These keys can then be used by other Wt applications, or applications based on other libraries, to encrypt and sign data. As such, it suits my personal needs.
In particular, K7 needs the environment variable WT_APP_ROOT that should point to the directory containing configuration and translation files. In the project's tree, it's WTAPPROOT/K7.
This file is hard coded as k7config.json, and must be found in WT_APP_ROOT.
It controls access to the application. All users must authenticate by sending a client X509 certificate, and access is allowed if the subject's common name is listed as a JSON key in the configuration file.
An allowed user can always view keys. He can optionally import any GPG key, and delete GPG public keys. Key editing is also controlled in the configuration file.
An allowed user can optionally delete private GPG keys that he controls.