Short for ‘Secure Hash Algorithm 256-bit’, SHA-256 is a cryptographic hash function that plays a crucial role in blockchain and the cryptocurrency space. It’s part of the SHA-2 family of algorithms, which were designed by the United States National Security Agency (NSA) and first published in 2001.
Designed to be collision-resistant, meaning it is computationally infeasible to find two different inputs that produce the same hash, SHA-256 produces a fixed-size, 256-bit (32-byte) hash value from an input of any size and is used to generate unique identifiers (hashes) for blocks in the blockchain, ensuring data integrity and consistency. Each block in a blockchain contains a hash of the previous block, forming a chain. This linkage ensures that any alteration in a block would change its hash, breaking the chain and making tampering detectable.
In Proof of Work (PoW) consensus mechanisms (e.g., Bitcoin), miners compete to solve cryptographic puzzles that require finding a specific input (called a nonce) that, when hashed with the block’s header, results in a hash value that meets certain requirements (e.g., a certain number of leading zeros). SHA-256 is used to generate these hashes, securing the network by making it computationally expensive to alter the blockchain.
This ensures that once a transaction is recorded in a block, it cannot be altered without changing the block’s hash, thereby maintaining the integrity and security of transaction data. Additionally, cryptocurrency wallet addresses are derived from public keys using SHA-256 (along with other hash functions).
