Как исправить эту проблему BADSIG?

W: GPG error: http://repo.vivaldi.com/stable/deb stable Release: The following signatures were invalid: BADSIG 793FEB8BB69735B2 Vivaldi Package Composer KEY06 <packager@vivaldi.com>
E: The repository 'http://repo.vivaldi.com/stable/deb stable Release' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.