The functionality of file transfer from FS-Applet to IH-Applet has been realized by exploiting the APDU protocol (Application Protocol Data Unit) (Deville et al.
In particular, CLA (having size of 1 byte) specifies a class of commands (as defined by ISO 7816-4), INS (1 byte) denotes the particular command inside this class, P1 (1 byte) and P2 (1 byte) are the parameters of the command, Lc (1 byte) denotes the size of the following DATA field, DATA contains data to be sent to the smart/Java card, and finally Le (1 byte) shows the size in bytes of the possible APDU response.
Concerning APDU response, Java card sends a response containing in the status word SW, having size of 2 bytes, a response code of 0x9000 to indicate that the file transfer completed successfully.
CAP files are processed by an off-card installer, called scripigen, another tool of Java Card'm Technology (JCDK, 2008) that produces a script file containing the sequence of APDU commands necessary to upload the applets to the Java card.
JCRMI framework allows programmers to ignore the APDU message-passing mechanism in order to focus on interfaces with Java Card applets.
Java Card technology with RMI is a framework that allows on-card programmers to implement card applets at the level of objects and methods, thus ignoring the APDU message-passing mechanism to concentrate their efforts on building Java Card applet functionality.