Hey EyeHawk, I need to use RC4 as well for a project, because it's reversible encryption and there are versions for PHP and ActionScript which makes it very handy for cross platform games.
It would be great if you could add RC4 functionality to your plugin. I could send you the JS RC4 encrypt/decrypt functions.
The output is binary, which is a hassle if you need to use it in a URL for example, so what I normally do in PHP is use PHP's pack() and unpack() functions to convert it to hex
For example
unpack("H*0", rc4crypt::encrypt($password, $string));
returns something like
319d4323fed9d324436fc1d137884a92cc00aefc0eeccf0f01da95ee1b7087aac69c11250b7540a509b7705b3409c8b4178edbbce5
Which is a lot easier to use.
Then at the other end you'd use PHP's pack() function to return it to it's original form:
pack("H*", $encryptedstring);
I think there's a pack() function for JavaScript but no unpack() function. The source of PHP's unpack() function is available so it should be straightforward to convert to JS. So if you were to add RC4 encryption you could also add options to convert to and from hex.
Cheers
Lucas