mev-commit is a novel protocol designed to enable preconfirmations in blockchain environments. Specifically, it facilitates the secure and private exchange of:

1. Execution bids - Requests from bidders (like mev searchers or L2 sequencers) to have their transactions executed in a specific way.
2. Cryptographic commitments - Promises from providers (like block builders or proposers) to execute those bids as specified.

Privacy is crucial for preconfirmations because commitments could leak information about block contents and value. When bids are visible, competitors could adjust their strategies or front-run transactions, and some parties could gain an unfair advantage and manipulate the market. If, for example, the total value of a block under construction is leaked, this would be analogous to seeing the aggregate value of all pending orders in an orderbook, which would affect bidding strategies and lead to underbidding by competing block builders. This kind of information asymmetry, where some participants have more or earlier access to bid data, leads to significant competitive imbalances in the mev ecosystem, much like how high-frequency traders with faster data feeds gain an edge in traditional markets.

mev-commit employs two key components to ensure privacy, both of which have applications beyond mev and blockchain environments:

• Anonymous Receiver-Updatable Broadcast Encryption (ARUBE): ARUBE allows bidders to securely send bids to a chosen subset of providers without revealing what other providers they're working with. This cryptographic primitive allows for the granular selection of transaction details to be encrypted, or otherwise left public.
• Dual-Phase Commitment Scheme (DPCOM): DPCOM enables secure commitment to bids in two phases, allowing both bidders and providers to open commitments while maintaining privacy as long as necessary.

These cryptographic innovations represent advancements in privacy-preserving technologies with potential impact across other fields that require secure, selective, and verifiable information exchange. In mev-commit they enable the following:

• By keeping bids private, mev-commit prevents unauthorized parties from gaining insight into trading strategies or order flow. This protects against front-running and other exploitative behaviors that can occur when MEV opportunities are prematurely revealed.
• The commitments made by providers (e.g. block builders) are kept confidential until settlement. This is crucial for maintaining the integrity of processes like the mev-boost auction, as it prevents competing providers from deducing the value or content of committed bids. Without this privacy, block builders could gain unfair advantages by inferring the total value of blocks under construction by their competitors.
• The mev-commit chain enables decentralized recording and settlement of agreements between bidders and providers. These agreements remain private until the relevant block is confirmed. This allows for real-time commitments while still maintaining confidentiality of block contents until execution.

The ability to enter into private, binding agreements that are settled in a decentralized manner opens up new possibilities for complex mev strategies and fair competition among market participants.

ARUBE: Protecting Bid Privacy

ARUBE provides anonymity by ensuring only the intended provider knows if they are in the recipient set, and confidentiality by preventing eavesdroppers from learning bid contents. This prevents competitors from seeing bids and allows bidders to selectively disclose information to trusted providers.

In our introduction to mev-commit, we likened preconfirmations to the user experience of ordering a package from Amazon. Along those lines, ARUBE can be thought of as a sort of postal system for classified documents. Here, a sender (the bidder) wants to send secret messages to specific recipients (providers) without revealing who those recipients are.

In this system, each potential recipient can be thought of as having a mailbox with a unique lock. The sender creates a master key that can open the envelopes in which the messages will put. Copies of this master key are then put into the boxes of the chosen recipients. Afterwards, the envelopes with the messages can be broadcast freely and only the chosen recipients can open them with the master key.

How this works in mev-commit is as follows: in the setup process, providers generate and share public keys while keeping their secret keys private. Bidders can define and update their set of preferred providers, encrypting a secret key for each chosen provider. Bids are encrypted using a symmetric key and sent to all providers, but only those in the chosen set can decrypt them.

In terms of preconfirmations, this means that when a bidder seeks a preconfirmation for their transaction, they can selectively disclose their bid to a subset of trusted providers. For example, a bidder might send their encrypted bid to their choice of providers through a direct connection, after which point the provider must send the commitment to the chain to record it, and if the process of recording it to the chain were not private, valuable information could be leaked.

Instead, only those builders previously selected will be able to decrypt and potentially commit to including the transaction. This selective disclosure allows bidders to manage their risk and maintain privacy while still reaching a sufficiently wide pool of providers to ensure their transaction gets included. Other providers would not receive the encrypted bid, and would gain no information about its contents or even which providers can decrypt it, aside from the fact that everyone can see that a commitment was made, thus maintaining the bidder's privacy and strategic advantage.

DPCOM: Securing Commitments