Layer-1 blockchain Aptos has introduced an optional new feature designed to shield traders from attacks involving maximal extractable value (MEV), profit captured by exploiting knowledge of pending transactions, including frontrunning and sandwich attacks.

On Monday, Aptos announced in an official statement that its Encrypted Mempool is now live on the network's mainnet, allowing users to opt in and keep pending transactions encrypted until their block ordering is finalized. The company said the feature was built for institutions submitting large transactions to the chain, traders seeking to avoid MEV risk, AI agents, and builders.

“When you send a transaction on any major chain today, anyone watching the network can see the details before it executes, the function you're calling, the assets and amounts involved, and the contracts you're interacting with,” Aptos said. “Bots use that visibility to trade against you or copy your strategy.”

The threat is substantial. Sandwich attacks, a common form of MEV exploitation, cost Ethereum traders approximately $60 million over the 12 months through October 2025, according to Cointelegraph's analysis of EigenPhi data. On Solana, research by Bitquery found that sandwich attacks generated $29.7 million for bots over an 11-month period, with nearly 6.9 million attacks affecting about 2.2 million wallets. Against that backdrop, encrypted or private transaction routing has become an active area of development across major networks.

How Encrypted Mempool Works

When a user opts in, a compatible wallet or application encrypts the transaction's contents on their device before sending it to Aptos. Details such as the assets and amounts involved remain hidden, while the sender's address and gas fee stay visible.

The encrypted transaction then enters the mempool, where pending transactions wait to be included in a block. Validators agree on the order of transactions while remaining blind to their contents. Once the ordering is finalized, validators collectively decrypt the transactions, which are then executed and recorded onchain. No single validator can decrypt a pending transaction on its own.

Keeping transaction details concealed until their ordering is fixed can prevent bots from reading pending orders and inserting trades ahead of or around them to profit at users' expense.

The protection comes with added costs and a small delay. Encrypted transactions carry a minimum gas price set at twice the network's base minimum, according to Aptos' developer documentation. The company also said the system adds roughly 20 milliseconds per block in tests involving 50 nodes, compared with the existing consensus implementation.

Aptos joins a group of networks offering protection against harmful MEV. Gnosis Chain launched an encrypted mempool using Shutter in July 2024, while Ethereum's Flashbots Protect routes transactions privately to block builders. Aptos said its distinguishing feature is that its existing validators handle both transaction ordering and decryption, rather than relying on a separate decryption committee or trusted builders. How far the protection reaches in practice will depend on wallet and application integration, since encryption must be applied on the sender's device before a transaction is submitted. Transactions sent without that support remain visible to network observers, the same exposure Aptos described on major chains today.