Digital signatures allow us to verify the author, date and time of signatures, authenticate the message contents. It also includes authentication function for additional capabilities.
A digital signature should not only be tied to the signing user, but also to the message.
There are several reasons to implement digital signatures to communications:
Digital signatures help to authenticate the sources of messages. For example, if a bank’s branch office sends a message to central office, requesting for change in balance of an account. If the central office could not authenticate that message is sent from an authorized source, acting of such request could be a grave mistake.
Once the message is signed, any change in the message would invalidate the signature.
By this property, any entity that has signed some information cannot at a later time deny having signed it.