Over the last few years, so-called "crypto-currencies" – digital equivalents of a monetary exchange unit, have been all the rage. The most well-known in the category, Bitcoin, has had quite a run.
Starting out as a "virtual penny stock" it rose in 2014 to the elevated height of $1,150, before crashing back to earth. This "electronic currency" is created and stored in a computerized "wallet." Purchases and sales are made via a "blockchain" which keeps a memory of every transaction conducted. Private keys (supposedly) provide assurance that a Bitcoin holder’s account is safe.