Pre-Registration Hash

A Pre-Registration Hash is a cryptographic commitment, typically a hash of the future transaction's details (sender, recipient, amount, nonce). This allows a user to signal intent to the network without revealing the transaction's sensitive data until it is ready for final execution, preserving privacy during the ordering phase.

By submitting only a hash, users prevent front-running and other forms of Maximal Extractable Value (MEV) exploitation. Sequencers or block builders can order these commitments without knowing which transactions will be most profitable to manipulate, leading to a more equitable ordering of transactions in the final block.

The process follows two distinct phases:

• Pre-Registration Phase: Users submit the hash of their intended transaction to a sequencer.
• Revelation Phase: After ordering is determined, users submit the full, signed transaction that corresponds to the pre-registered hash. The sequencer validates the match before inclusion.

The sequencer is responsible for collecting pre-registration hashes, determining a fair order, and publishing a commitment to that order (e.g., in a root hash). This creates soft finality for users regarding their transaction's position. The sequencer must later reveal the full, valid transactions that correspond to the ordered hashes.

The system's security relies on the cryptographic binding between the hash and the final transaction. It uses properties of cryptographic hash functions:

• Hiding: The hash reveals nothing about the input.
• Binding: It is computationally infeasible to find a different transaction that produces the same hash (collision resistance).

Pre-Registration Hashes are a core component of encrypted mempool designs, such as those proposed for Ethereum by Flashbots. They allow transactions to be submitted privately to a network of builders, who compete to create blocks without seeing the transactions' plaintext contents, thereby mitigating harmful MEV.

By committing to a transaction's intent (via a hash) before it is publicly broadcast, the mechanism eliminates the risk of Miner Extractable Value (MEV) bots and other network participants from seeing and exploiting pending transactions. This ensures fairer execution prices for users.

The hash acts as a secure, verifiable token for complex multi-party operations that must be arranged privately. This is critical for decentralized exchange (DEX) limit orders, batch auctions, and cross-chain swaps, where terms are negotiated before final settlement.

Failed transactions or rejected orders are handled off-chain, consuming no gas fees. Only the final, agreed-upon transaction is submitted to the blockchain, optimizing network resources and lowering costs for all participants.

The initial commitment reveals only a hash of the transaction details, not the actual parameters (like token amounts or addresses). This obscures user intent during the coordination phase, providing a layer of privacy against network surveillance.

The cryptographic link between the hash and the final transaction ensures that the executed on-chain action exactly matches the pre-committed terms. Any tampering or deviation will cause the transaction to fail, protecting all parties.

This mechanism is foundational for off-chain order books used by DEXs like CowSwap and UniswapX. It allows users to place intent-based orders that are matched by solvers without revealing their strategy until it is securely executed.

The hash acts as a cryptographic commitment, binding a user to a specific piece of data (e.g., a bid, a vote, a state) at a specific time. Once the hash is submitted, the user cannot later deny or alter the original data without detection. This property is foundational for fair sequencing and MEV protection mechanisms, ensuring participants cannot equivocate.

When the full data is later revealed, the system recalculates its hash and compares it to the stored Pre-Registration Hash. A mismatch immediately proves the data has been tampered with, causing the transaction to be rejected. This provides tamper-evident security, guaranteeing that the executed logic matches the user's original, committed intent.

By submitting only a hash, the actual transaction details remain hidden from the public mempool. This prevents front-running bots and sandwich attacks that rely on observing plaintext transaction data. Protocols like CowSwap and Flashbots SUAVE use this principle to protect user transactions from predatory MEV.

Security relies on the cryptographic strength of the hash function (e.g., Keccak256). Collision resistance ensures it is computationally infeasible to find two different inputs that produce the same hash. A weak hash function would allow an attacker to substitute malicious data after commitment, breaking the system's integrity.

A Pre-Registration Hash must be uniquely bound to a context to prevent replay attacks. This is typically achieved by including in the hashed data:

• A nonce (sequence number)
• A chain identifier
• A deadline or block number Without this, a valid hash from one context could be maliciously reused in another.

Common vulnerabilities include:

• Weak Randomness: Using predictable data (like blockhash) in the hash allows pre-computation.
• Gas Griefing: An attacker can force a user to reveal data at a high gas cost.
• Revelation Deadline: If the window to reveal data is too short, users may lose funds; if too long, it creates systemic uncertainty.
• Oracle Manipulation: If external data is part of the commitment, compromised oracles break integrity.

A Pre-Registration Hash is a one-way hash (e.g., keccak256) of a user's wallet address and a protocol-specific secret. This creates a commitment that proves early participation without revealing the final eligibility criteria or distribution formula until the protocol is ready to reveal and verify the data.

Protocols use this mechanism to prevent Sybil attacks and ensure a fair distribution. Users commit their address during a pre-launch phase. Later, the protocol can verify the hash against a finalized merkle tree or allowlist to determine eligibility for token claims, often rewarding early supporters.

• Phase 1: Commitment: User signs a message or interacts with a smart contract to generate their unique hash.
• Phase 2: Protocol Finalization: Protocol determines final rules and generates a merkle root from all valid commitments.
• Phase 3: Claim: User submits a merkle proof derived from their original hash to claim their allocation from the finalized contract.

Typically implemented via a commit-reveal scheme using a smart contract. The contract stores only the hash during the commit phase. The reveal phase involves submitting the original pre-image (address + secret) for on-chain verification. This pattern is common in ERC-20 airdrops and NFT allowlist mints to manage gas efficiency and prevent front-running.

• Anti-Sybil: Makes it costly for attackers to game the system after rules are set.
• Flexibility: Allows protocol teams to finalize distribution parameters after gauging community interest.
• Gas Efficiency: Final claim transactions can be optimized using merkle proofs, reducing overall network congestion at launch.

A prominent Layer 2 scaling solution used a Pre-Registration Hash system for its governance token airdrop. Users who bridged assets or conducted transactions before a snapshot date could generate a hash. Months later, they submitted merkle proofs to claim tokens, with the hash ensuring their early activity was immutably recorded and verifiable.

A cryptographic protocol where one party commits to a chosen value, keeping it hidden, and later reveals it. The pre-registration hash is the commitment. Key properties:

• Binding: The committer cannot change the value after committing.
• Hiding: The commitment reveals nothing about the value. This is foundational for zero-knowledge proofs and blockchain data availability.

A hash-based data structure that efficiently verifies large datasets. A Merkle root is a single hash representing all underlying data. In pre-registration, a user might commit to a Merkle root of their data. Verifiers can later prove specific data was included using a Merkle proof, without needing the entire dataset.

A method where a prover convinces a verifier a statement is true without revealing the underlying information. Pre-registration hashes are often used within ZKPs:

• The prover commits to private inputs with a hash.
• The ZK circuit uses this commitment to generate a proof of correct computation.
• The original data remains private.

The guarantee that data necessary to validate a blockchain's state is published and accessible. Data availability sampling and data availability committees rely on commitments (like hashes of data blobs) to ensure data can be retrieved. A pre-registration hash can act as a compact promise that specific data will be made available.

A function that requires a sequential number of steps to compute, but whose output can be verified quickly. VDFs are used to create unpredictable randomness (e.g., for leader election). A pre-registration hash can commit to an input before the VDF computation begins, preventing manipulation of the result.

A Layer 2 scaling solution that batches transactions off-chain and submits a validity proof (ZK-SNARK/STARK) to the main chain. The rollup operator publishes a state root (a commitment hash) and a proof. Users' pre-registered transactions are included in the batch, with the hash ensuring their data is part of the proven state transition.