Background and motivation of EIP-7732
Since the MEV problem is difficult to solve from the root, taking fair competition measures is the only way to avoid security risks. After the Ethereum merger, in order to maintain fairness and reduce the scale effect of large staking pools on MEV extraction, Flashbots launched MEV-Boost, which adopts the PBS (Proposer-Builder Separation) mechanism to reduce the chances of validators directly participating in MEV activities and diversify MEV stakeholders. Currently, the MEV-Boost block accounts for more than 90%.
With the widespread adoption of MEV-Boost, the Ethereum community began to worry about the security risks that may arise from relying on this third-party service. Therefore, the idea of implementing PBS within the Ethereum protocol was born, called ePBS (Enshrined Proposer-Builder Separation). Recently, ePBS was given an official EIP number: EIP-7732. EIP-7732 is a change to the consensus layer without changing the execution layer. The core is to logically and temporally separate execution verification from consensus verification, and postpone execution verification until after consensus verification is completed.
In addition to solving the problem of validators relying on third parties (such as MEV-Boost) to build execution payloads, the proposal of EIP-7732 also aims to optimize efficiency in the verification process. Currently, validators must complete all consensus and execution state transition functions in a very short time (within 4 seconds), which places extremely high demands on computing resources and network bandwidth. During this window period, validators need to verify and confirm a large amount of transaction information and update the status of the blockchain, which not only increases the computational burden of a single node, but also increases the possibility of errors. By separating execution verification and consensus verification, it is ensured that within the critical 4-second window, nodes only need to complete relatively few tasks, thereby reducing the computational burden and speeding up network propagation.
The core content of EIP-7732
EIP-7732 creates a new role "Builder", which is a new optional responsibility for validators. Any validator with sufficient funds to stake on the beacon chain and the ability to perform block construction tasks can become a builder. Builders are responsible for building and submitting commitments to execute payloads. Validators can now outsource the construction of payload execution to builders, and focus more on consensus-level tasks.
The execution payload is the core part of the block, which contains all the transaction and state change information. The process of building the execution payload includes selecting transactions from the memory pool, sorting transactions, executing transactions in sequence, and packaging all the information to form the execution payload.
To achieve this separation, EIP-7732 removes the ExecutionPayload field, which contains all data related to the transaction execution, such as the transaction list and state transition results. By removing this field, the creation and verification of the execution content is separated from the creation and verification of the beacon block. Instead, EIP-7732 introduces a new data structure SignedExecutionPayloadHeader, which includes the builder's commitment to the execution payload to be revealed in the future.
Overall process
Builder's Tasks: The builder is responsible for creating the execution payload and generating a commitment to publicly disclose the execution payload. The commitment is encapsulated in the SignedExecutionPayloadHeader data structure, which includes the hash of the execution payload and the digital signature of this hash to ensure the immutability of the data and the verification of the source. This commitment indicates that the builder will disclose the complete execution payload at a certain time in the future, and stipulates the amount to be paid to the beacon block proposer to incentivize the beacon block proposer to include this commitment.
Beacon block proposer's tasks: Beacon block proposers (validators) work with builders to create new beacon blocks without directly processing the execution details of transactions, but include commitments provided by builders, and then broadcast the entire beacon block to the Ethereum network to reach consensus. Including only commitments can reduce the burden on the network and speed up the propagation and consensus verification process of beacon blocks. After processing the builder's commitment, the tip in the commitment will be deducted from the builder's beacon chain balance and credited to the beacon block proposer. After the beacon block proposer successfully broadcasts the beacon block containing the commitment, the builder needs to disclose the complete execution payload within the specified time window.
PTC Verification: In order to monitor whether the builder publicly executes the payload in a timely manner, a group of validators randomly selected by the beacon chain network form the Payload Timeliness Committee (PTC). PTC is responsible for checking whether the builder has publicly executed the payload that matches the commitment within the specified time window. If the builder fails to disclose it in a timely and correct manner, PTC will broadcast a negative result and the builder will face a penalty of slashing the stake. If the PTC verification passes, the full verification of the execution payload is postponed to the next beacon block for separate processing, which is delayed verification.
In addition, the proposal also introduces regulatory rules and a new penalty mechanism for PTC to ensure the rigor and fairness of the entire verification process. At the same time, due to the separation of execution payloads and beacon blocks, the fork selection logic has also been adjusted to adapt to the new verification process. These changes are expected to significantly improve the security and efficiency of the network. Through a series of designs, EIP-7732 improves Ethereum's processing efficiency and reduces network latency.