SHA ([SHA]) is the Secure Hash Algorithm, a standard from NIST, the U.S. National Institute for Standards and Technology, which is used in DSA(5). The standard detailing SHA is [SHS].
For a description of SHA and its security, see [AC2].
[SHS] National Institute of standards and Technology, NIST FIPS PUB 180, Secure Hash Standard, U.S. Department of Commerce, May 1993.
[AC2] Bruce Schneier, Applied Cryptography: Protocols, Algorithms and Source Code in C, second edition, John Wiley and Sons, 1996.