Digital signature is quite a common term these days. In fact, with the advent of information technology, the importance of digital signature has been increasing remarkably. A digital signature is required to authenticate an electronic document, just like a handwritten signature is required to authenticate a printed or hand written document. In any document, that has legal importance, a signature is an essential part of it. As more and more documents are now used, or transferred digitally, the importance of digital signature is obvious. A digital signature actually offers more security than any kinds of handwritten signatures.