Examples of Proof of History in Blockchain Solutions

There have been significant changes in the blockchain scene since the inception of Bitcoin in 2009. Currently in use, there are several blockchain networks, each with unique operational methods that address historical problems.

Traditional Consensus Mechanisms:

Proof of work (PoW): PoW, Bitcoin’s main platform, relies on miners to verify transactions and consider complex mathematical problems to secure the network but the process is powerful and delivers more computing power, raising questions about its scalability and environmental impact.

Proof of Stake (PoS):  PoS is a PoW substitute that chooses validators according to the amount of coins they own. The network randomly selects validators to suggest and validate new blocks when validators stake (lock up) their currency. While this method uses less energy than proof-of-work, it might lead to centralization if a few companies own the bulk of the shares.

Introducing Proof of History (PoH):

Proof of History (PoH) is a new consensus technique deployed with Proof of Stake (PoS) on Solana, the primary blockchain of the SOL currency. The goal of this integration was to improve upon the shortcomings of the current systems and provide a blockchain solution that was quicker, safer, and more scalable.

Understanding PoH:

Conceptualized as a digital clock: PoH ensures that authenticators on the blockchain agree to the order in which transactions take place. It does this by assigning a time stamp to each segment. Unlike traditional timestamps, which rely on a central authority, PoH uses cryptography to create a verifiable record of the past.

Verifiable Delay Function (VDF): At the core of PoH is VDF, a cryptographic function that requires a certain verifiable time. This ensures that timestamps are generated at predetermined intervals, confirming the chronological sequence of events in the blockchain.

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Benefits of PoH:

Enhanced Transaction Speed: PoH makes the process of determining the transaction order more efficient. Unlike PoW, where validators compete to solve intricate puzzles, or certain PoS implementations, where they depend on selected leaders, PoH uses timestamps to predetermine the order, which speeds up transaction processing.

Improved Security:  The blockchain’s historical integrity is protected by the tamper-proof timestamps generated by Proof of Hashing. Because of the difference in timestamps, any effort to modify the order of transactions would be readily discovered. By doing this, problems like double-spending where a single digital item is spent twice are lessened.

Energy efficiency: PoH uses less energy than PoW because it relies on cryptographic functions rather than raw processing power, which requires more energy therefore PoH is a more robust alternative addressing environmental issues raised by traditional blockchain systems.

Solana’s Implementation:

Solana uses PoH through a new consensus tool called Practical Byzantine Fault Tolerance (pBFT) to achieve consensus on the validity of services.

PoH acts as the timekeeper, ensuring the accurate sequencing of events, while pBFT handles transaction agreements. Validators use the timestamps generated by PoH to verify the order of transactions before reaching consensus through pBFT.

Drawbacks of PoH:

Limited Adoption: Currently, Solana remains the primary user of PoH. While it offers potential, broader adoption across the blockchain ecosystem is yet to be seen.

Complexity for Newcomers: The underlying cryptographic nature of PoH can be challenging for individuals new to blockchain technology.

Evolving Technology: As a relatively new consensus mechanism, PoH is still under development. Time will tell how it addresses potential security concerns and gains wider acceptance.

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Comparison with Other Mechanisms:

PoH vs. PoW: PoH prioritizes time-based validation through VDFs, making it significantly more energy-efficient than PoW’s resource-intensive mining process. PoH also offers faster transaction processing times due to the streamlined approach to ordering transactions.

PoH vs. PoS: Unlike PoS, which relies on coin stakes for validator selection, PoH utilizes timestamps for establishing the order of events. This distinction can potentially lead to a more decentralized network in PoH as validator selection is not solely determined by coin holdings.

The future of PoH:

PoH presents a hopeful view in terms of energy efficiency, speed, and security, but its long-term survival depends on widespread acceptance and further development.


Proof of History (PoH) represents an innovative consensus mechanism in the blockchain realm. Its emphasis on verified timestamps opens the door for blockchain solutions that are quicker, more secure, and more scalable. PoH can completely change how we use and interact with blockchain technology as it develops and becomes more popular.

What are the technical details of verifiable delay functions (VDFs)?

VDFs are cryptographic functions that are obviously slow to create but can be verified quickly. This means that one can easily confirm that a certain time has elapsed based on the results of the VDF. In PoH, the validators run the VDF repeatedly, generating timestamps based on the completion of each iteration.

How is PoH integrated with other consensus methods such as pBFT in Solana?

Although PoH establishes the sequence of events through timestamps, it does not directly determine the legitimacy of the transaction. Solana uses a Byzantine fault tolerance (BFT) algorithm called pBFT to obtain a consensus on a case itself. Validators use the timestamps provided by the PoH before agreement on their validity via pBFT to ensure that the transaction occurred in order.

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Can PoH be vulnerable to attack?

As with any new technology, PoH is still in development and can have potential security vulnerabilities. One theoretical concern is Deial-of-Service (DoS) attacks where a malicious actor attempts to disrupt the network by computing more than authenticators Ongoing research focuses on fixing perceived vulnerabilities thus improving the security of PoH services.

What is PoH that can be used beyond cryptocurrencies?

The basic PoH concept of creating verifiable time currencies has applications that extend beyond the realm of cryptocurrencies. Possible applications include:

  • Supply chain management: Time stamps ensure data consistency and transparency by tracking content in the supply chain.
  • Secure Audit: Various invariant PoH timestamps can be used for secure audit trails across projects.
  • Data source: PoH can be used to identify the source and ownership of digital assets, ensure authenticity, and prevent unauthorized alterations.

By understanding the basic principles of PoH, its benefits and limitations, and its potential applications, individuals can gain valuable insight into the evolving blockchain technology.