Proof of History is the consensus algorithm devised by the developers of Solana (SOL), and is only used by this blockchain to date.
Proof of History ensures that time is saved by placing certain events in a sequence. Imagine taking a picture of the newspaper that fell on your doormat today. This picture is proof that the picture was taken after this version was published. After all, it is impossible to take a picture of this newspaper if the newspaper has not actually been published yet.
Another example is if you’re at a football game, and you take a picture. This picture is proof that the it was taken during the football game. It is impossible to take a picture of the same football match before or after the fact, because it has not yet started or has not yet ended.
This is the way Proof of History works. However, this consensus mechanism does not take pictures of events. Instead, a specific hash is used. This hash is based on past events, making it impossible for the hash to have developed before or after this event.
Verifiable Delay Function
Proof of History is in fact a Verifiable Delay Function, which is not a new concept in the IT world. A Verifiable Delay Function needs a certain number of numbers and events that have happened before. Based on this, an output is created by means of the SHA256 hashing algorithm. This output is public, and can be verified by anyone. This allows an entire network of nodes to check whether the outcome of the Verifiable Delay Function is correct, and whether a node is also performing its work correctly.
Solana’s blockchain can process more than 60,000 transactions per second. This is a very large number, especially when compared to Ethereum, which can process less than 20 transactions per second. That’s why many people refer to Solana as the Ethereum killer.
The high scalability of Solana is mainly due to the Proof of History mechanism, but of course also to the other techniques and protocols developed by the team behind Solana. Think, for example, of Sealevel and Turbine.