White paper
Why PCASH exists and how it works, in one document.
Learn
PCASH in six ideas
Private money on Ethereum, in short. The white paper makes the full case, and the protocol specification has the exact rules.
Private
When you pay with PCASH, the sender, the recipient, the amount and your balance stay private. Each payment carries a zero-knowledge proof: the network checks that it is valid without learning any of those details.
What can other people see?
That an account registered, that a transaction happened, its fee and timing, and which of the two transaction sizes it used. If you publish a transaction from your own Ethereum address, that address is linked to it. They cannot see the sender, recipient, amount or balance.
There is no public PCASH
PCASH exists only in private form. There is no public token, nothing to deposit and nothing to withdraw.
Shielded pools such as Tornado Cash and Railgun hide assets deposited into them, so everyone's privacy depends on how much capital stays inside. PCASH has no inside and outside. Joining takes one Ethereum transaction and no deposit, and an account holding nothing looks the same as one holding a lot. The crowd you hide in grows with every account, and it does not shrink when people spend.
Is PCASH ETH, or wrapped ETH?
No. PCASH is its own asset. It exists only inside PCASH, and no bridge redeems it for ETH. You do pay Ethereum gas, in ETH, to publish transactions.
Where PCASH comes from
PCASH starts at zero. New PCASH is issued for successful payments, including a payment of zero to yourself, so anyone can mine it by using the network. Total issuance is capped at one billion PCASH, with no premine, allocation or sale.
Each block's issuance is limited and shared equally among the payments that earn it. The amount per payment follows a curve that declines as supply is issued and adjusts to how quickly issuance is running.
How do I get PCASH?
Mine it by making transactions, even a payment of zero PCASH to yourself, or buy it from a holder for ETH in the Marketplace. Neither mining that way nor receiving PCASH needs an account. Spending does, and creating one takes one Ethereum transaction.
Built on Ethereum, with no one in charge
PCASH transactions are published to Ethereum, and every PCASH node derives the same state from Ethereum's history. There is no sequencer, operator, validator set or upgrade key, and anyone can collect transactions and post them. The rules change only if people choose to run new software, the way Ethereum itself changes.
Why isn't PCASH a smart contract?
A privacy contract has to choose. An immutable one cannot fix a bug without moving everyone to a new contract, which breaks their privacy. An upgradeable one is only as safe as whoever controls upgrades. PCASH is defined by rules for reading Ethereum history instead, so each version is immutable, and a new version applies only if people choose to run it.
White paper: The smart-contract dilemmaWhat am I trusting?
Ethereum's consensus and history, the soundness of the zero-knowledge proof system, and the correctness of PCASH's circuits and software. Not a sequencer, an administrator, a bridge, or other users keeping their money in a pool.
White paper: What you trustWhat happens if I lose my Ethereum key?
Your Ethereum key is needed once, to create your account. After that, your account's own rules decide who can spend, and they can use other keys. What never changes is the secret your account needs to spend its notes, fixed when the account is created. No one can restore it, and losing it loses the PCASH. The wallet on this site derives that secret from your Ethereum key, so there is nothing extra to back up, and losing the key loses your PCASH.
White paper: Security assumptions and failure modes
Trade it for ETH without a middleman
A seller locks PCASH in an escrow contract. It releases the PCASH to a buyer who proves an ETH payment to the seller, and returns it to the seller if a deadline passes. No operator holds either side's funds, and the buyer must claim before the deadline. The Marketplace on this site works this way.
Can I turn PCASH back into ETH?
Only by selling it to someone for ETH, through an escrow contract. There is no withdrawal and no bridge.
Build on it
Every account sets its own spending rules: a signature, a passkey, a multisig or a recovery condition. Contract accounts have rules that can never change, which makes escrow, vesting and sales credible. Anyone can create a private fixed-supply asset, and rules can depend on events on Ethereum. What you can build.
White paper: AuthorizationRead further
Protocol specification
The exact rules every implementation follows.
Developers
Building on PCASH, running a node, and the technical reference.