I wonder what the reasonable balance between reuse and over exposure is; I'd think you would want less keys per device, and have less key overlap (ie more keys overall.) But forty two sounds high, and isn't it now just 42x more at risk?

> I would argue reusing private keys worldwide is slapdash engineering

I wasn't suggesting it, and frankly can't see how that could be a solution in this instance. I was making a comparison against current practices on a harder problem to solve , i.e. safely scaling a single private key in an SSL certificate across many servers is solved today without a 1:1 server to certification ratio