gen_random_urandom

# File lib/securerandom.rb, line 97
    def gen_random_urandom(n)
      ret = Random.urandom(n)
      unless ret
        raise NotImplementedError, "No random device"
      end
      unless ret.length == n
        raise NotImplementedError, "Unexpected partial read from random device: only #{ret.length} for #{n} bytes"
      end
      ret
    end