The head of the US government's secretive National Security Agency took the unprecedented step on Friday of asking a convention of unruly hackers to join him in an effort to make the internet more secure.
In a speech to the 20th annual Def Con gathering in Las Vegas, four-star General Keith Alexander stressed common ground between US officials and hackers, telling them privacy must be preserved and that they could help by developing new tools.
"You're going to have to come in and help us," Alexander told thousands of attendees.
Alexander rarely gives speeches of any kind, let alone to a crowd of hackers, professional defenders, and researchers whose discoveries of software and hardware vulnerabilities are used by both sides.
Conference founder Jeff Moss, known in hacking circles as The Dark Tangent, told the conference that he had invited Alexander partly because he wanted them to learn about one of the world's "spookiest, least known" organisations.
Attendees were respectful and gave modest applause, though several said they were concerned about secret government snooping and the failure of authorities thus far to stop foreign-backed attacks.
"Americans pay taxes so that federal agencies can defend them," said a researcher who asked not to be named. "I see it as a hard sell asking a business entity to spend money for the common good."
Alexander won points by wearing the hacker "uniform" of jeans and a tee shirt, wandering the halls and praising specific hacking efforts, including intrusion detection tools and advances in cryptology.
He also confronted civil liberties concerns that are a major issue for many researchers devoted to the internet.
The NSA sponsored a booth at the convention for the first time, which organisers placed next to one from the Electronic Freedom Foundation (EFF). The EFF has sued the government, claiming that it illegally tapped conversations of Americans.
Alexander spoke with staff at the EFF booth, telling them he believes the US government can secure the nation and also protect civil liberties. They did not discuss the pending litigation.
Panels at the conference include a discussion of government tracking of individuals through cell phone data.
Taking questions screened by Moss, Alexander adamantly denied that the NSA has dossiers on millions of Americans, as some former employees have suggested.
"The people who would say we are doing that should know better," he said. "That is absolute nonsense."
Alexander used the speech to lobby for a cyber security bill moving through the Senate that would make it easier for companies under attack to share information with the government and each other as well as give critical infrastructure owners some reward for adhering to future security standards.
"Both parties see this as a significant problem," he said, adding that the experts like those at Def Con should help in the process. "What are the standards that we should jointly set that critical networks should have?"
In addition to conducting electronic intelligence gathering, primarily overseas, the Defense Department-controlled NSA is charged with protecting the US military from cyber attacks.
Increasingly, it has been sharing its findings with the Federal Bureau of Investigation to aid in criminal cases and with the Department of Homeland Security, which warns specific industries of new threats.
Displaying a slide with the logos of several dozen of companies breached by criminals or spies in the past two years, Alexander said that only the most competent even knew they had been hacked.
"There are 10 times, almost 100 times more companies that don't know they've been hacked," he said.
As he walked the convention floor, he repeatedly asked hackers, including children attending a "Def Con Kids" conference, to consider joining the NSA once they have honed their skills.
"Keep working on this. We need you in the future," he said.
Many of the more than 10,000 hackers who crowded into the Rio casino conference centre did not seem particularly interested in the presence of the head of the biggest US spy agency, who was flanked by an entourage of plain-clothes guards and Def Con's own red-shirted security force who call themselves "goons."
"Nice to meet you," he said to several dozen hackers in line to buy lock picking equipment at one crowded booth. "How can I help you?"
The crowd did not respond, and the booth's organisers politely chatted with Alexander.
When he approached a hacker preparing for a "capture the flag" computer-takeover contest, the hacker waved casually, then returned to his laptop. A teammate later explained: "We were just too busy to chat."