Both Yahoo and Google are promising to encrypt their mail services -- Gmail, and Yahoo Mail -- sometime next year. Yahoo's new chief information security officer Alex Stamos told attendees of the Black Hat hacker and security conference here on Thursday that at some point in 2015, Yahoo Mail would not only be encrypted end-to-end, but would be compatible with the end-to-end encryption that Google is working on for Gmail.

Yahoo encrypted webmail at the data center level earlier this year, but encrypting emails sent between accounts has proven elusive so far.

Yahoo will be leveraging the security community to improve the encryption. Stamos said that Yahoo will release the encryption source code sometime this fall, "so that the open source community can help us refine the experience and hunt for bugs."