What is Proof of History (PoH)?

Imagine a world where every digital event carries with it an irrefutable time stamp, a mark that certifies its existence at a precise moment. This is the dream that Proof of History (PoH) makes possible. And in the universe of blockchains, where trust and security are fundamental pillars, PoH emerges as an innovative solution to one of the greatest challenges: scalability.

Traditionally, blockchains have struggled with slow transaction processing, a bottleneck that limits their mass adoption. Proof of History, developed by Solana Labs, introduces a revolutionary way of recording time directly on the blockchain, eliminating the need for a centralized time source. This advancement not only speeds up the transaction validation process, but also lays the foundation for high-performance blockchains capable of handling thousands of transactions per second.

In this article, we will explore in depth what Proof of History is, how its intricate mechanism works, and what are its advantages and disadvantages compared to other consensus protocols such as Proof of Work (PoW) and Proof of Stake (PoS)Join us on this journey to discover how PoH is transforming the blockchain landscape and paving the way to a faster, more efficient decentralized future.

What is Proof of History (PoH)?

Proof of History (PoH) is an innovative consensus protocol that introduces a new way of timestamping blockchains. At its core, PoH uses a cryptographic function called Verifiable Delay Function (VDF) to create a sequence of hashes that are not only unique, but also verifiable and resistant to tampering. In this way, each hash in this sequence contains information about the previous hash, creating a continuous chain of historical evidence. This is what allows for the creation of such a «chain of historical events», which allows you to trust the data processed and protected by Proof of History.

Now, the beauty of PoH lies in its ability to allow every node on the network to independently verify the order and validity of transactions without needing to communicate with other nodes. This ability eliminates the latency associated with traditional consensus protocols, where nodes must agree on the order of transactions before they can be validated.

To better understand its function, let’s think about an athletics competition during the Olympics. If we take a photograph of the competition, it becomes proof that the event occurred at a specific time. Similarly, PoH creates a historical record that proves that an event occurred at a precise time.

How does Proof of History (PoH) work?

Of course, there is a lot of engineering behind Proof of History (PoH), but certainly the heart of it all is the Verifiable Delay Function (VDF). A VDF is a cryptographic function that requires a specific amount of time to evaluate, but can be verified very quickly. In the context of PoH, the VDF is used to generate a sequence of hashes that serve as cryptographic timestamps.

The process works as follows:

1. initial entry: Represents the starting point of the process, which is a hash of the previous block or any other relevant data.
2. Execution of the VDF: Indicates that the Verifiable Delay Function (VDF) takes the initial input and performs a series of sequential calculations to produce a single output.
3. Hash creation: Shows that the output of the VDF is used to create a new hash, which becomes the timestamp for the current block.
4. Hash included in the block: Represents the hash that is included in the new block and propagated through the network
5. Independent verification: Indicates that every node in the network can verify the validity of the timestamp by running the VDF with the initial input and comparing the result to the hash included in the block.
6. Valid timestamp: The timestamp is considered valid if the two match.
7. Invalid timestamp: The timestamp is considered invalid if the two do not match.

A concrete example of how this is implemented is on the Solana blockchain. Solana uses the SHA256 hash function to record all events and transactions on the blockchain. Each output of a transaction becomes the input for the next hash, creating a continuous sequence of historical proofs.

Pros and Cons of Proof of History (PoH)

Of course, this allows Proof of History (PoH) to offer a number of significant advantages over traditional consensus protocols:

1. Offers greater scalability: By removing the need for constant communication between nodes to validate transactions, PoH allows for greater scalability and significantly higher throughput.
2. Lower latency compared to other consensus protocols: The ability to independently verify transactions reduces latency and allows for faster block confirmation. Once a block is added to the blockchain, it is immediately finalized.
3. Superior energy efficiency: Unlike Proof of Work, which requires a large amount of computational power, PoH uses the VDF to generate timestamps, resulting in lower power consumption.
4. A good level of security in relation to scalability:The cryptographic timestamps created by the VDF are tamper-resistant, ensuring the integrity and security of the blockchain.

But like everything, despite its many advantages, Proof of History also has some disadvantages that should be taken into account:

1. Potential centralization: PoH requires a large amount of computational power on each node, which could limit the number of nodes that can participate in the network. This could lead to further centralization, especially if only a few nodes have the resources to run the VDF efficiently.
2. Reliance on a reliable time source: Although PoH eliminates the need for a centralized time source for transaction validation, it still relies on a trusted time source to generate the initial sequence of hashes. If this time source were to be compromised, it could affect the integrity of the blockchain.
3. Relative novelty: Compared to PoW and PoS, PoH is a relatively new protocol and has not been as widely tested in the real world. This means that there may still be unforeseen vulnerabilities or issues that need to be addressed.

To get a clearer view of how Proof of History compares to other consensus protocols, here is a comparison table highlighting key differences across five important factors:

Examples of using Proof of History

While Solana is the most prominent example of a blockchain using Proof of History, there are other projects that are also exploring or using this consensus protocol:

• Filecoin: Filecoin is a decentralized storage network that uses a variant of Proof of History to verify that data is being stored correctly over time
• Hashgraph: Hashgraph is an alternative consensus protocol that also uses a form of temporal sequencing to achieve high throughput and low latency.

These examples demonstrate the versatility of Proof of History and its potential to improve the efficiency and scalability of a wide range of blockchain applications.

The future of Proof of History

All in all, Poof of History represents a significant advancement in the quest for faster, more efficient, and more scalable blockchains. While it still has some challenges to overcome, its ability to eliminate the need for constant communication between nodes and to create tamper-resistant cryptographic timestamps makes it a promising technology for the future of blockchains.

But, as blockchain technology continues to evolve, we are likely to see more projects exploring and adopting Proof of History as a way to improve their performance and scalability. Over time, PoH could become a standard consensus protocol for applications that require high throughput and low latency.