You have a device already?
This #nostr note is posted from a small test application and signed with a key that is internal to the #security device.
Ironically, I have no access to this key, which is deterministically generated within the device, so with the next changes to the firmware-binary I'm going to lose access to this key, .. at least when I use the updated program-binary.
There are multiple modes of operation. nostr:nevent1qqs99ehnglvqm7zjp4jt0g2x803s3sl0cxc5ejlrgps0jxqrlx4d0yspz4mhxue69uhhyetvv9ujuerpd46hxtnfduhsygz2plnksne0pxs73kj6a4q03a044z4ncpunun8eg4ryjl233jpwsvpsgqqqqqqs4lrtxf
Discussion
You can buy a general purpose "security device", currently a sort of early experiment, IIUC. (See https://tillitis.se/ ) It can load small programs. I'm writing such a program.
I'm not claiming this device is perfect, but it allows for many solutions like this one. (I'm not associated with them. Just playing around with the device.)