The future will be encrypted, from the start of a conversation or data transmission to the end of it, if privacy activists and security specialists get their way.

But first they have to persuade Google, Facebook and others to abandon their business models and embrace an encryption model commonly referred to as end-to-end encryption.

On Monday, in a rare live video interview with Edward J. Snowden at the South by Southwest music festival in Austin, Tex., the former National Security Agency contractor took great pains to endorse end-to-end encryption, as opposed to the encryption methods supported by Google, Facebook, Skype and others, which decrypt a sender’s encrypted communication at their data centers before re-encrypting it en route to the recipient.

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Mr. Snowden called the companies’ encryption methods “deeply problematic,” noting that government agencies need only go to a communication provider with a court order, or break into their data centers, to gather a user’s information, rather than go to the individual.

This year, The New York Times reported that as part of the N.S.A.’s efforts to circumvent encryption, it was forcing companies to hand over their private encryption keys through court orders or surreptitiously stealing their encryption keys or altering their software or hardware.

Using end-to-end encryption, Mr. Snowden noted, which encrypts a message as it travels it from the sender’s computer to the recipient’s, forces government agencies to go directly to the individual, rather than through a secret court to their communications provider.

“The result is a more constitutional, more carefully overseen enforcement model,” Mr. Snowden said. “If they want to gather each user’s communications, they have to go to them specifically.”

A new partnership, started by Silent Circle and Lavabit, two privacy-conscious communications providers, called the Dark Mail Alliance is putting technology companies like Microsoft, Google and Yahoo on the spot by pushing them to put in place the alliance’s new end-to-end encrypted email protocol, but the initiative is off to a slow start.

“The real friction point is that the Yahoos, the Microsofts, the Googles are all making money mining off free email,” Mike Janke, one of the founders of the Dark Mail Alliance, said in an interview in November. “They say they’re concerned about our privacy, but this is their opportunity to show they really care.”

Four months after the Dark Mail Alliance set up shop, none of the major technology companies have adopted the protocol. Critics say that is because it directly conflicts with their business models, which depend on their ability to use and profit from consumer data.

“Google wants to sit between you and everyone you interact with and provide some kind of added value,” Christopher Soghoian, the principal technologist of the American Civil Liberties Union, said on a panel with Mr. Snowden on Monday. “They want to be in that connection with you, and that makes it difficult to secure those connections.”

Mr. Snowden acknowledged on Monday that end-to-end encryption was not a panacea, given efforts by the N.S.A., its partners and others to hack directly into devices and computers to read communications before they have been scrambled. His talk on Monday came before fresh disclosures from the trove of classified documents he leaked to selected journalists last year.

On Wednesday, Glenn Greenwald, reporting for The Intercept, a new journalism project financed by the eBay founder Pierre Omidyar, released new classified documents leaked by Mr. Snowden that added further evidence to a New York Times article that detailed efforts by the N.S.A. to hack into computers and devices on a huge scale. The agency was doing this, in part, so it could gain access to communications before encryption.

But Mr. Snowden said the agency’s efforts to gain a foothold in every device would be difficult.

“They can’t pitch exploits in every computer in the world without getting caught,” he said. “That is the value of end-to-end encryption, and that is what we need to be thinking about.”