Bitcoin-like currency system for prison

Charlie Shrem, founder of the Bitcoin Foundation, is going to federal prison for a couple of years. He wonders if something like bitcoin could work behind bars.

Many different types of prison currency, from stamps to cigarettes, have existed over the years. After prisons began banning smoking a decade ago—it was banned in all federal prisons in 2014—prisoners started exchanging tins of mackerel due to their long shelf live and high protein, which is lacking in prison. Laundry may cost 1 mack, a haircut 2 mack, and a personal trainer can run you 25 mack a month. So why not Bitcoin?

As it turns out, running a Bitcoin system in prison is illegal—the Bureau of Prisons strictly forbids "possession of money or currency, unless specifically authorized"—but it's still a fun thought experiment. Bitcoin is primarily used over the internet, but does it need to be?