(Pawel Kopczynski/Reuters)

The FBI’s investigation of the two San Bernardino, Calif., shooters has revealed much about the attackers’ backgrounds. We know now that they met online through a dating site, were radicalized a couple of years ago and eventually pledged support to the Islamic State on social media.

But there is one detail that many in Congress and in the tech community are anxiously waiting to hear: whether the shooters ever used encrypted messages to communicate their plans for the shooting.

Without a doubt, a revelation that such technology was used would reignite the debate on Internet encryption — the coding of online information so that only those sending and receiving a message can see it — and whether governments should regulate how tech companies ensure privacy online.

The issue has become particularly salient due to the recent terrorist attacks across the globe, especially as groups like the Islamic State take advantage of online platforms to disseminate information and plan attacks. President Obama briefly touched on the topic in his address to the nation on the shooting, urging “high-tech and law enforcement leaders to make it harder for terrorists to use technology to escape from justice.”

The debate has become more and more lopsided as digital technology has rapidly developed. Originally, encryption technology was classified as a “munition” in the United States, meaning it was treated as a military weapon and subject to regulation. By the mid-’90s, however, the government effectively gave up on keeping it under control, as concerns mounted that the government was intruding on privacy and that “backdoors” into computers and phones would end up harming security. Now, practically everything is encrypted — your phone messages, your emails, your bank account, as well as popular messaging apps such as Facebook and Telegram used by everyone from teenagers to potential terrorists.

In many ways, that’s a very good thing. Encryption is designed to protect people from hackers and criminals who want to steal personal information. In general, it’s seen as an effective tool to prevent crime and protect privacy, which is why the tech industry stands nearly unanimously in favor of the technology.

The value of the technology is called into debate when it is used to protect those who want to do harm — like terrorists. Restrictions on encryption are mostly supported by those in national security and defense, who call for regulation of the technology so the government can more easily access hidden information. The FBI has long argued that the world of crime is “going dark” thanks to encryption, and though it hasn’t yet been proved that the terrorists in Paris used encrypted communication, CIA director John Brennan called the attacks a “wake-up call” in terms of Internet security.

The battle over encryption is a reemergence of the age-old debate pitting privacy against security. However, it’s clear the issue will only become more divisive over time, as we continue to hurtle into a digital era of more advanced technology — one in which terrorist groups and criminals can increasingly find refuge and connection on social media and the dark places of the Internet.

When the technological landscape is continuously redesigning itself, how ought we to monitor the world? Should we? And as we continue to venture further into this debate, is there any way for the technology and intelligence communities to cooperate with one another?

Over the next few days, we’ll hear from:

Nicholas Weaver, computer security researcher at University of California Berkeley’s International Computer Science Institute,

Cyrus Vance Jr., Manhattan district attorney,

Matthew Blaze, associate professor at the University of Pennsylvania,

Mark Wallace, CEO of the Counter Extremism Project and former U.S. Ambassador to the United Nations,

Rita Katz, founder of Site Intelligence Group,

James Dempsey, executive director of the Berkeley Center for Law & Technology.