Whistleblower Edward Snowden has called for full end-to-end encryption of Internet services in an effort to thwart the mass surveillance of users.
He made the plea during a panel discussion at the South by Southwest (SXSW) conference conducted via a live video chat.
Snowden also accused the current NSA boss Keith Alexander and his predecessor Michael Hayden of making the US more vulnerable to cyber attacks rather than protecting it.
He said that the US Constitution had been "violated on a massive scale" by the spy agencies.
"America has more to lose than anyone else," Snowden said, referring to the NSA asking tech companies to weaken their products and services so as to make it possible to exploit them for surveillance purposes.
Encrypting every bit of the communication chain automatically is the secret to keeping the web safe from the prying eyes of spies and cyber crooks. The measure would not damage national security, but rather improve it, Snowden believes.
This would mean fully encrypting hard disks as well as networks, using anti-tracking software and hiding your Internet Protocol address with tools such as The Onion Router (TOR) as well as Pretty Good Privacy (PGP) for email, Snowden said.
"The US government still has no idea what documents I have given to journalists - because encryption works," he said.
However, such tools are not easy for ordinary people to use, and may not help in every case.
"If the NSA really wants to get you, they will get you anyway," Snowden conceded.
During the discussion, the former NSA contractor laid into web giants such as Google, Yahoo and Facebook for only encrypting services after they had been found vulnerable to interception.
Fellow panellist and American Civil Liberties Union (ACLU) technologist Chris Soghoian expounded on this, saying many tools such as Google's Chrome web browser and Android mobile operating system are made by advertising companies.
As such, the companies are reluctant to introduce full encryption of user data becase it makes it harder for them to machine read it and display contextual advertising, he opined.
Snowden said that another consequence of the revelations was that cryptography geeks working for the large web companies were "pissed off" and had become "radicalised" by the privacy violations of the spy agencies.
This was partly confirmed in an earlier talk at SXSW by Google chairman Eric Schmidt, who claimed that data held by the company is now safe from the NSA in the United States.
Snowden spoke to the SXSW delegates from an unknown location, possibly in Russia, via the Internet using Google Hangout.