What happens when a server answers 402
Only the first step ever touches your wallet.
01
Deposit once
USDC goes into the pool as a note only your key can open.
Public: your deposit02
Get a price
An x402 endpoint answers with the amount and who to pay.
Nothing on chain03
Prove and withdraw
A proof moves exactly the price to a brand new wallet. A relayer submits it.
Public: pool to a stranger04
Pay with stock x402
The new wallet pays. The facilitator covers the network fee.
Public: a stranger paid05
Sweep
The empty account closes and its rent goes back.
Public: account closedWhat an observer can piece together
Three payments to three merchants. Plain x402 ties them to one address. Through Nocta each comes from a wallet with no history.
Plain x402Linked
…news.site0.05 USDC
…api.dev2.40 USDC
…shop.xyz18.00 USDC
NoctaUnlinkable
…news.site0.05 USDC
…api.dev2.40 USDC
…shop.xyz18.00 USDC
Costs and limits
Detail
Relayer fee0.50 USDC per payment, from your private balance. It covers about 0.0036 SOL of storage the relayer can't recover.
Network feePaid by the merchant's facilitator, as with any x402 payment on Solana.
ProofOne Groth16 proof, 146,835 compute units to verify. Withdrawal and token account fit in one 1,087-byte transaction.
AmountsPublic, as in plain x402. What's hidden is who paid.
TimingA watcher can match the withdrawal to the payment seconds later. Matching either to your wallet is what's hidden.
Anonymity setEveryone who has deposited into the pool.
Two lines on top of your x402 client
Register the private scheme for Solana and wrap fetch. Anything that comes back 402 is paid from the pool.
const scheme = new PrivateSvmScheme({ rpcUrl, keypair, relayer }); const pay = wrapFetchWithPayment(fetch, new x402Client().register("solana:*", scheme)); await pay("https://api.dev/report"); // paid by a stranger await scheme.sweep();