ESP32 implementation

[hadmut]

Hi,
that's not a bug report, that's just a christmas wish.

Tang servers usually suffer from two particular problems:

• they are running on regular machines with regular operating systems and usually other tasks, and such can be hacked even if the tang server itself is hacked.

• tang runs on a regular computer, and if an encrypted machine with a clevis client is stolen, probability is high that both machines are stolen together, and since the machine with the tang server tends to boot independently for bootstrapping the net, a thief/spy can resemble the network with stolen devices and make them boot and decrypt their disks / recover the key.

Therefore, would be nice to have tang running on an ESP32 microcontroller. There's extremely small modules available that can easily be hidden anywhere, where 5V or 3.3V are available, and connect to the router through Wifi, making it much more difficult to spot and steal them.

ESP32 controllers do have a bunch of security and crypto features, and seem to be a good base for this kind of task.