WhatsApp end-to-end encryption: How it works and what it means for users.
WhatsApp is now end-to-end encrypted at all times. This will ensure that users’ messages, videos, photos sent over WhatsApp can’t be read by anyone else — not WhatsApp, not cyber-criminals, not law-enforcement agencies. Even calls and group chats will be encrypted.
WhatsApp co-founder Jan Koum announced the update on his Facebook page, stating that the company has been working on the feature for the last two years.
So what is end-to-end encryption and how exactly does it work in WhatsApp?
WhatsApp is using “The Signal Protocol”, designed by Open Whisper Systems, for its encryption.
In its White Paper, explaining the technical details of the end-to-end encryption, WhatsApp says that “once the session is established, clients do not need to rebuild a new session with each other until the existing session state is lost through an external event such as an app reinstall or device change.”
It reads, “clients exchange messages that are protected with a Message Key using AES256 in CBC mode for encryption and HMAC-SHA256 for authentication. The Message Key changes for each message transmitted, and is ephemeral, such that the Message Key used to encrypt a message cannot be reconstructed from the session.” It also says that calls, large file attachments are end-to-end encrypted as well.
Note that the ever-changing message key can mean a delay in some messages getting delivered, according to the paper.
It should be noted that feature is enabled by default in WhatsApp, which means that if you and your friends are on the latest version of the app, all chats will be end-to-end encrypted. Unlike say Telegram where users have to start a secret chat to enable the feature, WhatsApp has the feature on at all times. Users don’t have the option of switching off end-to-end encryption.
Users need to be on the same versions of WhatsApp to ensure that their chats get end-to-end encrypted. If you’ve recently updated the app, and you start a chat with someone else (also on the new version) you are likely to see a message saying, “Messages you send to this chat and calls are now secured with end-to-end encryption.