Blinded Block

The core mechanism of a blinded block is a two-phase commit-reveal scheme. First, a builder commits to a block header (a cryptographic commitment) without seeing the transactions. After this commitment is accepted by the proposer, the builder reveals the full block contents. This prevents the proposer from stealing the profitable transaction order.

Blinded blocks enforce a clear separation between block builders and block proposers (validators).

• Builders: Compete to create the most valuable block from the mempool.
• Proposers: Simply select the block with the highest bid from a list of blinded commitments. This separation removes the proposer's ability to censor or reorder transactions for profit.

By blinding the transaction data from the proposer, this design directly combats harmful MEV strategies that rely on information asymmetry, such as:

• Frontrunning: A validator cannot see and insert their own transaction ahead of a user's lucrative trade.
• Sandwich Attacks: The proposer cannot position transactions around a known victim trade. This leads to fairer execution for end users.

Blinded blocks create a competitive builder market. Builders receive transaction flow, construct optimized blocks, and submit bids (the fee they will pay to the proposer) alongside their blinded block commitment. The proposer's economic incentive is simplified: they always choose the highest bid, which typically corresponds to the most economically efficient block.

Proposer-Builder Separation (PBS) is the primary framework for implementing blinded blocks, notably in Ethereum's roadmap. It can be enacted in two ways:

• Enshrined PBS: A permanent protocol feature.
• Out-of-protocol PBS: Implemented via a trusted relay, which acts as an intermediary to receive blinded blocks and forward the highest bid to the proposer.

In current out-of-protocol implementations, a relay is a critical component that facilitates the blinded block market. The relay:

• Receives block commitments and bids from builders.
• Validates block correctness (e.g., proof of execution).
• Presents the highest valid bid to the proposer. This introduces a trust assumption, as the relay must be honest and not censor builders. Enshrined PBS aims to eliminate this trusted role.

The core goal is to decouple the role of block builder from block proposer. The builder assembles the block with transactions and a fee, creating a blinded block header. The proposer (e.g., a validator) simply signs this header without seeing the contents, preventing them from censoring or front-running transactions.

By blinding the proposer to the transaction order and contents, the system reduces the incentive for validators to run sophisticated MEV extraction strategies themselves. This helps prevent the centralization of block production power into a few entities that can capture the most value, promoting a more decentralized and fair network.

A proposer who cannot see the specific transactions in the block they are signing cannot easily exclude certain transactions (e.g., from sanctioned addresses). The censorship decision is pushed to the competitive builder market, where many builders may include the transaction if it is profitable, making network-level censorship more difficult.

Blinded blocks create a marketplace where specialized block builders compete to create the most valuable block (highest fees + MEV) for the proposer. Proposers select the block with the highest bid attached to the blinded header, ensuring they capture value without needing complex infrastructure.

Blinded blocks are the technical mechanism that enables Proposer-Builder Separation (PBS), a key architectural upgrade for Ethereum. PBS formalizes the roles, with builders submitting execution payloads to a relay, which then presents the blinded header and bid to the proposer.

Blinding simplifies the validator's operational requirements. They no longer need to run a full mempool or complex MEV-boost software. They simply evaluate signed headers from relays, reducing resource needs, latency sensitivity, and the risk of being slashed for including invalid transactions they didn't see.

A blockchain design pattern that decouples the role of block proposer (who chooses the next block) from the block builder (who constructs it). This separation is enforced by the blinded block mechanism, where the proposer commits to a block header without seeing its full contents, mitigating centralization risks from MEV extraction.

The compact, 80-byte summary of a block containing critical metadata like the previous block hash, Merkle root, timestamp, and nonce. In PBS, the builder provides a blinded block consisting of just this header to the proposer for signing, hiding the full transaction list and execution payload.

The main body of a block containing the actual list of transactions and their results (state changes). This is the component kept hidden from the proposer in a blinded block scheme. The builder reveals it only after the proposer has cryptographically committed to the block header.

The profit a block producer can extract by including, excluding, or reordering transactions. Blinded blocks are a primary defense against MEV-driven centralization, as they prevent the proposer from seeing the transaction mempool and manipulating it for personal gain before the block is finalized.

A trusted or trust-minimized intermediary in PBS networks. Builders submit their complete blocks (header + payload) to relays. Relays then forward only the blinded block (header) to proposers. This prevents proposers from stealing block content and ensures fair builder competition.

A two-phase cryptographic protocol where a party first commits to a value (e.g., a block header hash) and later reveals the original data. Blinded block propagation uses this pattern: the proposer commits to a header, then the builder reveals the full block, enabling verification that they match.