Yes, the private keys are stored only on the secure device, but that wasn't my question. My question was, if the client can create the required unsigned transaction, which requires nothing more than knowledge of the public block chain, why does the secure device need any more data than just that unsigned transaction, which it then signs. Everything but the actual transaction signature is public knowledge, the only thing the device needs is the transaction itself, so that it can properly sign it. It does not need to know all other unrelated transactions that I've done in the past, and it has no way of knowing whether to trust them anyway.
If the device does all of the wallet stuff itself, you can take it on the road.
I want this thing to be my wallet. Not a glorified dongle that allows me access to the wallet stored on my PC.
The only reason I can think of that you wouldn't want an untrusted client preparing the unsigned transaction for you is that you don't want to divulge any of your public keys that are holding money. But that means that if you receive money away from your trusted machine, you won't be able to spend that money. I think a combination makes sense. You can download a cache of your current transactions at home. When on the road, if these transactions can cover the bill, you don't need to divulge any public keys. Otherwise you have the choice of divulging public keys to the client to check for new incoming transactions until you can cover the bill.
I'll release the link to my website as soon as the lightweight client is ready for testing.
Looking forward to it
