Google is working on the ultimate security and privacy feature.

It's called "End-to-End" encryption, and it's the best way to stop anyone from snooping on your emails. Google would turn your emails into jumbled code, and the only person who can see the email in plain text is the trusted person on the other end.

Hackers don't stand a chance. In fact, neither does the National Security Agency. It's the kind of encryption ex-NSA contractor Edward Snowden used to communicate with journalists before he went public last year with damning documents proving the extent of U.S. government surveillance. It's what spies use -- it's that good.

But End-to-End is not available just yet. In a blog post, Google said the program is in a public testing phase. After that, you'll be able to download the app and add it to your Google Chrome Web browser. If you use the browser, it'll work with any Web-based email provider.

"We recognize that this sort of encryption will probably only be used for very sensitive messages or by those who need added protection," wrote Stephan Somogyi, a Google product manager who oversees security and privacy, in the blog. "But we hope that the End-to-End extension will make it quicker and easier for people to get that extra layer of security should they need it."

Here's how Google's super encryption would work: Imagine you want to send a sensitive letter by mail. You can't just lick the envelope shut. Postal workers might open it. But they can't open a lock.