I study computer security at the PhD level and have an interest in key management. In the recent news we have noticed how poorly protected some private keys remain. Crackers have stolen Certificate Authority private keys and bitcoin wallets.
Hardware security modules, dedicated airgapped boxes, smart cards, etc - there are lots of solutions (and you now have something to Google). You'll get better answers if you ask more specific questions, and Google is probably a better tool than HN.
