The National Security Agency is bypassing encrypted Internet connections because the encryption data is all the same, researchers posited this week. It has long been believed the NSA had a way to bypass common types of encryption, but its methods haven’t been known.

“There have been rumors for years that the NSA can decrypt a significant fraction of encrypted Internet traffic,” Alex Halderman and Nadia Heninger wrote in a study Wednesday. “The key is, somewhat ironically, Diffie-Hellman key exchange, an algorithm that we and many others have advocated as a defense against mass surveillance.”