Bitcoin has recently passed the $1000 mark, raising another round of speculation on the crypto-currency’s future legitimacy, but it’s not the only digital currency in circulation, and Samuel Gibbs at Business Insider goes over a few that are trying to supplant Bitcoin as the future of online payments. Even if most of them are destined to fade away, past technological shifts tell us that Bitcoin’s position as the top digital currency is far from guaranteed. Bitcoin transactions Conceptually, bitcoin works because transactions and the creation of new currency are both handled by solving hard mathematical problems. In order to cheat…