Another (shorter length) OTP implementation:<p>Perfect Paper Passwords: <a href="https://www.grc.com/ppp" rel="nofollow">https://www.grc.com/ppp</a><p>I've created a v3 compatible Ruby implementation of this for use in webapps etc: <a href="http://gist.github.com/74551" rel="nofollow">http://gist.github.com/74551</a>