Interface of a
Signer that requires user interaction during the signing process. Any
Signer that implements this interface, can be used within the
SignatureSignerDialog to request a password from the user.
Set a listener for being notified of important events that require user interaction.
Can be used to provide a password to the signer, which might be used to unlock a private key
||A password that should be used by the signer, or
null if no password