In case of Hard copy signing, the message binds the owner of the message, but not so in case of digital world. E mails can the spoofed or manual signature on scanned copies can be duplicated, so a digital signature is used to achieve the properties of a manual signature. It establishes Authenticity (Establishing the identity of the Person who has signed it), Integrity (That the documents is unchanged after Signing it), Non repudiation (That the person who has signed cannot deny it later).