Home > Articles

The Foundations of Distributed Message-Level Security

📄 Contents

  1. The Challenges of Information Security for Web Services
  2. Shared Key Technologies
  3. Public Key Technologies
  4. Summary
This chapter is from the book

Security is one of the most vital topics in Web services development today and will be for the foreseeable future. The lack of maturity of standards and tools in this area is the reason most often cited for large organizations delaying their commitment to Web services. The most important security standards are ready now, though, and the tools are coming online. Importantly, these Web Services Security standards are really not groundbreaking; they are, in turn, just extensions of very well-established information security standards.

In Chapter 2, "The Foundations of Web Services," we introduced Web services as a new form of middleware for building and integrating distributed applications by sending XML messages between computing nodes. Making Web services secure means making those messages secure and keeping them secure wherever they go. This chapter builds on the preceding chapter by adding a solid foundation in the principles of distributed message-level security. Those principles depend on solid knowledge of shared key cryptography and public key cryptography. We begin by setting the information security context for Web services.

The Challenges of Information Security for Web Services

Securing distributed systems is hard. Securing exchanged information between those systems is harder. Securing Web services with their distributed, shared, and exposed information (XML messages) is much harder still. In the following sections, we address each of these challenges in order.

Security of Distributed Systems Is Hard

In distributed systems, you are not securing just one system, but many. In addition, you are securing the interconnections between the distributed systems. The goal of distributed systems is to make a collection of independent computers appear to their users as a single integrated system. When you can successfully integrate separate and distinct networked computers together, the integrated system can handle higher workloads, aggregate more functionality, and share data that previously was locked up and inaccessible. But the more access points there are, the more places an attacker has to attack. In other words, a distributed system has all the security issues of one system multiplied many times over.

These distributed system security issues include access control, identity management, authentication, password management, authorization, encryption of confidential information on each node, integrity of information passing between nodes, and more. This is the reason the CORBA security specification is 430 pages long.

Because Web services use the Web and enable and even encourage integration between systems across organizational boundaries using public networks, they are, in fact, much more distributed than CORBA or any previous form of middleware could contemplate. Web services, when used in remote procedure call mode, involve some of the same issues as CORBA object invocation security.

A service-oriented architecture—such as what can be achieved when Web services become pervasive—projects a vision of geographically distributed services, many of which are publicly available shared services incorporated into numerous applications. Knowing who is using these services, what these users are authorized to do, and how to protect all information at these nodes is a difficult security task.

Security of Exchanged Information (Messages) Is Harder

When security administrators think about securing their systems today, they typically think about securing their organization's "four walls." They think about perimeter security such as firewalls, intrusion detection, honeypots, and DMZs. None of these elements deal with the security of messages in transit. Security administrators focus most on access control security believing that, if they know for sure who has access to their network, they implicitly have secured their critical assets: their information. In fact, perimeter security schemes are really a proxy for information security, because all along, what people are really trying to protect is the information created, processed, or stored on the machines inside their perimeters.

Distributed applications send back and forth messages that are the command, control, and coordination that make the distributed applications function. This means you have the problems of computer and network security you always had, plus the problems of information security for critical command and control messages flowing through the distributed system. Transport-based security like SSL provides one type of protection for messages in transit—just server-to-server non-persistent confidentiality—but offers little or no control at the application level, which is the place where the messages have meaning.

Messages must remain intact from sender to receiver regardless of how many hops occur in between. Shared services create a many-hops scenario in which messages go through many service endpoints on the way to their destination. The receiver must know for sure who the sender was to establish trust, which is critical in all aspects of business. The sender must be able to control who is allowed to see her messages because vital (and confidential) information is contained in them. In the case of transmitted legal documents, being able to prove what transpired and repudiate any denials is critical. Messages need to remain persistently secure not just while in transit, but also when residing in permanent storage because the message might contain highly confidential information such as a credit card number, Social Security number, or business deal terms.

Security of Web Services Is Hardest

Web services add a new dimension to the challenges already faced with distributed systems. Critical security questions must be reliably answered. Who is the end user? How do you maintain security when routing messages through multiple servers? How do you maintain security when using shared services?

Web services are fundamentally about how to share the burden of—and derive the benefits from—computing across a distributed network of computers connected with Web infrastructure and standards. These messages—being XML—are text-based, readable, and self-describing. Security of Web services is about knowing whether the Web services are talking to the correct endpoints; the communications between all the disparate elements are kept confidential; the messages transported maintain their integrity at all times; and the entities for which these Web services are being invoked are known, trusted, and authorized to use the services and can be clearly identified to all other authorized services.

The good news is that Web Services Security builds on existing security standards; very little that is new is being proposed. In general, Web Services Security provides an XML-based abstraction layer for established security technologies that delivers confidentiality, integrity, non-repudiation, authentication, and authorization.

Why All the FUD about Web Services Security?

Some Web Services Security vendors, the analysts that cover these companies, and the media are spreading fear, uncertainty, and doubt (FUD) about how an organization must fully implement Web Services Security before deploying the first Web service. Because early Web service deployments tend to be simple, straightforward, internal, behind the firewall, point-to-point integrations, sophisticated Web Services Security technologies are not always necessary. In fact, the same security used by these companies for securing their Web sites—namely SSL—is usually sufficient.

For the vendors who are selling either a product or service that implements Web Services Security in some form, however, it is in their best interest to have the early Web services adopters firmly believe they cannot be successful without these vendors' products or services. This thinking is a huge stretch, to put it mildly.

When designing an information security strategy for a Web services deployment, you must think like an information security professional. Think in terms of confidentiality, integrity, and the other building block security principles. If your messages need legal non-repudiation, perhaps you need to employ more sophisticated technologies. But if all you need to do is keep messages confidential between point A and point B, maybe what you already know how to do so well (use SSL) is perfectly sufficient.

To build on your understanding of these information security building blocks, you need to understand how the discipline of cryptography is applied to distributed messages. The following sections cover the shared key technologies and then cover public key technologies.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020