Signing another person's key means you are giving trust to that person.
Before signing a key, you have to carefully check the key's fingerprint
to be sure that the key really belongs to that person.
To sign a key in your keyring:
-
Select the key you want to sign from the
Trusted Keys or
Other Collected Keys tabs,
-
Choose Sign from the toolbar
or ,
-
Select how carefully the key has been checked,
-
Indicate if the signature should be local to your keyring,
and if your signature can be revoked,
-
Click on Sign.