A controversial blockchain-based mobile voting app called Voatz is getting put to the test again.

The city of Denver revealed today that it has agreed to implement a mobile voting pilot in its May municipal election using the four-year-old, Boston-based startup’s technology. It will be offered exclusively to active-duty military, their eligible dependants and overseas voters using their smartphones.

All were notified that they can use Voatz via a newsletter this morning, along with a link to sign up to participate if they so choose.

Voatz — which had raised $2.2 million in funding led by the venture arm of Overstock.com last year — says it has conducted more than 30 successful pilots already. Two of these in West Virginia attracted the financial backing of Tusk Philanthropies, the philanthropic operation of investor, operator and strategist Bradley Tusk, who was featured last year in The New Yorker for his involvement in both efforts.

One was a small pilot project in West Virginia that gave overseas citizens and members of the military stationed abroad access to Voatz to cast ballots on their phones, though it was open only to residents of two counties. The technology was put to the test again in last November’s mid-term elections, in which nearly 150 people voted from 24 out of the state’s 55 counties.

We talked with Tusk in early December about both efforts and about Voatz more generally, which Tusk hasn’t funded but whose mission of enabling more people to vote, more easily, he aggressively advocates. Though mobile voting, blockchain-based apps and Voatz in particular have been criticized as potentially vulnerable to hacking, Tusk spent the first 20 years of his career in politics, and in his view, unless more people are empowered to “advocate politically” from their phones, politicians will continue to respond to the far smaller number of voters who actually show up at the polls.

Tusk also believes Voatz works, having hired outside examiners to assess the first West Virginia pilot, including Andre McGregor, a former FBI cyber special agent who is now the global head of security for TLDR, a company that specializes in blockchain technology. It may explain why, in partnering with the city of Denver and the National Cybersecurity Center, a non-profit organization that was originally created as an office within the U.S. Department of Homeland Security 11 years ago, Tusk Philanthropies again invited Voatz as a partner in Denver’s mobile voting endeavor. (A spokesperson for Tusk Philanthropies tells us that Colorado has also explored developing an open-source mobile voting platform but that it simply doesn’t exist yet.)

Certainly, it’s conceivable that Voatz is no less secure than existing options for overseas military personnel, who often submit their votes via email. With Voatz, ballots are transmitted between up to 32 “permissioned” computers that have to agree algorithmically that a ballot is legitimate before it gets recorded and counted, and this only after a voter has been identified through numerous other steps. Among these: a voter must provide a phone number and an eight-digit pin and submit a photo of his or her driver’s license. The voter must then they shoot and submit a video of their face, which is then processed by facial recognition technology that can confirm (or not confirm) that the face in the video belongs to the same person registered as a state voter.

To assuage any lingering concerns, the city of Denver will additionally conduct its own audit. Meanwhile, Tusk Philanthropies will work with a cybersecurity partner ShiftState to conduct an independent audit, in addition to the internal audit done by of Voatz.

The city of Denver says that 4,000 international voters are eligible to use the app.

Interestingly, despite the efficiencies Voatz promises, the voting process still won’t be an easy one. Fully 65 candidates have tossed their hats in the ring for public offices, according go the region’s city magazine, 5280. And while far-flung military personnel may be using a blockchain-based app, the placement of each mayoral candidate on the ballot will be determined in decidedly old-school fashion — by drawing their names out of a bingo-ball turner.