EyeHawk: Well I don't know RC4 even by name, and apparently, the MD5 and SHA- algorythms stand in the "defined" character set, so no problem with the encryption while I was working on them.
I guess it depends on how you include the algorythm in your plugin.
At worse, I'd advice to have an array containing the "character set" and work from there, though it might get pretty complicated.