Questions, answered plainly.

What is a stamp?#

The postage for one operation of a fresh address. A prepaid stamp is bought in a booklet, in ETH, from any wallet; the relay signs it blind, so it cannot later tell which purchase it came from. A mined stamp is free: your device solves a small proof of work bound to the operation. Either way the Stamp paymaster pays the gas, and the fresh address never holds ETH.

Who pays for the gas?#

For a prepaid stamp, you do, in advance: the stamp's gas share sits in the paymaster's EntryPoint deposit as the stamp float until a stamp spends it. For a mined stamp, the free lane does: a small budget per 15-minute epoch, topped up from the paymaster's treasury, which the $STAMP creator fees refill. A failed op never costs you ETH.

How much does a stamp cost?#

The relay's gas quote for the heaviest operation a stamp can pay for, times a safety factor of 1.5, plus a 25% markup. The PostOffice keeps the price inside owner bounds and lets the relay move it by at most ±50% per 10 minutes. The current price is on Live parameters.

Can I get a refund?#

No. Stamps pay gas only, are never refunded and never carry value. An unused stamp expires 120 days after its 30-day issuing window closes.

Is this a mixer?#

No. The paymaster pays gas for one UserOperation at a time. It never holds, pools or moves your tokens, and it doesn't hide where tokens came from: assets move exactly as they would with ETH for gas, in public. It removes one specific link, the ETH top-up a fresh address would otherwise need.

What does the relay learn?#

At purchase: your wallet, how many stamps, the blinded messages and your IP address. At use: the fresh address, the operation, the stamp and your IP address. Blind signing keeps it from pairing the two by the stamp itself. Your IP address and your timing can still pair them: wait before using fresh stamps, buy several at once, and use Tor or a VPN.

What stays visible to everyone?#

Your purchase (the PostOffice records who bought how many), whatever the fresh address receives (the sender is linked to it, publicly and permanently), and every operation it makes. See the privacy guide.

What if I lose my stamps?#

They are gone. Export your stamps (encrypted with a passphrase) and keep the file: lost stamps cannot be reissued, because nobody, the relay included, knows which serials were yours.

Can someone steal my stamps?#

A stamp is a bearer token: whoever holds its serial and signature can spend it, so guard your stamps like cash. Nothing spendable ever appears on chain: an op shows only the stamp's nullifier, a hash of its serial.

Can a stamp be used twice?#

The relay refuses a stamp that is in flight or already cancelled, and the paymaster records every stamp's nullifier on chain. A double spend that got through anyway would be public, with its first use, for anyone to see.

How long do stamps last?#

Stamps are issued in 30-day windows and stay valid 120 days after their window closes. The issuer's keys and window policy are published, and the SDK refuses any other, so the relay cannot hand out stamps that single you out.

Where does the money go?#

The gas share of a stamp pays for gas. The markup goes to the DeadLetterOffice, which buys $STAMP on its own market and sends it to 0x…dEaD (Pons tokens have no burn()). The $STAMP creator fees, collected by anyone through the CreatorFeeSink, fund the free stamps.

Will mining cook my CPU?#

Mining runs in Web Workers at the thread count you pick (Gentle uses one core), stops at the eighth valid hash and never runs in the background. A typical op takes seconds on a laptop. You can stop it at any time; nothing is sent until the proof is done. A prepaid stamp needs no mining at all.

Why did mining take longer than expected?#

Every hash has the same odds, so mining has no memory: being unlucky for a while doesn't make the next hash likelier. With 8 sub-solutions the 95th percentile is about 1.64 × the average. Past three times the average, something else is wrong: try more threads, or wait for the next epoch if difficulty just rose.

Why "waiting for the next epoch"?#

Before sending, the SDK checks that the op can reach the relay before it stops accepting the current epoch, and that the deposit (and, for a mined stamp, the epoch's free budget) has room for it. If not, it waits for the next roll (epochs last 15 minutes) instead of wasting your work or your stamp.

Can a GPU farm drain it?#

It can use up an epoch's free budget quickly: proof of work is a rate limiter, not economic security. The budget bounds the loss (one top-up per epoch and an immutable daily cap), and honest users wait for the next epoch. Prepaid stamps never draw on that budget: their gas was paid in advance.

Why EIP-7702 and not a smart-contract wallet?#

A 7702-delegated EOA keeps the same address as the key, needs no deployment transaction, and the bundler applies the delegation in its own type-4 transaction. The paymaster checks on-chain that the sender uses Simple7702Account v0.9, so every account behaves the same.

Which bundler can I use?#

Only the relay's. Co-signed ops are bundled by the relay's own bundler so the deposit ledger stays exact; see Run your own relay.

Do I need an API key?#

No. The relay URL is the only setting. The relay rate-limits reads and issuance per client network in memory; sends are protected by the stamp or the proof itself.

Is it on mainnet?#

Stamp goes straight to Robinhood Chain mainnet (chain 4663), with no testnet step; a local fork (31337) is for development only. The StampPaymaster is 0x0AE674eA03A1F174EB09E2ac5fc913bC6b4130eF; every address is on the contract reference. Stamp is an independent project and is not affiliated with Robinhood Markets, Inc.