SHA (Secure Hash Algorithm) is a family of cryptographic hash functions designed to ensure data integrity. Developed by the National Security Agency (NSA) and published by the National Institute of Standards and Technology (NIST), SHA algorithms take an input (such as a file or message) and produce a fixed-size hash value or digest. This digest is unique to the input data; even small changes to the input result in a significantly different hash. SHA is widely used in digital signatures, password storage, and data verification. Common versions include SHA-1, SHA-2, and SHA-3, each offering varying levels of security. SHA helps detect accidental or intentional data alterations.