>ok, only objects that are serializable can be added to the rmiregistry right?
This I don't know about. I know they must be Remote, but you could be right.
>That means that If would like to make a class that uses Cipher I cannot add it
>to the rmiregistry since I cannot serialize Cipher.
You will have to take care to customize your (de)serialization for your class. Read more in the java.io.Serializable javadoc.
> ok, only objects that are serializable can be added
> to the rmiregistry right?
No, only classes that implement Remote. Serialization has nothing to do with it. I think there is some confusion here. The RMI Registry is a naming service for exported RMI objects. Serialization is used to transport arguments and results between exported RMI objects.