Hash functions are algorithms that map data of arbitrary size to a fixed-size output, with cryptographic hash functions designed to be one-way and collision resistant. They are central to security and blockchains.
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- A hash function takes an input of any length and produces a fixed-length digest. Cryptographic hash functions are designed so that it is infeasible to reverse the output or to find two inputs with the same digest.
- Hash functions underpin digital signatures, data integrity checks, password storage, and the linking of blocks in a blockchain. The SHA-256 function, for example, is used in Bitcoin’s proof of work and block structure.