Aptos has activated an optional encrypted mempool on its mainnet, hiding transaction payloads until validators finalize their order. The feature is designed to reduce frontrunning and sandwich attacks, in which automated traders exploit visible pending orders by trading before or around them.
Users encrypt a transaction on their device before it reaches the network. The sender address and gas information remain visible, but the function being called, assets and amounts, and contract interactions are concealed while the transaction waits in the mempool. Validators order encrypted transactions without seeing their payloads, then collectively decrypt the transactions after consensus; no individual validator can decrypt a pending transaction alone.
Aptos describes the system as a protocol-level feature that uses the network’s existing validators rather than a separate decryption committee or trusted block builders. Its technical proposal says the system uses batch threshold encryption, with a new encryption key generated for each validator epoch, and is intended to support more than 1,000 transactions per second at launch. The first version protects payload privacy, not full transaction anonymity, and does not hide metadata such as the sender or gas parameters.
The feature is opt-in and requires support from wallets or applications. Existing Move contracts do not need to be changed.
The protection carries a cost. Aptos documentation sets a minimum gas-unit price of 200 octas for encrypted transactions, twice the network base minimum, and says clients or servers enforce that floor. In a 50-node test, Aptos measured about 20 milliseconds of additional latency per block compared with its existing consensus implementation.
The launch places Aptos among networks pursuing protection against harmful MEV through transaction concealment. Aptos’ approach keeps ordering and decryption within the validator system already securing the chain, while leaving users and applications to decide when the added fee and payload-privacy tradeoff is worthwhile.