Suppose I have a set of computers with variegate level of trust (for example):
- I fully trust my own desktop pc at home
- I trust a bit also my smartphone, but I know it could be stolen
- I trust a bit also our "family laptop" where a login exists for me, one for my wife and one for each of my daughters
- I don't trust so much the working laptop at office, since I've no control on the operating system
I have to use OTR chats and mail encryption/decriptions/signing on all these machines, but since I don't fully trust all of them, I don't want to store copies of my private key in them. I could use a smartcard but at office I can't plug it in and I cannot use it with the smartphone.
The simplest solution that I can think of, is to create a different key pair for each machine/account and share them to my buddies so that, if a machine is compromised all the others keys are still usable. However is is a pain for my buddies and complicate my chances to build a solid web of trust.
Is there any better alternative?