ephemeral

Stealth Buy on Uniswap v4

Buy any token on a Uniswap v4 pool straight into an ERC-5564 stealth address, with gas included and an announcement the receiver's wallet can find.

Stealth Buy is a small router for Uniswap v4. It swaps ETH for a token and delivers the token to a one-time stealth address instead of the buyer's wallet. It is the first piece of The Hook: the privacy layer for Uniswap v4.

What one call does

  1. Swaps ETH for the token on the pool you name (exact input). The pool's own hook and fees apply as they would for anyone.
  2. The PoolManager pays the tokens directly to the stealth address.
  3. Sends up to 0.01 ETH along to the same address, so the receiver can move the tokens later without funding that address from a known wallet.
  4. Announces the payment through the canonical ERC-5564 Announcer with the standard token metadata: view tag, 0xa9059cbb, token, amount (57 bytes). Any ERC-5564 wallet that scans, the ephemeral client included, finds it.
  5. Refunds the ETH the pool did not use, and reverts if fewer tokens than your minimum arrive.

Interface

struct Stealth {
    address stealthAddress;  // generated from the receiver's stealth meta-address
    bytes   ephemeralPubKey; // 33-byte compressed key used to generate it
    bytes1  viewTag;         // lets the receiver skip 255 of 256 announcements
    uint256 minOut;          // slippage guard
    uint256 gasTip;          // ETH sent along for gas, at most 0.01 ETH
}

function buy(PoolKey calldata key, Stealth calldata s, bytes calldata hookData)
    external payable returns (uint256 tokensOut);

msg.value is the ETH to swap plus gasTip. The pool's currency0 must be native ETH.

What it hides and what it does not

HiddenWho receives the tokens. The stealth address cannot be linked to the receiver's meta-address or ENS name.
HiddenThat the receiver ever funded that address: the gas is already there.
Not hiddenWho bought. The buyer's address is the sender of the transaction. Buying for yourself from a known wallet links you to the stealth address.
Not hiddenThe amount and the token. They are in the swap and the announcement.

So Stealth Buy protects the receiver: paying someone in a token, gifts, payouts. For yourself it helps only when the ETH comes from a private source.

Design

  • Stateless: no owner, no settings, holds no funds between calls.
  • ETH accounting uses msg.value only, never the contract's balance.
  • Works on any v4 pool with native ETH, with or without a hook.
  • Tested against a pool with a fee-taking hook and a plain pool; an end-to-end test on a local chain buys into a stealth address, finds it with the ephemeral client scan, and withdraws the token and the leftover ETH to a fresh address.

Status

Built and tested. It goes to mainnet after an add-on security review; its address will be listed on Networks.

Stealth vs mixers vs shielded pools

Three ways to get privacy on Ethereum, what each hides, what each costs, and how ephemeral combines with the others.

Build with ERC-5564

What a wallet or app needs to receive and send stealth payments safely, with the pieces you can reuse.

On this page

What one call doesInterfaceWhat it hides and what it does notDesignStatus