Proof of History

• Michael Willson
• April 05, 2025

Blockchain technology has revolutionized how we think about trust and security in the digital age, enabling decentralized networks to operate without intermediaries. However, one of the key challenges of Blockchain networks is scalability, particularly when processing numerous transactions quickly and securely. This is where Proof of History (PoH) comes in. PoH is a novel consensus mechanism developed by Solana Labs that uses a cryptographic function called Verifiable Delay Function (VDF) to generate timestamps for each block in the Blockchain. By ensuring the immutability and authenticity of these timestamps, PoH can significantly improve the efficiency and security of Blockchain networks, particularly those that require high transaction throughput and fast finality. 

Considering its operating efficiency, Proof of History can soon be seen as the primary consensus mechanism used in developing decentralized financial systems. This enhances the importance of Proof of History for Blockchain engineers and architects working with Web3-based DApp ecosystems. This article will explain the concept of Proof of History, how it works, its benefits, and its potential to transform the Blockchain industry.

Let’s get started!

What is Proof of History?

Proof of History (PoH) is a novel consensus mechanism developed by Anatoly Yakovenko, the founder of Solana Labs. The concept behind PoH is that the order of events is just as important as the events themselves in a Blockchain network, and the ability to prove the order of events is essential for maintaining the integrity of the network. To achieve this, PoH uses a cryptographic Verifiable Delay Function (VDF) to generate a timestamp for each block in the Blockchain.

The VDF is designed to be delay-hard and memory-hard, making it difficult for attackers to manipulate the timestamps. The timestamp generated by the VDF is then incorporated into each block in the Blockchain, providing a verifiable and immutable record of the order in which transactions occurred. PoH allows for fast finality, meaning that once a block is added to the Blockchain, it is considered finalized and cannot be undone.

The PoH mechanism is used primarily in the Solana Blockchain network, designed to be highly scalable and capable of processing thousands of transactions per second. By reducing the amount of storage and bandwidth required to maintain the Blockchain, PoH can improve the efficiency and speed of the Solana network while also providing a secure and verifiable record of transactions.

How Does Proof of History Work?

Proof of History (PoH) is a unique consensus mechanism. Here’s a simplified step-by-step explanation of how it works:

• Cryptographic Timestamping: At the heart of PoH is cryptographic timestamping, which uses a sequential, pre-image-resistant hash function. This function takes an input (the current state of the Blockchain and a random seed) and produces a unique, irreversible output, known as a hash. This hash serves as a verifiable timestamp​.
• Generating a Hash Chain: Solana creates a hash chain by applying the hash function iteratively to the output of the previous hash. Each step represents a tick, with the number of hash operations indicating the time elapsed. This results in a continuous, verifiable record of time used to sequence transactions​.
• Recording Transactions: When a transaction is made, it’s sent with the most recent hash observed. Validators confirm its validity and timing by ensuring it references a hash within the current PoH sequence. This proves the transaction happened at a specific moment​.
• Consensus: Transactions timestamped with PoH are then processed using a Proof of Stake (PoS)-based consensus algorithm, Tower BFT, in Solana’s case. Validators stake SOL (Solana’s token) to participate, earning rewards for securing the network and validating transactions. Tower BFT, with the help of PoH’s timekeeping, quickly achieves consensus, allowing Solana to handle thousands of transactions per second​.
• Benefits: PoH offers several advantages, including scalability (thousands of transactions per second), low latency, high security, and energy efficiency, as it doesn’t require intensive computational resources like Proof of Work (PoW) systems​.
• Verifiable Delay Function (VDF): A core component of PoH is the VDF, which ensures block producers pass through it to access their block production slot. Solana appends the hash of data related to previously generated states in the transaction sequence, creating verifiable timestamps without the possibility of data recreation or alternative versions​​.

This revolutionary mechanism introduces a way to incorporate time directly into the Blockchain, eliminating the need for a centralized clock. This is crucial for decentralized systems,where timing transactions accurately is essential for security and efficiency​.

Proof of Work vs Proof of Stake?

Here is a breakdown of the key differences between Proof of History (PoH) and traditional consensus mechanisms like Proof of Work (PoW) and Proof of Stake (PoS):

Computational Power/Stake

PoW and PoS require participants to have significant computational power or stake in the network to participate in the consensus process. This is not the case with PoH, which relies solely on the VDF to generate timestamps.

