<a href="https://tweetnacl.cr.yp.to" rel="nofollow">https://tweetnacl.cr.yp.to</a><p>TweetNaCl, with two versions on that page. There have been ports to other languages.
Are you possibly thinking of libhydrogen?<p><a href="https://github.com/jedisct1/libhydrogen" rel="nofollow">https://github.com/jedisct1/libhydrogen</a>