What Is Digital Signature?

This section describes the digital signature of a digital document. A digital signature is the message digest of the document encrypted by sender's private key. Receiver can decrypt the digital signature with sender's public key and compare it with the message digest of the received document.

In earlier part of the book, we discussed one important application area of the PKI (Public Key Infrastructure) technology. That is the HTTPS (Hypertext Transfer Protocol Secure) to provide encrypted communication and secure identification of Web servers.

Now we can look at another application area of the PKI technology, digital signature.

What Is Digital Signature? I like the definition from wikipedia.org: "A digital signature or digital signature scheme is a mathematical scheme for demonstrating the authenticity of a digital message or document. A valid digital signature gives a recipient reason to believe that the message was created by a known sender, and that it was not altered in transit."

The digital signature scheme is shown in this picture from globus.org:
Digital Signature Scheme

The diagram shows you that:

Note that the picture above only verifies the integrity of the received document. It does not cover the verification of sender's identity. See next section for details on this.

Last update: 2011.

Table of Contents

 About This Book

 Introduction of PKI (Public Key Infrastructure)

 Introduction of HTTPS (Hypertext Transfer Protocol Secure)

 Using HTTPS with IE (Internet Explorer) 10

 Using HTTPS with Chrome 40

 Using HTTPS with Firefox 35

 Perl Scripts Communicating with HTTPS Servers

 PHP Scripts Communicating with HTTPS Servers

 Java Programs Communicating with HTTPS Servers

 Certificate Stores and Certificate Console

 .NET Programs Communicating with HTTPS Servers

 CAcert.org - Root CA Offering Free Certificates

 PKI CA Administration - Issuing Certificates

Digital Signature - Microsoft Word 2007

What Is Digital Signature?

 PKI Digital Signature

 Applying Digital Signatures with MS Word 2007

 Creating a Digital ID and Sign Word Documents

 View Digital Signatures in Word Documents

 Viewing Digital ID Created by MS Word

 Obtaining a Trial Digital ID from ARX CoSign

 Viewing Digital ID Obtained from ARX CoSign

 Digital Signature - OpenOffice.org 3

 S/MIME and Email Security

 PKI (Public Key Infrastructure) Terminology

 Outdated Tutorials

 References

 PDF Printing Version