The National Security Agency (NSA) has secretly circumvented or cracked much of the encryption that protects commerce, banking, trade secrets, medical records, e-mails, Web searches, Internet chats and phone calls, according to newly disclosed documents. In some cases the NSA collaborated with technology companies to insert “back doors� into encryption software, while in other cases it hacked into company servers to get encryption keys, according to documents provided by former NSA contractor Edward J. Snowden.

The NSA's mission is to intercept and decode communications from terrorists and rival nations to uncover plots and threats aginst the United States. Code breaking helped the United States and its allies win World War II as well as aided in tracking down modern terrorists. But, some experts worry NSA's campaign to bypass and weaken encryption could undermine the security of U.S. communications and expose American Internet users to attacks by hackers.

The documents stated that the program needed absolute secrecy to be effective. Intelligence officials asked the Guardian, New York Times and ProPublica not to publish reports on the program saying that it might prompt foreign targets to switch to new forms of encryption or communications that would be harder to collect or read. The newspapers removed some specific facts but decided to publish because of the value of a public debate about the program.

NSA says: The program is designed to "insert vulnerabilities into commercial encryption systems ... To the consumer and other adversaries, however, the systems' security remains intact." -- Agency documents.

British spy agency says: "For the past decade, NSA has led an aggressive, multi-pronged effort to break widely used Internet encryption technologies." -- Government Communications Headquarters.

Cryptography expert says: "The risk is that when you build a back door into systems, you're not the only one to exploit it. Those back doors could work against U.S. communications, too." -- Matthew Green, Johns Hopkins University.