A sender of an e-mail message applies a digital signature to the digest of the message.
This action provides assurance of the:
date and time stamp of the message.
identity of the originating computer.
confidentiality of the message’s content.
authenticity of the sender.
The signature on the digest can be used to authenticate the sender. It does not provide assurance
of the date and time stamp or the identity of the originating computer. Digitally signing an e-mail
message does not prevent access to its content and,therefore, does not assure confidentiality.