This part of the book deals exclusively with using the X.509 certificates in different services. If you've followed the cookbook up until now, finally you can put that X.509 infrastructure to some good use.

Using X.509 in services is not for the faint of heart. You will find yourself running into poor or clumsy implementations which will leave you desiring for more. Nevertheless, applying the PKI into your user authentication will greatly increase the security of your systems. Just be ready to face a couple of inconveniences along the way. In addition, since this cookbook covers only Free Software, you will find it quite rewarding if you invest at least a little time in trying to improve some project's handling of X.509, therefore I'd like to encourage you to take active role in helping bridge the gap between Free Software and X.509.

The services that will be covered here will range from simple ones, like authenticating onto a system, across mail servers, back-up solutions, and a plethora of others. A couple of approaches will also be covered where it's possible to achieve the same functionality with a different set-up.

The guide will cover both the quirks and set-up steps for the server-side applications as well as the client-applications.