SHA-256 is a cryptographic hash function that is widely used in the blockchain and cryptocurrency industries. It was designed by the [[United States of America (USA)]] [[National Security Agency (NSA)]] and is part of the SHA-2 family of hash functions. Key characteristics of SHA-256 include: 1. Input and Output Size: SHA-256 takes an input message of any length and produces a 256-bit (32-byte) fixed-size output, known as a hash value or message digest. 2. Determinism: For a given input, SHA-256 will always produce the same output hash value. This property is crucial for the integrity and security of blockchain transactions. 3. One-Way Function: It is computationally infeasible to derive the original input from the output hash value. This makes SHA-256 a strong one-way cryptographic function. 4. Collision Resistance: It is extremely unlikely for two different input messages to produce the same SHA-256 hash value. This property helps prevent potential attacks and ensures the uniqueness of each transaction. 5. Mining and [[Proof of Work (PoW)]]: In the context of #blockchain and #cryptocurrency, SHA-256 is often used as the underlying hash function for the proof-of-work consensus mechanism. Miners compete to solve the computationally intensive SHA-256 hash problem to validate transactions and add new blocks to the blockchain. The widespread adoption of SHA-256 in the cryptocurrency industry is due to its strong security properties, which help maintain the integrity and immutability of the blockchain. As a result, SHA-256 has become a fundamental component of many popular cryptocurrencies, such as [[Bitcoin]], [[Bitcoin Cash]], and others.