Quote from: Mike Hearn on February 01, 2013, 01:05:56 PM

How does the "type OTP" thing work? There are only two buttons, right? I didn't really understand that part.

Trezor displays OTP on display, user re-type it to computer...

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BTW confirming each address+output might be confusing in the case of the change output. Maybe you can suppress that one?

We were thinking about this already and although I'm slighly inclining to hiding change addresses, there are still few open questions. Facts:
a) Trezor can detect change address (it can check that address has been generated from its seed).
b) Trezor has no chance to check if change address provided by the computer is sane.

The most safe solution is that Trezor will display *all* outputs, including change address. As change address can be detected, it can be marked/highlighted somehow. Problem is that user who's not aware of concept of bitcoin transactions may be confused by the fact that Trezor is signing two outputs when he typed only one outgoing address.

In the oposite, by completely hiding change addresses, some attack vectors are possible. Let's imagine hacked client which sends all coins from change addresses to BIP32 address on index 2^32, 2^32, 2^32, 2^32. Although these coins are still owned by the user, good luck finding the address used in change output...

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Just re-iterating my hope that you make the firmware split (fixed bootloader and reflashable main part), that way, when the payment protocol work is progressing it will be a smooth upgrade to have Trezors show names instead of addresses.

I'm looking forward payment protocol as well, I think it will work perfectly together with Trezor...