There are several problems if multiple keys are selected in the key
manager.

1. Keys of the wrong protocol should not silently be skipped. However, for deletion we could switch the protocol as needed.

2. Sending and receiving keys should not be allowed if only x.509 keys are selected.

3. The sign/delete dialog pops up for each key. Choosing "no" stops signing/deleting for all remaining keys. A better method would be to skip only that key and add a cancel button to entirely stop signing/deleting.