Even if you are not running a mainframe you probably have some old applications which you still need and whose code you cannot lift into the present (technology-wise). This is something you need to address. Despite decades of security research and authentication standards there’s still a vast amount of systems with custom solutions and embedded user databases. Such systems are typically hard to securely integrate with others. We analysed an existing system of an organisation with approximately 12.000 sensitive user data sets and uncovered severe vulnerabilities in their approach. We developed a minimal, secure Single-Sign-On-Solution and demonstrated the feasibility of implementing both a minimal Identity Provider and a minimal Service Provider with only a few lines of code. We provided a simple blueprint for an Identity Provider and an easy to use Service Provider Library. Therefore this organisation is now able to integrate arbitrary web based systems. Moreover, others can follow the proposed approach and tailor similar solutions at low cost.
At DeepSec 2015 Bernhard Göschlberger and Sebastian Göttfert presented a case where you can study how to deal with legacy applications.