Encrypted Mempool Goes Live on Aptos So Bots Can’t Read Your Receipts Mid-Sandwich 🥪

Aptos has rolled out an opt-in Encrypted Mempool feature on its mainnet designed to shield users from frontrunning and other maximal extractable value (MEV) attacks by keeping pending transaction contents hidden until block ordering is finalized. The Layer-1 network announced the launch on Monday, positioning the tool for institutions placing large trades, retail traders seeking to reduce MEV exposure, AI agents and developers. Sandwich attacks, a common MEV strategy, cost Ethereum traders approximately $60 million over the 12 months through October 2025, according to Cointelegraph’s analysis of EigenPhi data, while on Solana sandwich attacks generated $29.7 million for bots across an 11-month period examined by Bitquery, which counted almost 6.9 million attacks affecting roughly 2.2 million wallets.

Under the new design, a user’s wallet or compatible application encrypts the transaction payload on-device before broadcasting it to the network. The sender’s address and gas fee remain visible, but the function being called, the assets involved and the amounts stay concealed while the transaction waits for inclusion in a block. Validators then agree on the ordering of the encrypted transactions without seeing their contents, and once ordering is fixed they collectively decrypt and execute the batch onchain. No single validator can decrypt a pending transaction alone, Aptos said, describing the approach as an alternative to relying on a separate set of trusted decrypters or a private transaction router.

The privacy guarantee carries tradeoffs. Encrypted transactions carry a minimum gas price at twice Aptos’ base network minimum, according to the project’s developer documentation, and Aptos said its testing showed the system adds roughly 20 milliseconds per block on a 50-node test network compared with its existing consensus implementation. Aptos framed the feature as a defense against bots that watch pending orders to insert trades ahead of or around users, a category that includes the sandwich strategy, in which attackers place orders before and after a victim’s trade to capture price impact.

Aptos joins a small group of networks offering built-in or third-party MEV mitigation. Gnosis Chain launched an encrypted mempool built on Shutter in July 2024, and Ethereum traders can route transactions privately through Flashbots Protect. Aptos said its design differs in that the network’s existing validators handle both ordering and decryption, rather than offloading that role to a dedicated committee or a trusted block builder. The Aptos Foundation separately pledged $50 million to support infrastructure for AI agents building on the chain.

The feature lands as on-chain MEV losses continue to draw industry attention, with researchers tracking tens of millions of dollars in annualized sandwich attack profits across major chains. Aptos has not disclosed how many wallets or applications have enabled the new mempool since launch, and the project did not immediately respond to questions about adoption metrics.