When the U.S. Navy created Tor, a software that enables people to use the Internet anonymously, it didn't envision someone like Edward Snowden.
Quite the opposite: military programmers originally built the software in the mid-1990s to support government spying operations.
Yet last month, a photograph of Snowden, who leaked a trove of secrets about U.S. government surveillance, showed a sticker on his laptop supporting the Tor Project, the nonprofit that runs the anonymity network.
The image underscored the diverse -- and sometimes conflicting -- community of people using and supporting Tor to communicate anonymously on the Web.
Tor, which can be downloaded online, operates like a browser -- albeit slower because it is bouncing packets of data across several continents to protect anonymity. Journalists, whistleblowers, domestic abuse victims and dissidents living under repressive regimes use Tor to bypass government censors and prevent their online movements from being tracked. The U.S. State Department provides funding to the Tor Project to promote Internet freedom in other countries.
But the anonymizing software has also been used by whistleblowers to leak sensitive U.S. government secrets. Though it's unclear whether Snowden used Tor to disclose details about NSA surveillance to reporters, Wikileaks has reportedly used the software to protect whistleblowers.
"Tor's importance to Wikileaks cannot be understated," Wikileaks founder Julian Assange told Rolling Stone in 2010.
While some use Tor to traffic government secrets, criminals also use Tor to peddle drugs, guns, murder-for-hire services, hacking tools and child pornography outside the reach of law enforcement, according to security experts.
And yet, for the Tor network to be truly anonymous, it must protect all who are using it -- even those whose actions are condemned by the U.S. government, Christopher Soghoian, the principal technologist at the American Civil Liberties Union, told The Huffington Post.
— John Perry Barlow (@JPBarlow) June 9, 2013
Snowden with a laptop with a Tor Project sticker on it.
"When you create a technology that allows activists to communicate anonymously, you don’t get to pick which activists use it," Soghoian said.
"If you want a network that's safe for dissidents and journalists, you have to allow the pedophiles, too," he added. "You have to take the good with the bad."
Tor masks people's online activity by routing traffic through layers of servers, or "nodes," around the world. Its creators likened the encryption method to layers of an onion, giving the software its original name: "The Onion Router." About 500,000 people use Tor every day, according to the Tor Network, which consists of a global network of more than 3,000 volunteers who host servers and promote freedom of speech and online privacy.
Kelley Misata, a Tor Project spokeswoman, said recent disclosures about NSA surveillance have raised the public's consciousness about anonymity tools.
"With the recent news out there, people are becoming a bit more aware of prying eyes in their traffic," she said.
But the NSA revelations have also prompted Tor's supporters to disclose the network's limits in fighting government surveillance.
"By itself, Tor does not protect the actual communications content once it leaves the Tor network," the Tor Project said in a blog post last month. The group said the software is "a key building block to build systems where it is no longer possible to go to a single party and obtain the full metadata, communications frequency, or contents."
Soghoian said activity on Tor is unlikely to evade NSA surveillance. Yet its multiple layers of encryption remain useful for people evading government surveillance and censorship in Iran, Syria or China, as well as criminals looking to escape the watchful eye of law enforcement, he said.
"Just because the NSA can watch what's on the Tor network doesn't mean the sheriff in a small town can," he said.
Or the FBI. In 2011, the FBI said an investigation into an illegal child pornography site was stymied because the site operators used the software to mask their location.
"Because everyone (all Internet traffic) connected to the Tor network is anonymous, there is not currently a way to trace the origin of the website. As such, no other investigative leads exist," the FBI said at the time.
Joseph V. DeMarco, the former head of the cyber crime unit at the U.S. attorney's office in New York, said a criminal who uses Tor "means that avenue of investigation is blocked off."
DeMarco said the FBI has other investigative methods for tracking down cyber criminals, including search warrants and informants. But Tor makes it "extremely difficult, if not virtually impossible" for law enforcement to identify some illegal activity on the Internet.
"Does that mean some people will get away with crimes? Sure," he said.
Some security experts have suggested that Tor's backers should be held responsible for supporting technology that thwarts criminal investigations.
"Ultimately, as with states, anonymization services should be held accountable for their users’ behavior if they do not cooperate with law enforcement," Robert Knake, who is now director of cybersecurity for the White House, told a congressional committee in 2010.
But law enforcement also uses Tor to infiltrate illegal websites and catch criminals who use the software to hide from them, according to Soghoian.
In addition, Tor's creators -- those in the government -- say the more people using the network, the better. Tor's wide range of users, including those engaging in illegal activity, only further assist the software's original purpose: to cloak U.S. spying efforts, according to Michael Reed, one of Tor's original developers.
"Of course, we knew those would be other unavoidable uses for the technology," Reed wrote in an online forum in 2011, describing Tor's use by criminals, dissidents and those seeking porn. "But that was immaterial to the problem at hand we were trying to solve (and if those uses were going to give us more cover traffic to better hide what we wanted to use the network for, all the better...)"
For now, the Tor Project says it is focused on improving the software's image by attending conferences to educate law enforcement and dispel the notion that Tor is primarily a haven for criminal activity.
"We live in a world where if you use anonymizing tools, people assume it's for nefarious reasons," Misata, the Tor Project spokeswoman, said. "We're trying to put the word out that they can be used for very benign reasons. As more people use it, it will feel less scary."
And as more people use it, it becomes easier for Tor users to blend into the crowd and remain anonymous.
"Anonymity loves company," she said.