A quick and simple javacard applet that helps demonstrating the behaviour of some smart cards. It targets ISO/IEC 7816 command cases 1 to 4.

4 generic instructions are defined:

• INS=C1 handles the incoming command as a command case 1 (no Lc, no Le)
• INS=C2 handles the incoming command as a command case 2 (no Lc, with Le)
• INS=C3 handles the incoming command as a command case 3 (with Lc, no Le)
• INS=C4 handles the incoming command as a command case 4 (with Lc and Le)

They aim at remembering the incoming APDU buffer, Lc and Le values for further use. They won't do anything more. Instructions C2 and C4 send back the APDU buffer content in the UDR field.

3 dedicated instructions are also defined as command case 2 commands:

• INS=CB retrieves the last stored APDU buffer content
• INS=CC retrieves the last value of Lc field
• INS=CE retrieves the last value of Le field

A last instruction is defined as a command case 2 command:

• INS=C5 returns the value of the transmission protocol T in use

This applet can be used with the LINQPad script defined in this gist (this is my test case).

• IDE used: JCIDE
• The applet can also be built using Apache ant
• Minimum Java Card version: 2.1.2
• Applet AID: F0 01 02 03 04 05 (because why not?)