"Of course, we have no way of knowing whether the NSA knows the secret numbers that break Dual_EC-DRBG. We have no way of knowing whether an NSA employee working on his own came up with the constants -- and has the secret numbers. We don't know if someone from NIST, or someone in the ANSI working group, has them. Maybe nobody does."

Mr. Klein was responsible for maintaining Internet switching equipment near the secret room, and said he was stunned to discover that special “splitter” equipment had been installed in his area to route copies of all Internet traffic diverted through his lines into the secret room. “What I saw is that everything’s flowing across the Internet to this government-controlled room,” he said. Later, Mr. Klein obtained three AT&T documents that he said revealed the computer and equipment design for the room — documents that the company maintains he kept improperly after leaving AT&T in 2004. Those designs, according to Mr. Klein and other telecommunications specialists who have reviewed them, would give the security agency. the ability to sift and reroute international and domestic communications and data from the AT&T lines to another site. “The physical apparatus gives them everything,” Mr. Klein said, adding, “A lot of this was domestic.”