Finality

PoH offers fast finality, which means that once a block is added to the Blockchain, it is finalized at that moment, and there is no way to revert this finalization. PoW and PoS rely on probabilistic finality, which means there is always a small chance that a block may be reversed or invalidated.

Storage and Bandwidth Requirements

PoH significantly reduces the storage and bandwidth requirements for maintaining a Blockchain network. This is because each block only needs to store a small amount of data, including the previous block’s hash and the timestamp generated by the VDF.

The Role of the Verifiable Delay Function in PoH

The Verifiable Delay Function (VDF) plays a crucial role in Proof of History (PoH), especially in the context of Blockchain technology as utilized by Solana. The essence of VDF within PoH is to ensure the creation of a historical record that demonstrates the occurrence of an event at a specific time, fundamentally acting as a decentralized clock for the Blockchain network.

In Solana’s implementation of PoH, the VDF requires a set number of sequential steps to evaluate but allows the result to be quickly and publicly verified. This process involves a sequential hash function that continuously runs over itself, using the output of the previous run as the next input. Periodically, the count and the current output are recorded, establishing a tamper-proof sequence of events. This method guarantees that time has passed between each recorded event, thus providing a secure and immutable record of transactions and events on the Blockchain​.

The VDF’s role in PoH addresses several critical aspects of Blockchain technology:

• Verifiability: It ensures the Blockchain’s historical record is transparent, immutable, and accessible for public verification. This builds trust and reduces reliance on computationally intensive processes​.
• Decentralization: Multiple nodes can generate and validate timestamps concurrently, preventing any single entity from controlling the timestamp generation. This enhances the network’s security and reliability​.
• Efficiency: By providing a reliable temporal order of events without the need for energy-intensive consensus algorithms like Proof of Work (PoW), PoH with VDF improves transaction processing efficiency, speeds up consensus, and reduces transaction fees​.

Moreover, the VDF in PoH significantly lowers the demands on data storage and bandwidth necessary for maintaining the Blockchain, as each block only needs to store minimal information, such as the hash of the previous block and the timestamp generated by the VDF​.

Applications of Proof of History

Proof of History (PoH) is a relatively new consensus mechanism that is still gaining traction in the Blockchain industry. While there are only a few examples of companies and networks currently using PoH, the potential use cases for this mechanism are significant. We have curated a detailed overview of the use cases we have developed and other potential use cases of PoH. 

Present Use-Cases of Proof of History

Proof of History (PoH) is a relatively new consensus mechanism that various companies and networks are exploring for its potential applications. One of the primary examples of a company using PoH is Solana, a high-performance Blockchain network. Solana uses PoH as its primary consensus mechanism to achieve high transaction speeds while maintaining security and decentralization.

Arweave is a decentralized storage network company that uses PoH. Arweave has announced plans to integrate PoH to improve its storage and retrieval processes while maintaining security and data integrity. Apart from these companies, PoH has also been used in developing other Blockchain projects. One is Chainlink, a decentralized oracle network that provides secure and reliable data feeds to smart contracts.

Future Use-Cases of Proof of History

While the current examples of companies using PoH are limited, numerous potential use cases exist for this consensus mechanism in the future. One potential use case is in digital identity. Using PoH to generate immutable and verifiable timestamps may create a secure and decentralized digital identity system that is resistant to tampering and fraud. This could have far-reaching implications for finance, healthcare, and e-commerce industries.

Another potential use case for PoH is in supply chain management. Creating a more transparent and secure supply chain network may be possible by using PoH to track and verify the authenticity of goods and products. This could have significant implications for industries such as food safety and pharmaceuticals, where the ability to track and verify the origin and authenticity of products is crucial. PoH could also be used in decentralized finance (DeFi). Using PoH, it may be possible to create more efficient and secure DeFi applications that can provide better financial services to users.

The potential use cases for PoH are numerous and varied. As Blockchain technology evolves, more companies and networks will likely explore its possibilities. From improved storage and retrieval processes to secure and decentralized digital identity systems, PoH has the potential to revolutionize numerous industries and bring greater efficiency, security, and transparency to the Blockchain ecosystem.

Conclusion

For readers who aspire to build a successful career in Blockchain and other Web3 technologies, learning about PoH and other consensus mechanisms can be a valuable skill set. The Blockchain Council offers certification courses in Blockchain and consensus mechanisms, which can provide a strong foundation for a career in this emerging field. Check them out now!