the hood

No pool, no mixer, no relayer. The payTo is plain elliptic-curve math that your server and your secret both compute.

The math, all of it

serverS = e · Kone-time key e per call, your public xSHADE Key K
youS = k · Eyour secret k, the announced point E = e · G
bothh = keccak256(S)first 2 bytes of S become the scan tag
bothP = K + h · GpayTo is addr(P)
youp = k + h mod nthe spend key only you can build

Curve secp256k1. Source: xshade-x402/src/keys.ts and XShade-Main.sol.

On chain now

Sepolia

Shielded addresses announced…

No announcements yet. The first private payment on this contract shows up here.

This is everything the contract stores: an ephemeral point and a 2-byte tag. No receiver.

Or pay a person by hand

The same shielded addresses work without an API. Send ETH or any token to someone's xSHADE Key from this app.