Public Key
The problem with technology strong enough for crypto-geeks is, only crypto-geeks will want to use it. I complained about this before, here. In response I got introduced to keybase.io... which is not the answer to this problem for your mom. Just look at it.
mouseover text: I guess I should be signing stuff, but I've never been sure what to sign. Maybe if I post my private key, I can crowdsource my decisions about what to sign.