Cryptographic Hash Function

A cryptographic hash function is an algorithm that maps an input of arbitrary length to a fixed-size output, called a digest, such that the mapping is deterministic, fast to compute, effectively irreversible (preimage resistant), and collision resistant, meaning it is computationally infeasible to find two different inputs producing the same digest. The SHA-2 and SHA-3 families, MD5, SHA-1, RIPEMD and BLAKE2 are widely cited members of this class, used for data integrity checks, digital signatures and password storage schemes. MD5 and SHA-1 are now considered cryptographically broken against collision attacks and are retained mainly for legacy compatibility rather than new security-critical use.