Layer-1 blockchain Aptos has launched an optional Encrypted Mempool feature designed to shield traders from maximal extractable value (MEV) attacks, including frontrunning and sandwich attacks. The feature went live on Aptos mainnet on Monday and allows users to opt in to keep pending transactions encrypted until their block ordering is finalized.
The feature targets institutions submitting large transactions, traders seeking to avoid MEV risk, AI agents, and builders. Aptos noted that on major blockchain networks today, transaction details are visible to anyone monitoring the network before execution, enabling bots to trade against users or replicate their strategies.
Scale of MEV Attacks
Sandwich attacks have imposed significant costs on traders across major networks. Ethereum traders lost approximately $60 million to sandwich attacks over a 12-month period through October 2025, according to analysis of EigenPhi data. On Solana, sandwich attacks generated $29.7 million for bots over an 11-month period, affecting approximately 2.2 million wallets across nearly 6.9 million identified attacks.
How the System Works
When users opt in, a compatible wallet or application encrypts transaction contents on the user's device before sending it to Aptos. Transaction details such as assets and amounts remain hidden, while the sender's address and gas fee remain visible.
Encrypted transactions enter the mempool, where pending transactions await inclusion in a block. Validators agree on transaction order while remaining blind to the contents. Once ordering is finalized, validators collectively decrypt the transactions, which are then executed and recorded onchain. No single validator can decrypt a pending transaction independently.
By keeping transaction details hidden until ordering is fixed, the system prevents bots from reading pending orders and inserting trades ahead of or around them to profit at users' expense.
Trade-offs and Costs
The protection mechanism comes with added expenses and modest delays. Encrypted transactions carry a minimum gas price at twice the network's base minimum fee. Testing involving 50 nodes showed the system adds approximately 20 milliseconds per block compared to the existing consensus implementation.
Competitive Landscape
Aptos joins other networks offering MEV protection mechanisms. Gnosis Chain launched an encrypted mempool using Shutter in July 2024, while Ethereum's Flashbots Protect routes transactions privately to block builders. Aptos distinguishes its approach by having existing validators handle both transaction ordering and decryption, rather than relying on a separate decryption committee or trusted builders.
