Fees

How does the protocol decide on the fee?

Currently there are 28 slots in a rollup (we can increase this up to 128), the base fee is calculated as (1/28 of the proof verification gas costs + tx_type_feeConstant) * the gas price at the last rollup * a buffer of 1.2. The tx type fee constant is calculated as the fixed cost of calldata plus a constant depending on the assetId and the transacton type (shield, send, unshiled). For base fees Aztec guarantees a rollup goes on chain every 6 hours currently.

The rollup provider will automatically create a rollup proof whenever it has sufficient fees to cover an L1 transaction, or when the 6 hour block time has elapsed. The last fee slot is the cost for paying for 28 slots in the rollup, and will trigger the rollup to create a proof instantly. The in-between fees levels are equivalent to paying for 10% and 50% of the slots in the rollup, and reduce the 6 hour block time by 10% and 50% respectively. The idea here is to try and encourage users to pay a bit more so we can bring the block time down for everyone once we reach sustained throughput at say 4h.

One small side note, the rollup provider receives a refund for the gas cost of the L1 transaction, any surplus fees are owned by a contract and used to offset future rollups that may not be full.

We wanted to try and encourage a fee market and create a flow where Aztec does not make money from the fees, instead if a user over pays, that payment helps to subsidise future transactions. As more rollup providers come online we will be changing this.

What are the fees for a private transaction on zk.money?

Slow : ? zkETH | ~4 hours

Average : ? zkETH | ~3 hours

Fast : ? zkETH | ~2 hours

Instant : ? zkETH | ~5 minutes

How much do transactions cost?

• Deposit: 51,000 gas

• Internal send: 17,000 gas

• Withdraw: 5,000 gas for ETH to EOA 30,000 gas to contract.

Our new UltraPlonk research will reduce the costs of internal sends by 3x, which we plan to deploy by August 2021.

Do I pay any fees to Aztec for my zkETH/DAI transactions?

Aztec doesn’t make any money from transaction fees on the platform, surplus transaction fees accumulate on a smart contract and are used to subsided future transactions in busy periods with high gas prices.