zipcoin Source

How it works

Couriers

The staked layer between you and the chain, and the cover traffic that keeps the pool moving.

A stronger decentralized layer in the middle between users and a chain, that is not itself a chain.

Vitalik Buterin, The cryptographic world computer

The couriers are that layer for zipcoin. In the novel, people pay others to rebroadcast their messages anonymously. Here, couriers carry your sealed proofs to the chain.

A sealed proof travels from a person to a courier, waits there a while, and goes on to the chain at a random moment. a courier youthe chain
  • Spends that never touch your wallet

    When you spend, couriers submit for you, so the spend never touches a wallet that could identify you. They stake ZC to do the job.

  • Timing that says nothing

    A courier can hold a proof and send it at a random moment. It signs a receipt for the job, and if it doesn't deliver when it could have, anyone can slash its stake.

  • Nothing taken on trust

    Couriers serve the pool's state, and anyone can check it against the chain's own records, so no courier has to be believed.

  • They can't change your job

    A courier can delay or refuse a job, but never change it: your proof fixes the recipient, the amounts, the message and the courier's own fee.

The pool is never quiet

Couriers keep the pool moving. At random moments they zip coins in, pass notes back into the pool and take some out, a part of a note at a time, the way people pay. Your deposit and your spend stop lining up.

  • Each courier keeps some ZC zipped. At random moments it zips fresh coins in, rezips part of a note back into the pool, or unzips part and zips it back later.
  • Its moves are ordinary sizes: a few dozen coins in, or part of a note out, like someone splitting a payment.
  • A daily gas budget caps it, and it never trades or touches the market. Pool actions only.
  • So the pool always has background activity. A real deposit followed by a real spend no longer stands out in time, and every rezip looks like anyone else's.
  • Veridia's residents add everyday traffic of their own: they keep their savings in the same pool and send through the same couriers. More on Veridia.

The honest limit: a courier's own deposits come from its known wallet, so the strongest cover is its rezips and the timing noise.

A timeline of the pool: couriers' zips, rezips and unzips fall at random moments, and one person's deposit and later spend sit among them without standing out. zip inrezipunzipyou zipyou spend time