Delayed Proof-of-Work

3 min read

Pronunciation

[di-leyd proof-uhv-wurk]

Analogy

Think of Delayed Proof-of-Work as a small town hiring the security services of a much larger city. The town maintains its own local police force (native ) for day-to-day operations and first response, but periodically sends snapshots of important records to be stored in the larger city's heavily fortified vault (Bitcoin ). If criminals ever overpower the local police and try to rewrite the town's records (51% attack), the tamper-proof copies in the distant vault can prove what the original records contained. This arrangement gives the small town security that approaches the level of the big city, without having to maintain an equally expensive security force or surrender its self-governance.

Definition

A security mechanism that enhances the protection of smaller blockchains by periodically recording their data onto a more secure, higher -rate like . Delayed Proof-of-Work (dPoW) allows chains to maintain their own rules while leveraging the security of a more established network to prevent 51% attacks, creating a layered security approach without sacrificing independence.

Key Points Intro

Delayed Proof-of-Work implements four key innovations that create its layered security approach.

Key Points

Notary Nodes: Specialized validators elected by stakeholders that periodically create checkpoints of the blockchain's state.

Cross-Chain Notarization: Process of recording cryptographic fingerprints of the smaller chain onto the security chain through specialized transactions.

Independent Consensus: Allows the protected blockchain to maintain its own consensus rules and block validation process for normal operations.

Security Inheritance: Leverages the accumulated proof-of-work of the security chain to protect against deep reorganization attacks.

Example

A privacy-focused with moderate power implements Delayed Proof-of-Work to protect against potential 51% attacks. The operates normally using its own mechanism for validation and creation. Every 10 minutes, special elected notary nodes create a checkpoint by taking a cryptographic of the current and recording it in a . If an attacker later acquires a majority of the network's power and attempts to rewrite history, they would need to not only overpower the original network but also create an alternative version of the from the point where the checkpoint was recorded—a computationally and economically infeasible task given 's massive power. This allows the smaller to achieve security approaching that of without adopting 's rules or limitations.

Technical Deep Dive

Delayed Proof-of-Work implements a multi-layered security architecture through a notarization process involving specially elected nodes. Notary nodes are selected through a -weighted voting mechanism where network participants elect approximately 64 nodes per season (typically lasting one month). These notary nodes participate in a modified Tendermint-based to agree on checkpoints of the protected chain, requiring 13 notaries to form a notarization . The notarization process involves creating a special containing the of the protected chain, which is then submitted to the security chain (typically ) through a pay-to-script-hash output with multiple notary signatures. The system employs a backup notarization mechanism to an alternative security chain (typically Litecoin) as a redundancy measure. For validation, nodes on the protected chain can verify the existence of notarization transactions on the security chain through simplified payment verification (SPV) proofs. The protected chain implements rules that prevent reorganizations beyond the most recent notarized , effectively limiting the depth of possible chain rewrites to the notarization interval (typically 10-30 minutes), regardless of power. This creates a security model where attacking the protected chain becomes as difficult as attacking the security chain after the notarization confirms, while maintaining the protected chain's independence for rules, features, and governance.

Security Warning

While Delayed Proof-of-Work provides strong protection against deep reorganizations, the security guarantees only apply after notarization is confirmed on the security chain. For high-value transactions, wait until at least one notarization has been confirmed before considering the finalized.

Caveat

Despite its security benefits, Delayed Proof-of-Work introduces additional complexity and potential points of failure. The system depends on the reliable operation of notary nodes, creating a semi-centralized security layer that could become a target for attacks or collusion. The notarization process also adds to achieving final security guarantees, creating a trade-off between immediate and ultimate security. Additionally, the mechanism depends on the continued operation and accessibility of the security chain, potentially exposing the protected chain to risks if the security chain undergoes significant changes to its or fee structure that might affect the viability of the notarization process.

Related Terms

dPoW

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