The National Geospatial-Intelligence Agency (NGA) released a report in June detailing what it calls a “data tsunami.” By the end of this decade, there will be anywhere from 50 billion to 200 billion networked devices on a planet of some 8 billion people. “For the intelligence community, this equates to 40 zettabytes of data, or 1 sextillion bytes,” the NGA states. “Described in more familiar terms, this is the equivalent of every person on the planet having 174 newspapers delivered daily.” Viewed another way, that’s more data than 7 billion Libraries of Congress could hold.

In the surveillance state Obama has built, this deluge threatens to bury the few needles that might exist — warnings of attacks, signals of radicalizing groups, rallying cries of extremist recruiters — even deeper in the proverbial haystack. So, too, does encryption: Once a tool used mostly by spy agencies and militaries, encryption is becoming commonplace in everyday digital chatter to keep government eyes and ears out. Gmail offers it. WhatsApp began providing its billion-plus users with automatic encryption in April. In July, Facebook announced that it would soon give the option of end-to-end encryption on its Messenger app. More services will surely follow.

Speed is a critical component in breaking encryption because most codes are based on factoring extremely large prime numbers. Conducting what’s known as a “brute force” attack — trying every possible combination of digits — using even the most powerful computers in operation would take centuries or longer to succeed.

Obama, though, signed an executive order in July 2015 urging the creation of an exaflop supercomputer — a machine about 30 times faster than anything in existence. It would be capable of conducting more than a quintillion (1,000,000,000,000,000,000) operations per second. The president’s charge to build was mostly targeted at the scientific community; behind the scenes, however, the NSA has been preparing to breach the exaflop barrier since 2011.

That year, the agency secretly built a 260,000-square-foot facility at the Oak Ridge National Laboratory in Tennessee, the same place where the Manhattan Project developed the atomic bomb. Its research focuses on hitting the computing speed that would not only give the agency an edge over encryption, but also provide it with better cataloging capabilities to tackle the ocean of data already arriving daily at complexes like the one in Bluffdale, Utah.

The government is also finding ways to cheat, most notably through Bullrun, a code-named program run jointly by the NSA and the GCHQ. The agencies clandestinely collaborate with technology companies and internet service providers to “insert vulnerabilities into commercial encryption systems,” as reported by the Guardian. As of 2010, according to a top-secret GCHQ PowerPoint, the NSA had already achieved a breakthrough: “Vast amounts of encrypted Internet data which have up till now been discarded are now exploitable,” the leaked slides state. By 2015, the British agency hoped to have cracked the encryption of 15 major internet companies.

Looking further into the future, Obama’s NSA has also explored quantum computing — technology that, theoretically, could defeat encryption for good. Its science breaks all the rules. Today, data are stored in binary bits — either ones or zeros — but in quantum computing, so-called qubits could be both one and zero at the same time. This would allow for almost incomprehensible operating speeds. According to documents released by Snowden, the NSA has been working to build “a cryptologically useful quantum computer” as part of a research program broadly called Penetrating Hard Targets.

Ultrafast computing could be a game-changer in U.S. intelligence. It would break the last line of defense against government intrusion. Though this wouldn’t necessarily — or even likely — guarantee that security threats could be identified, it would allow the surveillance state to seize every bit of power that its backers, including Obama, have sought to give it.

After the White House panel set up to review NSA surveillance in 2013 suggested halting efforts to undermine commercial encryption, the president demurred. In a speech — one of the few he’s given on surveillance in his second term — Obama kept to the middle of the political road. “We have to make some important decisions about how to protect ourselves and sustain our leadership in the world, while upholding the civil liberties and privacy protections that our ideals and our Constitution require,” he said. “We need to do so not only because it is right, but because the challenges posed by threats like terrorism, and proliferation, and cyberattacks are not going away anytime soon.”

Zack Whittaker, the security editor for ZDNet, summed up Obama’s remarks in a headline: “Keep calm and carry on spying.”

Whoever wins the upcoming presidential election will probably do just that. In response to the Orlando shooting in June, Hillary Clinton said, “I have proposed an intelligence surge to bolster our capabilities across the board with appropriate safeguards here at home” — but offered no details on what that would entail. She has called for Snowden to return from Russia and face trial, and while supporting the end of the NSA’s metadata program, she’s suggested that the agency never broke the law. “I think it’s fair to say the government, the NSA, didn’t, so far as we know, cross legal lines, but they came right up and sat on them,” she told an audience at a San Francisco technology summit in August 2014.

Donald Trump’s rhetoric, meanwhile, suggests that he would prioritize making America’s surveillance empire as powerful as possible. “I think security has to preside, and it has to be preeminent,” he told Fox News in June 2015. Trump has also said NSA reconnaissance is just a fact of modern American life. “I assume that when I pick up my telephone, people are listening to my conversations,” he told radio host Hugh Hewitt last December, implying that Americans should just get used to being spied on.

Whistleblowers, it seems, would not fare well under a Trump administration. “If I were president, [Russian President Vladimir] Putin would give him over,” Trump said of Snowden in a July 2015 appearance on CNN. In 2013, speaking on Fox & Friends, he was even tougher. “I think Snowden is a terrible threat. I think he’s a terrible traitor, and you know what we used to do in the good old days when we were a strong country?” Trump asked. “You know what we used to do to traitors, right?” One of the hosts interjected, “Well, you killed them, Donald.” Trump agreed.

This is Obama’s legacy on surveillance: a shadow state of brick and mortar, hardware and software, satellites and eavesdroppers, that is ready to grow on the next president’s command. How big is too big, though, is a question the outgoing president has never answered fully. At what point does gathering data become an end in itself, rather than a means to an end? Is the U.S. government already there or approaching it?

Unless answers come, 50 years from now, the world may look back at Obama’s architecture of surveillance — full of radomes, windowless walls, phone taps, and double-ringed fences — with the same puzzled astonishment that 1950s bomb shelters elicit today.

Correction, Sept. 12, 2016: The Delta IV Heavy is the most powerful American rocket in use today. A previous version of this article misstated that it was the most powerful rocket in the country’s history.

A version of this article originally appeared in the September/October 2016 issue of FP magazine.