Aptos Unveils Encrypted Mempool to Thwart Sandwich Attacks

The optional feature hides transaction details until orders are finalized, preventing bots from exploiting pending trades.

The optional feature hides transaction details until the order is finalized and prevents bots from abusing pending transactions.

Layer 1 of the Aptos blockchain has launched a new optional feature that can help protect traders against attacks involving maximum minable value (MEV), including forward and sandwich attacks.

On Monday, Aptos said its encrypted Mempool feature is now live on its mainnet, allowing users to choose to encrypt pending transactions until their block order is finalized. Aptos said the feature was built for institutions sending large transactions to the chain, traders who want to avoid MEV risk, AI agents and creators.

"When you send a transaction on any main chain today, anyone watching the network can see the details before it's executed, the function you're calling, the assets and amounts involved, and the contracts you're interacting with," Aptos said. Bots use this insight to trade against you or copy your strategy.

Sandwich attacks, a type of MEV attack, cost Ethereum traders about $60 million in the 12 months to October 2025, according to Cointelegraph's analysis of EigenPhi data. At Solana, sandwich attacks generated $29.7 million for bots over an 11-month period analyzed by Bitquery, which identified nearly 6.9 million attacks that affected about 2.2 million wallets.

When a user participates, a compatible wallet or app encrypts the contents of the transaction on their device before sending it to Aptos. Details such as assets and amounts involved remain hidden, while sender addresses and gas charges are visible.

The encrypted transaction enters the mempool, where pending transactions wait to be placed in a block. Creditors agree on the order of transactions while being indifferent to their contents.

Once the order is finalized, the validators collectively decrypt the transactions, which are then executed and recorded on the chain. No validator alone can decrypt a pending transaction.

Keeping transaction details hidden until their orders are confirmed can prevent bots from reading pending orders and inserting trades in front of or around them to profit at the expense of users.

Protection comes with additional costs and small delays. According to Aptos developer documentation, encrypted transactions have a minimum gas price of twice the network's base minimum. Aptos also said the system adds about 20 milliseconds per block in tests involving 50 nodes compared to existing consensus implementations.

Aptos joins other networks that protect against harmful MEV. Gnosis Chain launched an encrypted wallet in July 2024 using Shutter, while Ethereum Protect's Flashbots route transactions privately to block creators. Aptos said that what sets it apart is that its existing validators perform both transaction ordering and decryption, rather than relying on separate decryption committees or trust builders.