Gmail’s New End-to-End Encryption Swaps X.509 Certificates For KACL

I Can’t Believe It’s Not E2EE

There is a bit of controversy over the new end-to-end encryption feature that Gmail is offering to business customers.  The traditional definition that security experts use requires that only the “sender and the recipient have the means necessary to encrypt and decrypt” a message.  This is handled by unique X.509 certificates which are unique to each user and are required to read encrypted mail, which means even your email admins are unable to read the contents of your communications.  This can be somewhat of a PITA to administrate and is not exactly cheap to implement and keep functional.

The new Gmail feature encrypts and decrypts emails in the browser, using a key access control list.  This list can be hosted locally or on a cloud service, the one place it cannot be kept is on a Google server.  This ensures that Google is unable to read the contents of any encrypted emails. What it doesn’t do is ensure your email admins cannot decrypt emails; they own the KACL and therefore the keys to any and all email being sent via the company’s Gmail service.  It also means that an attacker has a new target, if they can grab a copy of the list of keys they can read any mail that they intercept.

Google is offering a mix of convenience and security with this new service.   While it is certainly less complex and cheaper to implement than traditional E2EE using X.509 certs, it is not quite as secure.  It a perfect example of the challenges all security teams face daily.