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Receiving funds privately ​

Alice, the client, wants to send a salary to her consultant, Bob.

Alice uses MetaMask with Ledger to manage her company's treasury, while Bob, a privacy-savvy crypto professional, uses Curvy to ensure his clients don't get unnecessary insight into his earnings and spending.

Bob has provided Alice with instructions to complete the payment to his ENS: bob.curvy.name, or to simply open https://bob.curvy.name and continue with payment there.

Bob made it clear that he only accepts payment in USDC, but hasn't specified which network to use.

Without asking, Alice sent the funds to Bob's private address on Ethereum, but was reassured by Bob that the system he's using should pick up transfers on Polygon, BSC, Arbitrum, Optimism, Linea, Base, or Gnosis.

Bob uses Curvy, but Alice, the sender, can keep using Ledger + MetaMask without knowing what Curvy is.

Receiving funds privately

Steps explained in detail ​

🔵 Alice ​

  1. Alice enters bob.curvy.name into her wallet of choice. In the background, an ENS resolver powered by the Curvy SDK fetches Bob's public keys from the Identity Registry.
  2. Using the Curvy SDK, a random nonce, and Bob's public keys, a new Portal address is generated to which Bob can receive funds; no contract is deployed at that address yet.
  3. This tuple of information, generated in step two, is what's called an announcement and is stored in a public Announcement Registry.

⚫ Curvy ​

  1. The Curvy Portal Broadcaster continuously syncs announcements from the publicly available API.
  2. After observing a Portal address that has received any of the supported funds, it has the necessary incentive to initiate the deployment of the Portal contract through the Portal Factory. During the deployment, because the address of the portal is deterministically calculated with the anonymous Announcement as input, funds are automatically bridged if needed and shielded inside the Privacy Aggregator.
  3. The Curvy ZK Prover continuously keeps in sync with the Notes emitted by Aggregator.sol, which are indexed in the public Notes Registry.
  4. After a shielding event is observed on Aggregator.sol, the ZK Prover constructs the proof for the shielding of the new note. After successful proof verification on-chain, the new note is emitted, and a new version of the resulting Notes tree is verified using on-chain ZK verifiers that are a part of the Aggregator.sol.

🟢 Bob ​

  1. Some unknown time later, Bob logs into his Curvy App. In the background, immediately upon starting, the Curvy App, using the open-source Curvy SDK, starts syncing the notes from the public Notes Registry, which serves as a fast index of on-chain events emitted by Aggregator.sol.
  2. In Bob's browser, the Curvy SDK simultaneously scans the notes it has synced with his private keys to detect which notes are secretly in his ownership and to decrypt their balances.

IMPORTANT

From the perspective of an on-chain observer, Alice has sent funds to a regular EOA address to which a smart contract (Portal) was later deployed by the Portal Broadcaster. This deployment moved the funds to the Curvy Privacy Protocol (Aggregator.sol), and most importantly, the new owner of these funds (Bob) is completely hidden.