How does WhatsApp end-to-end encryption work?

Encryption is essential for the secure exchange of messages and content via app. But how does WhatsApp end-to-end encryption work?

WhatsApp has relied on end-to-end encryption (E2EE) for over a decade to ensure the privacy and security of its users. This encryption is intended to prevent third parties or WhatsApp itself from accessing sent messages.

With end-to-end encryption, messages remain encrypted throughout their transmission. The sender and receiver each have their own key. While the sender's device encrypts messages with a public key, the recipient's device decrypts the message with a private key. This is intended to guarantee that even if the message is intercepted, the content remains unreadable.

How does WhatsApp end-to-end encryption work?

WhatsApp uses the Signal protocol for encryption. This comes from the software developer group Open Whisper Systems (OWS. It is also used in the messenger Signal of the same name. The protocol ensures that the end device encrypts every message, every photo and every video before it reaches the WhatsApp server.

The system generates a private and a public key for communication. The private key remains with the sender, while your contacts can access the public key.

If someone sends a message to someone, the system encrypts it with the recipient's public key. This creates an illegible character string that can only be converted back into the original text or content using the private key.

In short: the public key can only encrypt, while the private key can only decrypt. The app also syncs messages between different devices of a user. Each device generates its own key, which means that the encryption exists independently on each device.

Keys guarantee secure sending of messages

When you send a message, your device first encrypts it with a special message key. This key changes with each new message, which is also known as “ratcheting”. For each new message, the system generates a new key, so old keys are invalid for new messages.

This is intended to provide additional protection, as even compromised keys do not allow access to future messages. WhatsApp also uses so-called Message Authentication Codes (MACs) to ensure that malicious actors cannot manipulate messages during transmission. This is intended to offer protection against unnoticed changes on the path between the sender and receiver.

How does synchronization between multiple devices work?

WhatsApp allows users to sync messages across multiple devices without compromising security. This is done by generating an additional key that the app stores on the primary device.

Users can scan a QR code when setting up a new device, which allows the algorithm to classify the new device as trustworthy. Reception is then possible on the newly set up device.

End-to-end encryption also works in group chats. The app creates a special group key that all members of the group receive. When a member leaves the group or a new member joins, the algorithm updates the key. This is to ensure that former members cannot decrypt new messages.

WhatsApp relies on relatively modern encryption technology to protect the privacy of its users. By using end-to-end encryption (E2EE), messages, calls and media content remain secure even when sent or received across multiple devices.

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