The Web is an interconnected global information system that provides resources suitable for consumption directly by humans. In this model, security is critical for many of these resources (login-password authentication at restricted sites, SSL encryption of credit cards and other personally identifiable confidential information). It only makes sense, then, that application-to-application Web services need at least this much security as well.

In fact, because Web services expose critical and valuable XML-encoded business information, Web services security is a critically important concept to fully understand. For one thing, trade secret pilfering is already a large problem, and without security, Web services might even make this situation worse. The reason is that Web services can be thought of as allowing in strange, new users who might take your company's valuable business secrets out.

This section covers basic security concepts to establish the vocabulary that will be used throughout this book. Keeping communications secret is the heart of security. The science of keeping messages secret is called cryptography. Cryptography is also used to guarantee trust in a known identity across a network by "binding" that identity to a message that you can see, interpret, and trust. An identity asserting itself must be authenticated by a trust authority to a previously established identity known to the authority for the binding to be valid. After you know the identity, authorization allows you to specify what the individual with that identity is allowed to do. When you receive a secret message, you need to know that nothing in the message has been changed in any way since it was published, an attribute called integrity. When cryptography successfully keeps a message secret, it has satisfied the requirement for confidentiality. At times, you might want to know that someone who received confidential information cannot deny that she received it, an important security concept called non-repudiation.

Most of these core security concepts depend on encryption technologies, so before you look at any of them more closely, take a look at the fundamentals of encryption.

This chapter is from Securing Web Services Security with WS-Security, by Jothy Rosenberg and David Remy (Sams, 2004, ISBN: 0672326515). Check it out at your favorite bookstore today. Buy this book now.