Uncaught exception 'Phalcon\Crypt\Exception' with message 'Size of key is too large for this algorithm' in phalcon/crypt.zep:320 Stack trace
https://stackoverflow.com/questions/27935592/mcrypt-decrypt-size-of-key-is-too-large-for
hope that helps.
basically in your bootstrap/config file where you register the crypt service put 8 chars as a key
To ask about Base64 results if you remove the slash? ('/') because he will affect the parsing of the URL