A 160-bit hash function, mandated by the National Institute for Standards Technology (NIST), with security mechanisms similar to MD5. SHA-1 is defined by the United States Government in FIPS 180-1. It is a mechanism to reduce a lengthy text message to a short digest of 160 bits that is both one-way (i.e. non-reversible) and not susceptible to collisions from multiple different texts. Because SHA generates a 160-bit hash (message digest) it is much safer from brute-force cryptographic attacks than MD5. Digests are best thought of as the digital fingerprint of a message. It is a relatively fast, low-overhead and secure algorithm. SHA-1 can be used to support integrity protection (by itself), or for non-repudiation (in conjunction with public key encryption). The SHA-1 Message Digest Algorithm is described in Appendix II.