class OpenSSL::HMAC

#=> "\xDE|\x9B\x85\xB8\xB7\x8A\xA6\xBC\x8Az6\xF7\n\x90p\x1C\x9D\xB4\xD9"
hmac = OpenSSL::HMAC.digest('SHA1', key, data)

data = 'The quick brown fox jumps over the lazy dog'
key = 'key'
=== Example

the algorithm name or an instance of OpenSSL::Digest.
specifies the digest algorithm to use. This may be a String representing
Returns the authentication code as a binary string. The _digest_ parameter

HMAC.digest(digest, key, data) -> aString
:call-seq:

def digest(digest, key, data)
 hmac = new(key, digest)
 hmac << data
 hmac.digest
end unless method_defined?(:digest) # JRuby