Key concepts
The handful of ideas behind noircash - public NOIR and notes, shares, harvesting, registration and the privacy set.
Public NOIR and private notes
NOIR is an ordinary ERC-20, launched on Pons. NOIR in your wallet is public NOIR: like any token balance, anyone can see it, and wallets, exchanges and aggregators handle it as usual. It earns nothing.
noircash adds a private side, the vault. Two actions move NOIR between the two:
| Action | From | To |
|---|---|---|
| Shield | Public NOIR in your wallet | A new private note in the vault |
| Unshield | Your private notes | Public NOIR at any address |
Privacy is a choice: NOIR bought on another app, an aggregator or the Pons site arrives as public NOIR, and stays public until you shield it. Buying in the noircash app is the exception: it buys and shields in one transaction, so the NOIR lands straight in a note.
Notes
A note is a private piece of value. On-chain, a note is only a commitment: a hash that reveals neither the amount nor the owner. Next to it the chain stores the note's contents encrypted to the owner's viewing key, so the owner's app can find and read it.
Your private balance is the sum of your unspent notes. When you spend, the notes you use are marked as spent with a nullifier: a value that only the owner can compute, and that cannot be linked back to the note. New notes are created for the recipient and for your change.
→ Notes, commitments and nullifiers
Shares, not tokens
A note does not hold a number of tokens. It holds shares of the vault. The vault holds all the NOIR behind all the notes. The value of one share is:
share value = NOIR in the vault / total sharesWhen NOIR is donated to the vault, no shares are added, so each share, and each note, is worth more NOIR. Your private balance grows by itself, without any transaction and without anyone learning how much you hold.
Harvesting: where the yield comes from
Every NOIR trade on Pons, on the bonding curve and later on the Uniswap v4 pool, pays Pons' 1% trade fee, with no creator tax. Pons keeps 30% of that fee. The rest, 0.7% of the trade, goes in ETH to the noircash FeeHarvester, the contract Pons records as NOIR's creator fee recipient.
Anyone can call harvest(). It collects that ETH, first tops up the ETH the vault uses to pay for private
transactions, then buys NOIR with the rest and donates it to the vault. The caller keeps 0.5% of the ETH as a tip,
so nobody has to run it for the system to work.
Only notes earn from this. Public NOIR does not, so the place to hold NOIR is in private.
Keys
You never write down a new seed phrase. Your wallet signs one message, and the app derives from it:
- a viewing key, which finds and decrypts your notes;
- a nullifier key, which proves you own a note inside the proof.
Spending also needs a fresh signature from your wallet for each transaction. So a leaked activation signature reveals your notes but cannot move them.
You register your public keys on the vault once, so that other people can send you private notes.
→ Keys
The privacy set
Privacy comes from blending in. Every note ever created lives in one Merkle tree, and a proof shows that you spend some notes in that tree without saying which ones. The privacy set is the number of notes you hide among: the more people use noircash, the larger it is, and the better everyone is protected.
Early on the set is small, so timing and amounts matter more. Staying private has practical advice.
Introduction
noircash is the private side of NOIR, an ordinary token on Robinhood Chain. Shield NOIR into encrypted notes to send and sell it privately and to earn from every trade.
Whitepaper
The technical paper behind noircash - notes, keys, the spend circuit, the vault, gas abstraction and the security and privacy analysis.