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Starknet’s privacy pool holds funds in a shielded balance, so amounts and balances stay off the public ledger. avnu’s paymaster lets users interact with that pool without compromising their privacy: actions are proven client-side with zk-proofs, and the relayer submits the transaction on-chain, so you never expose a public account to pay gas and link yourself back to your private balance.
Preview. Private transactions rely on @avnu/avnu-sdk >= 4.2.0-next.2 (privacy service) and a proving backend — the Starknet privacy SDK or a STRK20-capable wallet. The API surface may still change. Questions? Reach out on Telegram.

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How it works

A private transaction never moves tokens from a public account. Instead, it goes through three steps:
  1. Private balance. Tokens you deposit into the privacy pool are held as shielded notes, so balances and amounts stay off the public ledger.
  2. Proof. Each action (withdraw, transfer, swap) becomes a proof built client-side — by the privacy SDK or by a STRK20-capable wallet — against a recent provingBlockId.
  3. Execution. The paymaster bundles the proof into a single on-chain transaction through its forwarder contract, and can pay the gas on your behalf.

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Fees

Every private transaction carries two costs: the gas fee that goes to the network, and the pool fee that goes to the privacy pool. Private transactions run in the sponsored_private fee mode: the relayer pays the gas, and the user pays only the pool fee — from their private balance, in the token of their choice (poolFeeToken), converted from the base STRK amount by the paymaster’s price oracle. Sponsoring requires a paymaster API key from the Portal, the same setup as gasfree.

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Transaction types

TypeWhenExample
apply_actionNo user call neededWithdraw, private swap
invoke_and_apply_actionA user call is required (such as an approve), wrapped in execute_from_outside and signed by the userDeposit

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Prerequisites

Before you start, make sure you have:
  • @avnu/avnu-sdk >= 4.2.0-next.2, which ships the privacy service: executePrivateSwap, buildPrivateSwapFee, submitPrivateSwap (the paymaster client is built in, targeting starknet.paymaster.avnu.fi by default — override with AvnuOptions.paymasterBaseUrl, e.g. sepolia.paymaster.avnu.fi for testing)
  • a proving backend: the Starknet privacy SDK, or a STRK20-capable wallet (starknet.js >= 10.4, WalletAccountV6)
  • a funded private balance for the token you want to sell, so deposit into the pool first

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Next steps

Private Swap via avnu

Execute a sponsored, gasless private swap step by step