I don't follow this - the software must necessarily run on some hardware, so while the software may be provably secure that doesn't help if an attacker can just pull key material off the bus?
> "This system is unhackable, if the user doesn't do the thing that hacks it" is not very useful.
It's the best you're gonna get, bud. Nothing's "unhackable"—you just gotta make "the thing that hacks it" hard to do.