gnome-keysign 1.0.1-3ubuntu1 (amd64 binary) in ubuntu eoan

 GNOME Keysign is a tool for signing OpenPGP keys.
 .
 Its purpose is to ease signing other peoples' keys. It is similar to caff,
 PIUS, or monkeysign. In fact, it is influenced a lot by these tools and
 either reimplements ideas or reuses code. Consider either of the above
 mentioned tools when you need a much more mature codebase.
 .
 In contrast to caff or monkeysign, this tool enables you to sign a key
 without contacting a key server. It downloads an authenticated copy of the
 key from the other party. For now, the key is authenticated by its fingerprint
 which is securely transferred via a QR code. Alternatively, the user may type
 the fingerprint manually, assuming that it has been transferred securely via
 the audible channel.
 .
 After having obtained an authentic copy of the key, its UIDs are signed. The
 signatures are then encrypted and sent via email. In contrast to monkeysign,
 xdg-email is used to pop up a pre-filled email composer windows of the mail
 client the user has configured to use. This greatly reduces complexity as no
 SMTP configuration needs to be obtained and gives the user a well known
 interface.