"soft JavaCard" for Android HCE

[!NOTE] This is just an idea, maybe a student will pick it up.

Step 1. Prep

• you have a standard JavaCard applet YourApplet that replies "Hello, World!" to a simple APDU.
• you compile this into a unstripped .cap file with ant-javacard (step before CAP conversion)
• use java -jar jandroidcard.jar -install YourApplet.cap -params ... much like with GlobalPlatformPro to convert the .jar to .dex and add install manifest. You will end up with a "YourApplet.zip" file (format/contents/extension to be clarified)

Step 2. Run

• you open the "JAndroidCard" app
• it will have a single button "select applet"
  • maybe some more tunable checkboxes like "persist card data" etc
• you click it, browse to the generated YourApplet.zip file, and open it
• JAndroidCard sets up jcardsim simulator instance with the install manifest data and hooks up the defined AID-s with the system
  • https://developer.android.com/reference/android/nfc/cardemulation/CardEmulation#registerAidsForService(android.content.ComponentName,%20java.lang.String,%20java.util.List%3Cjava.lang.String%3E)
• JAndroidCard will pipe APDU-s between HCE and Simulator
• you can now tap the phone to a NFC reader to use the phone just like a JavaCard that has YourApplet installed.
  • caveats about data and applet_lifecycle==app_lifecycle, background/foreground routing etc apply.

Step 3. Profit!

• mostly for the lulz
• maybe route some crypto ops in the jcardsim JC API to Keychain etc

[!NOTE] This is not unlike https://frankmorgner.github.io/vsmartcard/ACardEmulator/README.html or https://web.archive.org/web/20240927032835/https://github.com/martinpaljak/mobiil-idkaart but the idea here is to make a single Android app and dynamically load applets into it. And the possible hooking up of the simulator to Keychain backends or other similar shenanigans.