ProtonMail adds full PGP support and address verification

Improves compatibility with other services

ProtonMail, the Switzerland-based encrypted email and VPN provider, has introduced full support for PGP.

ProtonMail's cryptography is already based on PGP but its email was previously incompatible with other clients and plugins that use the same protocol - such as Startmail or Enigmail - meaning that users of these services couldn't easily communicate with ProtonMail subscribers in private. With ProtonMail now offering full support this is now be possible, although senders will still need to manually import the public keys of their recipients.

ProtonMail CEO Andy Yen said: "First, any ProtonMail user can now send PGP encrypted emails to non-ProtonMail users by importing the PGP public keys of those contacts. Second, it is also possible to receive PGP email at your ProtonMail account from any other PGP user in the world. You can now export your public key and share it with them."

Another development is address verification with trusted keys, which the firm says increases the security of communications between two ProtonMail users by allowing users to verify cryptographically the addresses of individual correspondents.

If ProtonMail's servers are compromised, man-in-the-middle attacks, where an attacker uses a fake public and private keys to read private emails, is possible. Address verification enables an additional layer of protection by allowing users to formally trust certain keys. This feature is aimed at activists, journalists anod others who require the utmost confidence that their communications are secure, the firm says.

There is also a new public key server at hkps://api.protonmail.ch which should make finding public keys easier for PGP users.

"Unlike other encrypted communications systems, such as Signal or Telegram, PGP doesn't belong to anybody, there is no single central server, and you aren't forced to use one service over another," said Yen.

"We believe encrypted communications should be open and not a walled garden. ProtonMail is now interoperable with practically any other past, present, or future email system that supports the OpenPGP standard, and our implementation of this standard is also itself open source."