Post-quantum protection is now available as an optional feature in Proton Mail across all plans, including the free tier.

How post-quantum protection works

Once enabled, Proton Mail generates new encryption keys designed to protect future encrypted emails against attacks from quantum computers. Because the feature relies on new encryption keys, users need updated Proton apps that support post-quantum protection. Older app versions do not support the new keys.

“Enabling PQC helps protect new encrypted emails going forward. It does not retroactively re-encrypt the emails already in your mailbox, for now,” Anant Vijay Singh, Product Lead for Proton Mail and Drive, explained.

Proton says end-to-end encrypted forwarding is not currently compatible with post-quantum protection. Enabling the feature pauses encrypted forwarding.

The company also says users may notice a small performance impact after enabling the feature, although Proton Mail should generally feel the same on current hardware.

To enable post-quantum protection, users need to sign in to their Proton account settings, open the “Encryption and keys” section, and select the option to enable post-quantum protection. Proton then asks users to confirm the change and enter their password before generating the new encryption keys.

After enabling the feature, users can continue managing their encryption and PGP keys as before, including generating additional keys, downloading PGP keys, and using them with other PGP-compatible services.

Proton is also adding support for OpenPGP v6, a newer framework that enables support for updated encryption algorithms, including post-quantum cryptography.

The company says it is working to standardize quantum-safe encrypted email across the open email ecosystem, including with projects such as Thunderbird, so these protections can work between providers and support users regardless of which email service they use.