A digital signature is an electronic signature used to authenticate the identity of the sender of a message or the signer of a document, and possibly to ensure that the original content of the message or document that has been sent is unchanged. It can be used with any kind of message, whether it is encrypted or not, simply so that the receiver can be sure of the sender's identity and that the message arrived intact. Digital Signature Certificates can be used for eFiling of Income Tax Returns, eTendering in India on Government Websites such as Indian Railway Catering and Tourism Corporation, and also Director General of Foreign Trade, Ministry of Corporate Affairs and Registrar of Companies Applications
A Digital Signature Certificate, like hand written signature, establishes the identity of the sender filing the documents through internet which sender can not revoke or deny. A Digital Signature Certificate is not only a digital equivalent of a hand written signature it adds extra data electronically to any message or a document where it is used to make it more authentic and more secured. Digital Signature ensures that no tampering of data is done once the document has been digitally signed. A DSC is normally valid for 1 or 2 years, after which renewal is required.