Problem Statement

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, FIPS 180-1, defines SHA-1. Find the SHA-1 message digest for a string of octets. You may either call a SHA-1 library, or implement SHA-1 in your language. Both approaches interest Rosetta Code.

Let's start with the solution:

require "openssl"
puts OpenSSL::Digest.new("sha1").update("Rosetta Code")