(Bloomberg Opinion) — Finding a place to stash the keys to your cryptocurrency hoard has never been easier, thanks to options that run from putting them in a retired Swiss nuclear bunker to the humdrum use of digital-asset exchanges. It’s also never been harder to keep them safe from thieves.

Cold storage — using physical offline devices such as hard drives, safe-deposit boxes or USB sticks — is the gold standard in crypto security. To transfer Bitcoin or similar from your electronic wallet, you need to know the string of random words that makes up its de facto password, known as a seed phrase. And rather than write them down or keep them somewhere digital that’s connected to the internet, you store them in a place hackers…