Aptos Blockchain Introduces Encrypted Mempool to Combat MEV Attacks
Layer-1 blockchain Aptos has rolled out a new optional feature designed to shield traders from maximal extractable value (MEV) exploits, such as frontrunning and sandwich attacks.
The Encrypted Mempool, now live on Aptos’ mainnet, allows users to opt-in to encrypt pending transaction details until their order within a block is finalized. Aptos stated the feature is particularly beneficial for institutions handling large transactions, traders seeking to mitigate MEV risks, and AI agents and builders.
“On any major blockchain today, anyone monitoring the network can see transaction details before they are executed – the function being called, the assets and amounts involved, and the contracts being interacted with,” Aptos explained. “Bots leverage this visibility to trade against you or replicate your strategies.”
MEV attacks, including sandwich attacks, have proven costly. Cointelegraph’s analysis of EigenPhi data indicated that Ethereum traders lost approximately $60 million to sandwich attacks in the 12 months leading up to October 2025. On Solana, a Bitquery examination of an 11-month period revealed that sandwich attacks generated $29.7 million for bots, with nearly 6.9 million such attacks impacting around 2.2 million wallets.
When a user enables the Encrypted Mempool, a compatible wallet or application encrypts the transaction’s contents on their device before submitting it to Aptos. While sensitive details like assets and amounts remain hidden, the sender’s address and gas fee are still visible.
The encrypted transaction then enters the mempool, a holding area for pending transactions awaiting inclusion in a block. Validators determine the order of these transactions without access to their contents.
Once the transaction order is confirmed, validators collectively decrypt the transactions, which are then executed and recorded on the blockchain. Crucially, no single validator possesses the ability to decrypt a pending transaction independently.
By concealing transaction details until their order is set, the feature aims to prevent bots from observing pending orders and inserting their own trades ahead of or around them to profit at the expense of users.
This enhanced security comes with additional costs and a minor delay. According to Aptos’ developer documentation, encrypted transactions incur a minimum gas price double the network’s base minimum. In tests involving 50 nodes, Aptos reported that the system added approximately 20 milliseconds per block compared to the existing consensus implementation.
Aptos joins a growing number of networks offering protection against malicious MEV. Gnosis Chain launched its own encrypted mempool using Shutter in July 2024, and Ethereum’s Flashbots Protect routes transactions privately to block builders. Aptos differentiates itself by having its existing validators manage both transaction ordering and decryption, rather than relying on a separate decryption committee or trusted builders.
