Delayed Proof of Work (dPoW)


Delayed Proof of Work (dPoW) is a second-layer consensus security mechanism, designed to protect blockchains from 51% attacks threatening the integrity of the network.

What Is Delayed Proof of Work (dPoW)?

Delayed Proof of Work (dPoW) is a second-layer consensus security mechanism, designed to protect blockchains from 51% attacks threatening the integrity of the network. It does this by leveraging the hash rate of an external Proof of Work (PoW) network and applying it on top of a network’s existing consensus mechanism. 

Proof of Work and Proof of Stake

PoW can be defined as the process of adding new blocks of transactions in a blockchain through a consensus algorithm where miners solve complex problems. 
PoW blockchains require a high amount of computational power (hash rate) in their mining process, which can be very costly, with a strong dependency on network consensus. The high computing power requirements usually form a high barrier to entry. Hence, it leaves PoW networks more susceptible to a 51% attack where a single or group of malicious actors gain majority control of the mining power and ultimately compromise the network. 
Proof of Stake (PoS) is another type of consensus mechanism where validators stake capital as a form of economic incentive to act in the network’s best interest. Ethereum, one of the largest blockchain networks, was originally launched with a PoW consensus mechanism before implementing a huge protocol change to PoS in September 2022, known as ‘The Merge’. 

If validators act in a malicious or inefficient manner in PoS networks, the validator’s staked capital will be lost and redelegated. Thus, PoS networks do not require extra energy to prove trustworthiness, making them more eco-friendly and secure than PoW. 

The Importance of Hashpower

While larger blockchains are able to achieve a high hash rate, it is difficult for smaller blockchain networks to reach the same level of security when their hash power is much lower. dPoW provides access to a higher hash rate to create an impenetrable security layer to mitigate 51% attacks.

dPoW uses an external blockchain’s hash power (i.e. Litecoin) to enhance its own network security. A group of notary nodes adds data from the first blockchain onto the second to take advantage of the security of the secondary blockchain. Both blockchains would have to be compromised to undermine the security of the first. 

The notary nodes write a block hash from every dPoW-protected blockchain onto the Komodo blockchain and on Litecoin —the leveraged blockchain. These blocks are backed up on multiple blockchain networks, known as notarized blocks, where the history of every chain using dPoW becomes immutable.

Every 10 minutes, the decentralized network’s system takes a snapshot of its own blockchain. These snapshots are hashes of files that are now backed up on the chosen PoW blockchain and act as a guarantee to all parties that the authenticity and integrity of data have not been compromised. 

Additionally, the notary nodes in a dPoW network have the freedom and flexibility to switch notarization to another PoW network if the hashing power of miners worldwide changes to another PoW network, or the cost of notarization on the current PoW network becomes too costly, among other reasons. Having such flexibility allows a dPoW network and its ecosystem to maintain a superior level of security and adaptivity compared to other networks like Bitcoin. 

The Difference Between dPoW and Other Mechanisms

A security mechanism like dPoW does not use a consensus algorithm like PoW or PoS. Instead, it makes it impossible for blocks that have been notarized to be reorganized, not abiding by the “longest chain rule” used by PoW chains. 

The longest chain rule represents the chain of blocks that took the most energy to build, which for the most part would be the chain with the most blocks added to it, hence giving the rule its name. However, there are instances where the chain that requires more energy to build is not the one with the most blocks on it. 

This is due to the changes in difficulty where new blocks may encounter different levels of difficulty and require additional work to solve. The difficulty period resets every two weeks to regulate the 10-minute intervals where blocks of transactions are added to the blockchain. 

If blocks are being added too quickly, the difficulty and mining power to solve them will increase. A shorter chain with a greater amount of chainwork would be adopted by the nodes in accordance with the “longest chain rule”. By abiding by this rule, it ensures that every node on the network agrees on what the blockchain looks like, and thus agrees on the same transaction history.

dPoW does not recognize the longest chain rule for any transactions that are older than the most recent backup on the network. For instance, when a PoW network receives a notarized block that begins at XXX1, it will apply the longest chain rule at XXX2. In contrast, when a dPoW network receives a notarized block, it will not accept a chain that begins at XXX0 even if it is the longest chain. Instead, it refers to the latest backups that were placed into its chosen PoW blockchain.

Advantages to dPoW

The dPoW security mechanism enables the network to conduct frequent backups on the leveraged PoW network, which the consensus mechanism will look to find the most accurate record when a transaction is older than the most recent backup. In the event of a system failure or hack, data can be easily recovered and the extent of such damage would require the hacker to have successfully infiltrated the leveraged blockchain and destroyed all backups within the blockchain. 

If a third-party smart chain employing dPoW security is compromised, it would require all copies of the smart chain, main dPoW network and the chosen PoW network in which the dPoW backups are, to be destroyed. This enables the dPoW network ecosystem to benefit greatly from the added level of security while enjoying a lower cost financially and environmentally.

The key difference between a main chain and a smart chain is that the smart chain is notarized to the main chain’s security, which is notarized to an external PoW network. As each notarization is built upon all the notarizations that came before, the dPoW security mechanism only requires the most recent iteration. In the event that the chosen PoW network fails, the notary node is able to conduct its next notarization process on a competing PoW network to secure the network’s ecosystem based on the most recent notarization. 

The dPoW security mechanism enables blockchains to utilize the security of a secondary blockchain, which is especially useful for newly formed blockchains that are often vulnerable due to their low hash rate.

Author: Kadan Stadelmann, CTO of Komodo, a leader in blockchain interoperability and atomic swap technology. 

Kadan Stadelmann is a blockchain developer, operations security expert, and Chief Technology Officer of Komodo, an open-source technology provider that offers all-in-one blockchain solutions for developers and businesses. Komodo works closely with organizations that want to launch their own custom decentralized exchanges, DeFi platforms, and independent blockchains. Its flagship technology and end-user application is AtomicDEX - a mobile and web-compatible non-custodial multi-coin wallet and atomic swap-powered DEX rolled into one dApp. Kadan strongly identifies with Komodo’s open-source vision and ideology. His dedication to the Komodo project is founded on an unwavering desire to make the world a better place. In addition to cryptography, blockchain technology, and development, Kadan is interested in literature, mathematics, astrophysics, and traveling.