“WhatsApp is the first global messaging service of its size to offer end-to-end encrypted messages and backups,” said in a Facebook post on Friday.
In a separate blog post, the company said to protect message privacy, WhatsApp has provided end-to-end encryption by default so messages can only be seen by the sender and recipient and no one in between. “Now we are planning to give people the opportunity to protect their WhatsApp backups with end-to-end encryption,” write Slavik Krassovsky and Gabriel Cadden.
Users can already back up their WhatsApp message history via cloud-based services such as Google Drive and iCloud. WhatsApp has no access to these backups and they are secured by the individual cloud-based storage services.
But now, when people choose to enable end-to-end encrypted (E2EE) backups as soon as they are available, neither WhatsApp nor the backup service provider can access their backup or backup encryption key.
The company said in order to enable E2EE backups, it developed an entirely new encryption key storage system that works with both iOS and Android. When E2EE backups are activated, backups are encrypted with a unique, randomly generated encryption key.
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Users can secure the key manually or with a user password. When someone chooses a password, the key is stored in a Backup Key Vault, which is based on a component called a Hardware Security Module (HSM) – specialized, secure hardware that can be used to securely store encryption keys. If the account holder needs access to their backup, they can access it with their encryption key or use their personal password to retrieve their encryption key from the HSM-based Backup Key Vault and decrypt their backup.
The HSM-based Backup Key Vault is responsible for enforcing attempts to verify passwords and making the key permanently inaccessible after a minimal number of unsuccessful access attempts. “These security measures provide protection against brute force attempts to retrieve the key. WhatsApp only knows that there is a key in the HSM. It won’t know the key itself, ”WhatsApp said.
The news giant said its front-end service ChatD handles client connections and client-server authentication and will implement a protocol that sends the keys to the backups to and from the WhatsApp servers.
“The client and the HSM-based backup key vault exchange encrypted messages, the content of which ChatD itself cannot access. The HSM-based backup key vault is located behind ChatD and offers high-availability and secure storage for the encryption keys used for the backups” , explained WhatsApp, adding: “The backups themselves are generated as a continuous data stream that is encrypted with symmetric encryption with the generated key. If E2EE backups are enabled, a backup can then be stored outside the device after encryption (e.g. to iCloud or Google Drive). ”
According to WhatsApp, it serves over 2 billion people, and one of the core challenges of this product was making sure the HSM-based Backup Key Vault was working reliably. To ensure that the system is always available, the HSM-based Backup Key Vault service is geographically distributed across multiple data centers to keep it operational in the event of a data center failure.