Code and data sharing is an important issue in Java Card. The Java Card 2.2 introduced an object sharing scheme to allow client applets to access to the server applet methods using a sharable interface object. This method suffers from some security problems such as Applet Identifier impersonation. For solving those problems, we propose two secure object sharing schemes based on the delegate model introduced by Montgomery and Krishna. Our schemes have some significant improvement over the original model in that a client applet in our system needs only one key.