Consensus algorithms are mechanisms for securing blockchains and cryptocurrencies. Different cryptocurrencies and blockchain networks use different consensus algorithms., each of which has its own advantages and disadvantages. By the way, most cryptocurrencies use more common consensus algorithms like proof of work and (different versions of) proof of stake. A few of them use rare algorithms, and Solana is one of them. Solana uses a consensus algorithm called proof of history. Stay with us in this article to figure out what proof of history is and how it works.

What is proof of history?

The centralized world is highly reliant on the concept of trust. The expansion of the Internet and different industries moving toward digitalization led to a system NOT reliant on trust. The concept of “timestamp” had a key role in eliminating the need for trust. Timestamp was first introduced by Satoshi Nakamoto and used in the Bitcoin blockchain. It lets us store all data on the public ledger in an anonymous, unchangeable, and decentralized way. The idea behind timestamp is simple: creating a fingerprint for each piece of data, using information like the data’s title, its time, and whatever it includes. This unique fingerprint is saved as a hash. Therefore, any change in the input changes the hash in an unpredictable way. Timestamp determines the exact time of validating and mining a transaction in a blockchain. It shows the time sequence of blocks based on the UTC time or the Unix Time. It prevents the further manipulation of data this way since prevents repeated transactions and blocks.

Proof of history is a consensus algorithm that proves an event has happened before another specific event and after another specific event without using a timestamp. It was first used by the Solana blockchain. If you want to know how proof of history works, stay with us in the next part.

How does proof of history work?

In proof of history, the blockchain consists of a sequence, and each sequence has a state. This state is revealed using the hash function. The starting value of a proof-of-work network is random. The hash of this starting point is calculated using hash functions and cryptographic methods. Then this hash is used as the input and is given to the same function again. This sequence can continue to number N, and the hash N finally represents the actual output. Proof of work is designed in a way that only one computer can calculate a sequence of hashes. Since calculating hash N is practically impossible without calculating the previous hashes, this hash reveals that some real time has passed and the hash has actually been calculated. Proof of work reveals the number of times a hash function has been called and the passage of time between two events.

The origin of proof of history

As we previously mentioned, Solana was the first blockchain to use proof of history, and it is still the most famous blockchain using this algorithm. Solana is now the most scalable first-layer blockchain. It has combined proof of history with proof of stake and has developed a unique consensus algorithm. Using proof of history in combination with proof of stake is a reason for Solana’s high scalability while staying safe and decentralized.


Proof of history has proved to have a high potential. Of course, this consensus algorithm has its own disadvantages (like all other rivals). For example, its biggest disadvantage is that it consumes a large amount of computational power. By the way, it has been fairly successful up to now, and much of this success can be seen in the success of Solana. Solana has had a significant price growth in its lifetime and it is hosting more and more decentralized applications every day. Only time will tell if other blockchains will decide to use proof of history or not.

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