(SHA) A hashing algorithm that generates a message digest. SHA is used with the Digital Signature Algorithm (DSA) in the Digital Signature Standard (DSS), among other places. CryptoAPI references this algorithm by the algorithm's identifier (CALG_SHA), name (SHA), and class (ALG_CLASS_HASH). There are four varieties of SHA: SHA-1, SHA-256, SHA-384, and SHA-512. SHA-1 generates a 160-bit message digest. SHA-256, SHA-384, and SHA-512 generate 256-bit, 384-bit, and 512-bit message digests, respectively. SHA was developed by the National Institute of Standards and Technology (NIST) and by the National Security Agency (NSA).

The current approved hash algorithm produces a message digest of 160 bits.

An algorithm that assures data integrity by generating a 160-bit cryptographic message digest value from given data. If as little as a single bit in the data is modified, the Secure Hash Algorithm checksum for the data changes. Forgery of a given data set in a way that will cause the Secure Hash Algorithm to generate the same result as that for the original data is considered ccomputationally infeasible. An algorithm that takes a message of less than 264 bits in length and produces a 160-bit message digest. The algorithm is slightly slower than MD5, but the larger message digest makes it more secure against brute-force collision and inversion attacks.