Aptos has activated its optional Encrypted Mempool on mainnet, enabling compatible wallets and applications to conceal pending transaction instructions, assets, and amounts until validators finalize transaction ordering. The feature is designed to counter maximal extractable value (MEV) practices, including frontrunning and sandwich attacks, but it is not free: encrypted transactions carry a minimum gas price twice the network's base minimum, while sender addresses and gas-fee information remain visible.

The network announced the mainnet activation on Monday, October 12, describing the feature as an option for institutions submitting large transactions, traders seeking to limit MEV exposure, AI agents, and builders. Large orders are a natural focus, since the size of a trade is what creates the price movement that frontrunning and sandwich strategies profit from. The activation applies network-wide, but individual transactions are encrypted only when they are submitted through supporting software.

MEV refers to value that can be captured by reordering, inserting, or censoring transactions within a block. On major blockchains today, anyone watching the network can see the details of a pending transaction before it executes: the function being called, the assets and amounts involved, and the contracts being interacted with. Frontrunning exploits that visibility by placing a bot's trade ahead of a pending order, while a sandwich attack surrounds a user's transaction with orders on both sides to profit from the resulting price movement.

Aptos said the feature is designed to prevent bots from reading pending orders and inserting trades ahead of or around them; in its words, “Bots use that visibility to trade against you or copy your strategy.”

Reactions to the announcement appeared on X:

I think we underestimate how much traders lose because transactions are visible before execution. @Aptos finally launched an optional Encrypted Mempool on mainnet. The idea is simple: transactions stay encrypted until validators finalize their order, making it much harder for… pic.twitter.com/8Mit9Cv8Vo
— Rain (@raintures) October 13, 2026

How the Encrypted Mempool Works

A compatible wallet or application encrypts the transaction contents on the user's device before submitting them to Aptos. The transaction then waits in the mempool—the queue of transactions awaiting inclusion in a block—while validators agree on its order without seeing its contents. During this window, the encrypted submission sits in the queue any other transaction, but its contents cannot be read.

Once ordering is finalized, validators collectively decrypt the transaction, which is then executed and recorded onchain. No individual validator can decrypt a pending transaction alone. That shared-decryption requirement is what closes the window in which a single party could otherwise act early on a pending order while ordering is still being decided.

In tests involving 50 nodes, Aptos reported that the process added about 20 milliseconds per block compared with its existing consensus implementation. That is a modest reported delay, but the higher minimum gas price means traders must weigh the added protection against the extra transaction cost. Because the latency figure comes from a 50-node test, performance at full mainnet scale is a practical detail to track as encrypted usage develops.

Protection Without Full Transaction Anonymity

The encrypted payload hides the instructions, assets, amounts, and contract interactions while a transaction is pending. It does not hide the sender's address or gas-fee information, so the feature protects transaction contents rather than making users anonymous. Observers can still see who is sending and what they are paying in gas; what is shielded is the content of the pending instruction. That distinction matters for anyone assessing what the feature can—and cannot—shield.

The design aims to prevent bots from exploiting visible orders through frontrunning or sandwich attacks that profit from price movements around user transactions. Aptos's reported two-times-base-minimum gas price and roughly 20-millisecond per-block test impact are the concrete costs attached to that protection.

The change is a protocol infrastructure update, placing it in the same broad category as work on validator performance and network design, such as Ethereum's Glam test on Sepolia. On Aptos, however, use remains optional and requires a compatible wallet or application.

Aptos Joins Existing MEV Defenses

mev bots are getting blinded. @Aptos just flipped the script on sandwich attacks with its encrypted mempool. how it works: your transaction details (assets, amounts) are encrypted on your device. validators order the block *blindly*, then jointly decrypt it only after the…
— cryptonow (@manhhuynh2310) October 13, 2026

The launch responds to a recorded trading risk across networks. Ethereum traders experienced sandwich-attack losses of roughly $60 million during the 12 months ending October 2025. Bitquery noted nearly 6.9 million sandwich attacks on Solana over 11 months, affecting about 2.2 million wallets and producing $29.7 million for bots. Loss figures at that scale help explain why transaction-visibility defenses have moved into live protocol features across networks.

Gnosis Chain introduced an encrypted mempool with Shutter in July 2024, while Ethereum's Flashbots Protect directs transactions privately to block builders. Together, the two illustrate the broad shapes of MEV defense now in operation: hiding transaction contents until ordering is locked, or keeping orders out of the public queue altogether. Aptos claims its method differs because current validators manage both ordering and decryption, avoiding a separate committee or trusted builders.

Users can access the protection by opting in via a compatible wallet or application, and a gas-price floor applies to encrypted submissions. How much order flow ends up encrypted—given the added gas cost and the requirement for supporting software—is the practical measure of how far the protection reaches.

Source: 99Bitcoins