Ok, is there anything that you think people need in order to confirm that this actually does what it says? Smartcards are not tamper-proof (nothing probably is), they are tamper resistant, but the cost of extracting a key from the smartcard might exceed the balance of said key.

If you're talking about the actual protocol used to move the key between cards, I can detail that as well. It's nothing fancy (you can't do very fancy stuff in JavaCard ). It's plain ECDH to negotiate a session key (each party verifies the other's public key first) and AES to encrypt the private key with the session key. Feel free to ask if you need me to go into details.