RosettaCodeData/Task/SHA-1/00DESCRIPTION

'''SHA-1''' or '''SHA1''' is a one-way hash function;
it computes a 160-bit message digest.
SHA-1 often appears in security protocols; for example,
many HTTPS websites use RSA with SHA-1 to secure their connections.
BitTorrent uses SHA-1 to verify downloads.
Git and Mercurial use SHA-1 digests to identify commits.

A US government standard, [[SHA-1/FIPS-180-1|FIPS 180-1]], defines SHA-1.

Find the SHA-1 message digest for a string of [[octet]]s. You may either call a SHA-1 library, or implement SHA-1 in your language. Both approaches interest Rosetta Code.

{{alertbox|lightgray|'''Warning:''' SHA-1 has [https://en.wikinews.org/wiki/Chinese_researchers_crack_major_U.S._government_algorithm_used_in_digital_signatures known weaknesses]. Theoretical attacks may find a collision after [http://lwn.net/Articles/337745/ 2<sup>52</sup> operations], or perhaps fewer.
This is much faster than a brute force attack of 2<sup>80</sup> operations. USgovernment [http://csrc.nist.gov/groups/ST/hash/statement.html deprecated SHA-1].
For production-grade cryptography, users may consider a stronger alternative, such as SHA-256 (from the SHA-2 family) or the upcoming SHA-3.}}