EllisLab/CodeIgniter — pull request #1873 by lysenkobv (2012-10-10 17:11:49+00:00)
Title: libraries/Encrypt.php decode improvement

if base64 string is NO valid the result of decoded string is something like this "23Y�����������S�� �����i��!q"
(base64_encode(base64_decode($string)) !== $string) check is this base64 string valid