(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).
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.