Keeping secrets is sacrosanct in the Vatican; in the conclave, it’s canon.

As the College of Cardinals goes behind closed doors Wednesday in Vatican City for the papal conclave, the world will have to rediscover something in short supply in 2025: patience. Only when a plume of white smoke billows (as opposed to black smoke) from the Sistine Chapel chimney will the world know: the next pontiff has been selected.

The process could last days. The conclave is held in utmost privacy, cardinals vote by secret ballot, and front-runners — the papabile — are not always victorious. All the public can do is wait.

This year, the anticipation in the United States may be higher than usual, catalyzed by Hollywood intrigue. The film “Conclave,” a political thriller starring Ralph Fiennes, won an Academy Award for best adapted screenplay and was nominated for seven others, including best picture. But for those pope watchers hungry for intel, good luck learning anything before the new pope materializes on the loggia overlooking St. Peter’s Square.

The conclave is one of the last bastions of modern political secrecy, impervious to news cycles, late-night social network flurries or clickbait scoops. It’s … comforting, somehow, to rediscover this — and it’s easy to wonder whether the tradition can withstand the instant-information age. Where else can such a consequential decision be made, a world leader be selected, a moral guidepost for a large swath of god-fearing society … and almost no one knows what happened?

James V. Grimaldi, the executive editor of National Catholic Reporter (who formerly worked at The Washington Post and the Wall Street Journal), said that the conclave proceedings aren’t unlike the elections for a speaker of the House or Senate majority leader in the U.S. Congress, where most everyone rallies around the chosen candidate — even if the winner wasn’t a voter’s first choice. But in the conclave, information about who campaigned for the papacy, which factions emerged and who voted for whom are unknown until well after the new pope emerges — and even then it can take years for reliable information to leak to in-the-know reporters.

“The thing that I love about this story is that it’s secret. If it were open to the press, we wouldn’t have a job!” Grimaldi said, laughing. “I’m on the catbird seat. I love it.”

The cardinals weren’t always proficient at keeping secrets or interested in doing so, said Miles Pattenden, a University of Oxford historian of the Catholic Church. “In every one of those 16th- and 17th-century conclaves, every Catholic prince has agents and spies and ambassadors in it,” he said. “They write letters every day.” The irony, he said, is that we actually know far more about conclaves from nearly 500 years ago than about the ones that elected modern popes.

There’s a practical reason conclaves are supposed to be conducted in private. “We’ve all read the Dan Brown novels. We’re obsessed with secrecy,” said Kurt Martens, a professor at the School of Canon Law at the Catholic University of America. “But secrecy is there for another reason. It’s not to hide things. It’s to make sure that those who elect a new pope are free of any external interference.”

There’s also a theological reason for the tight lips: The Holy Spirit is said to come down and inspire the cardinals in their deliberation, a phenomenon requiring the kind of holiness men of the cloth can find only in seclusion.

The conclave’s development occurred in two distinct phases, Pattenden said. First came isolation, beginning in 1059, when Pope Nicholas II excluded everyone except the cardinals from having a say in papal elections. The second phase — the advent of secret balloting — wasn’t fully established until 1621.

Another watershed moment happened in 1903, when Emperor Franz Joseph of Austria-Hungary vetoed a papal candidate, Martens said. Once Pope Pius X was elected, he banned the veto in 1904, and the cardinals have operated without political override ever since.

These days, influence campaigns come from the internet. “It started the moment after Pope Francis died,” Martens said. Critics weighed in on whether the next pontiff should continue Francis’s legacy or change course.

Before and during the conclave, cardinals take multiple oaths of secrecy. So do the nuns and support staff that assist the proceedings. All of these oaths carry the church’s highest penalty: excommunication.

Today’s conclaves employ sophisticated measures to protect secrecy. Philip Pullella, who has spent decades covering the Vatican for Reuters, said that the cardinals are not allowed to bring phones into the Sistine Chapel and that the building has signal-jamming equipment under the floors. Once the conclave starts, even the best-sourced Vatican reporters join the world in a papal waiting game.

The tradition of secrecy will hold during the upcoming conclave, said Pullella, adding a caveat: “If it doesn’t, it’s going to be a big scandal.”

Despite these measures, modern conclaves don’t remain completely unknown forever. Details typically emerge years later, often through books written by Vatican insiders. “For some reason, people take the promise that they made a little bit less seriously as time goes on,” Pullella said. The only person exempt from these secrecy obligations is the pope himself. Francis, for instance, didn’t violate any rules by writing about the conclaves in his autobiography, “Hope,” which was published in January.

The conclave’s elaborate secrecy serves a bigger purpose beyond theological considerations: It preserves an air of mystery that’s crucial for the self-preservation of the institution. “That’s part of the illusion. If it wasn’t secret, people wouldn’t find it so fascinating,” Pattenden said. “It is like one of those locked-box routines. They’ve got the smoke just like a magician has, and then the pope appears on the balcony. It’s a classic misdirection.”

In “Conclave,” Fiennes’s character, Cardinal Thomas Lawrence, addresses the need to have faith. “If there was only certainty and no doubt, there would be no mystery,” he says. “And, therefore, no need for faith.” Mystery begets faith. Not knowing is the point.