Have you considered adding support for a generic trusted path protocol so any server can send a message and get back an A/B answer in a secure manner?
Do you have any proposal how this should work? Actually device is able to sign bitcoin transactions (pay to address, pay to script hash) and sign bitcoin messages.
Yes. Consider the case of online voting. The voting server wants to ensure the following
a) The vote is cast by a human, not a virus.
b) The vote is cast by each human only once.
We can satisfy this use case by using Trezor like this:
- Each Trezor has a unique public key (can be RSA) and a certificate signed by the manufacturers, ie, you and stick.
- When you start the voting process, the Trezor sends its certificate to the computer, which then sends it on to the voting server.
- The server checks that this certificate has not been seen before, and then encrypts/signs a protocol buffer that includes a message to display onscreen (any arbitrary text) and the two options available. That signed message gets sent to the Trezor, which shows it on screen.
- The users answer is then signed with the devices private key and uploaded to the voting server which checks it against the public key in the certificate.
In this way, the server can know that no virus interfered with the communication and there is no fake device at work. Of course, it assumes that the devices are somewhat secure against physical tampering.
If you can already sign/verify text messages in the standard way, then I guess you could add it on top of that, though the need to communicate certificates and things makes it not really necessary to re-use something designed only for text.
You don't have to do this now. As the software is open source, somebody could contribute such a protocol and then you incorporate it into your signed builds.
