Hash functions are one of the cornerstones of blockchain technology. They are mathematical algorithms that transform input data of any length into a fixed-length string — a hash. Even the slightest change in the input data completely alters the hash, making any forgery easy to detect.
In blockchain, hash functions perform several critically important tasks:
Block identification: each block has its own hash, which depends on the data inside the block and the hash of the previous block. This ensures the integrity of the chain.
Integrity verification: changing even a single character in the data of a block results in a new hash, making the entire chain invalid.
Proof of Work: in the PoW consensus algorithm, hash functions are used for mining blocks by finding a value that meets specified conditions (for example, the hash must start with a certain number of zeros).
The most popular hash function in blockchain is SHA-256. It is used, for example, in the Bitcoin network.
Without reliable hash functions, the idea of blockchain as a decentralized, secure, and transparent data repository simply would not work.