The Secure Hash Algorithm 1 ( SHA1 ) has been officially adopted by the United States government as the Secure Hash Standard of the Federal Information Processing Standard ( FIPS ) and is specified in RFC 3174. See also FIPS 180-1. SHA1 uses a 160 bit digest which is designed to replace earlier 128 bit message digests such as MD5. Successful attacks on the latter have been demonstrated in cryptographic literature.
Potential users of SHA1 are adivsed that in contrast to RIPEMD-160 the design criteria as well as an earlier attack on the SHA-1 algorithm are generally held to be secret. The use of RIPEMD-160 is therefore recommended over the use of SHA-1.