SAN FRANCISCO: Yahoo is teaming up with rival Google to develop a secure email system as major tech companies respond to growing public concern about digital privacy and security.

The two are exploring ways to bring existing advanced encryption technology into the mainstream. Alex Stamos, Yahoo's chief information security officer, explained to the Wall Street Journal that in addition to the technical hurdles to be overcome there was a need to educate the public on the limits of the technology which does not encrypt metadata.

"We have to make it clear to people it is not secret you're emailing your priest," he said. "But the content of what you're emailing him is secret."

Nor is PGP [Pretty Good Privacy] encryption technology user-friendly which may limit the uptake of the service by users. As Christopher Soghoian, a security and privacy researcher at the American Civil Liberties Union, put it: "How do you get children to eat their spinach? PGP is even less tasty than spinach."

Some observers have suggested that is just what Google and Yahoo are betting on, since if everyone encrypted their emails they would not be machine readable and relevant ads could not be displayed alongside them.

Coincidentally, a recent report from the Online Trust Alliance, reported in Adweek, found that 91.7% of 800 consumer websites surveyed were failing to implement appropriate email security, making them vulnerable to hackers.

Just 6% of the top 500 internet retailers in the US, for example, met security standards, suggesting that this should perhaps be of more immediate concern to consumers than whether government agencies were reading their emails.

But there is no doubt that the issue has risen up the agenda. Five years ago the view of Eric Schmidt, Google CEO, was that "if you have something that you don't want anyone to know, maybe you shouldn't be doing it in the first place"; in 2014, however, that had changed dramatically: "In hawks versus doves, hawks win. Fight for your privacy".

A particular concern for consumers is how their data is used. A study of US and UK consumers for marketing consultancy Contagious I/O found that 81% of people in the UK have considered no longer using a product or service due to privacy concerns while a similar proportion want more regulation around how brands interact with their data.

Data sourced from Wall Street Journal, Adweek, The Observer; additional content by Warc staff