The open-source browserextension "Mailvelope" enables the exchange of encrypted e-mails with the help of webmailers using the OpenPGP encryption standard. ABSI project has extended Mailvelope so that

• webform content can be transmitted end-to-end in encrypted form, independent of the website operator, right through to the recipient of the form data,
• the cryptography library that is used,OpenPGP.js, is extended to be compatible with the OpenPGP standard,
• a local GnuPG installation can be integrated so that users can use native applications if they wish (e.g. for key management), and
• a key exchange procedure is established that is as transparent as possible for the user: distribution of the public key by Web Key Directory (WKD) via HTTPS query

The project, initiated by the BSI, began in January 2018 and was undertaken by two independent service providers. The further development of Mailvelope was carried out by a consortium of Intevation GmbH and Mailvelope GmbH and the audit by SEC-Consult.

The objective of the project was aimed at making the installation, configuration and use of end-to-end encryption much more user-friendly, as well as increasing the use of encryption in e-mail and form exchange through extensive automation. In future, it will also be possible to use the software to make confidential enquiries, for example, to doctors or banks via web forms.

The exchange of public keys required for encryption is automated and does not require any user interaction. To do this, providers of contact forms must have the form adapted by the creator of the website according to the documentation (GitHub Mailvelope). Users only have to install and configure the Mailvelope application once.

In addition, an audit of the product's security features was commissioned to strengthen trust in the developments. Alongside the implementation of cryptographic procedures, another key focus of the audit was the existence of routines for monitoring users or compromising private data. This not only ensured a high level of quality, but also meant that problems could be identified straight after development and solved before release.

As part of the coordinated vulnerability management with developers the following issues were successfully resolved in Mailvelope:

• Clickjacking (CVE-2019-9147)
• Private Key Operations Require no User Interaction (CVE-2019-9149)
• Key Import User Interaction Bypass (CVE-2019-9150)
• Missing Message and Key Validity Checks (CVE-2019-9148)

and in OpenPGP.js

• Invalid Curve Attack (CVE-2019-9155)
• Message Signature Bypass (CVE-2019-9153)
• Information from Unhashed Subpackets is Trusted (CVE-2019-9154)

The full results of the audit are presented in the English-language report:

Mailvelope Extensions Security Audit