The URI you submitted has disallowed characters. Endoded url

[eluser]others20[/eluser]
I have a registration form in my application. When someone complete the registration receive an email with a link to confirm registration (typical situation).

The link is something like this

http://www.myDomain.com/registration/val...8ArjFET/8Q==

registration is the controller

validation is the function

and the last one is the username

I did the username encode...

Code:

$encrypted_username = $this->encrypt->encode($username);

when I go to this link i get this error

The URI you submitted has disallowed characters.

If I change my config.php line code to

Code:

$config['permitted_uri_chars'] = '';

everything goes right, but they say we shouldn't do this.

So, how can I solve this problem right?

[eluser]others20[/eluser]
I changed my config.php to

Code:

$config['permitted_uri_chars'] = '+=\a-z 0-9~%.:_-';

and now is working fine, I hope this is a safe solution.