Currently, there are four major types of e-voting around the world that are worth keeping an eye on: Brazil’s homegrown direct recording electronic (DRE) setup, Australia’s open-source software, Estonia’s Internet voting, and a Spanish startup’s efforts to expand what’s been called “crypto-voting.” Each of these approaches has its own unique set of problems, but the primary obstacles they present for many voting officials and computer scientists is their lack of ability to verify source code and expense.