Mobile browsers&#x2F;devices handle client certs better than any desktop I&#x27;ve seen.  Especially since they have hw trusted storage.<p>The issue is identity&#x2F;linkage.  If they let you set up an arbitrary number of keys, so you could do one per site, that&#x27;s fine (and really, if you use the same username everywhere it&#x27;s sort of the same thing)