What is SHA-256?

SHA-256 (Secure Hash Algorithm 256-bit) is a cryptographic hash function designed by the United States National Security Agency (NSA) and published by NIST in 2001 as part of the SHA-2 family. It takes an input of arbitrary length and produces a fixed 256-bit (32-byte) hash value, represented as a 64-character hexadecimal string. The algorithm processes data in 512-bit blocks through 64 rounds of bitwise operations, modular additions, and compression functions, making it computationally straightforward but practically impossible to reverse-engineer the original input from the output.

SHA-256 is widely regarded as one of the most secure and thoroughly vetted hash functions in use today. It provides strong collision resistance, meaning it is computationally infeasible to find two different inputs that produce the same hash output. The algorithm is highly efficient on modern processors and benefits enormously from parallel computation, which makes it exceptionally well-suited for ASIC implementation. This has led to a highly specialized mining industry where purpose-built ASIC machines dominate, making GPU or CPU mining of SHA-256 coins economically unviable.

SHA-256 was chosen by Satoshi Nakamoto as the proof-of-work algorithm for Bitcoin, the first and most valuable cryptocurrency, launched in January 2009. This choice established SHA-256 as the foundational mining algorithm of the entire cryptocurrency industry. Beyond Bitcoin, SHA-256 is used by many major cryptocurrencies including Bitcoin Cash, Bitcoin SV, and Peercoin. It is also used extensively outside of cryptocurrency in SSL/TLS certificates, digital signatures, and data integrity verification across virtually all modern computing systems.