Public blockchains have a problem most people notice as soon as they use one: your salary, your rent, and your medical payments are visible to anyone with a browser. XPR Network is fast and cheap, but until now it was as transparent as every other public chain.
That changes today. We're launching Private Transactions on XPR Network at private.protonnz.com.
What it is
Private Transactions add confidential transfers to XPR Network — the amounts you send are
hidden, while the parties stay visible on-chain. It's built as a smart contract
(account xprconf), not a private sidechain, so it inherits XPR's zero-fee UX, sub-second
finality, and existing WebAuth wallets.
Under the hood:
- Amounts are hidden by ElGamal commitments and revealed only to holders of the right keys.
- Every transfer carries a Groth16 zero-knowledge proof that the sum balances — no double-spend, no invented value — verified on-chain before the balance moves.
- A mandatory auditor viewing key is committed at the protocol layer. There is no way to send a private transfer that a designated auditor cannot decrypt after the fact.
The last point is deliberate. It's what makes this not a mixer. Compliance, forensics, tax audits, court orders — everything that requires reading a specific transfer's amount — remains possible for the auditor, and only the auditor.
What it looks like
By default your activity is hidden. You see your own balances; nobody else does.
Tap Reveal and your local wallet decrypts the amounts. This is a local action — the chain does not change what it reveals.
Deposits move public XPR into the private pool. Withdrawals move it back out. Both are proven on-chain and cost the same near-zero fee as any XPR transaction.
Activity is visible to you (and your auditor, on request). Amounts everywhere else on the chain remain hidden.
Early access — read this before you deposit
The mainnet contract is live, but we're launching under deliberate limits while we do the last production checks:
- Pool cap: 20,000 XPR total
- Per-deposit cap: 1,000 XPR
- Proving key: the current mainnet uses a rehearsal proving key while we finalise the
multi-party trusted-setup ceremony. Once the ceremony completes, the production key replaces it
via a single
setvktransaction. - Not audited: the smart contract, the circuit, and the client have not been through third-party audit yet. Amounts are small on purpose.
- Testnet is uncapped at testnet.private.protonnz.com — please break it there first.
If you deposit real XPR at this stage, treat it as opting into an early-access product with real technical risk. We'll lift the caps and swap the proving key as soon as the ceremony finalises.
Why a bolt-on, not a private chain?
The original scoping considered launching this as a separate private chain. We chose a smart contract on XPR Network instead because:
- You keep the network you already use. Same accounts, same wallets, same fee model.
- Composability stays real. Public XPR flows in and out of the private pool as public XPR — the rest of the ecosystem doesn't need to know.
- Auditability is enforced by the protocol, not by trust. The viewing key is a required input to the circuit; you cannot produce a valid proof without it.
The technical design (circuit, contract, threat model, key management) lives in
docs/01-design.md in the pulse-privacy repository,
alongside the ceremony tooling and benchmarks.
What's next
- Complete the trusted-setup ceremony and swap in the production proving key.
- Third-party audit of the circuit and the on-chain contract.
- Lift the caps once both of the above are done.
- Port the contract to
pulse-cdt-rustas part of the broader XPR → PulseVM crossover.
Try it on testnet, send a small amount privately on mainnet if you're comfortable with the risks above, and report anything that looks off. This is the biggest single addition to XPR Network's capability set in a long time and we'd rather find any edges now, at small size, than after we lift the caps.
private.protonnz.com — mainnet, early access, capped.
testnet.private.protonnz.com — testnet, uncapped.