The applications of today depend more and more on secure communication channels. For most internet applications the TLS protocol (still mostly referred to as SSL) is providing the secure channel to communicate over. To be able to troubleshoot problems with Applications that use (mutual) TLS, one must understand how TLS sessions are set up, how certificates and certificate authorities come into play and how you can look inside the encrypted traffic to analyse the (cleartext) application data. In this session you will gain a better understanding of the operation of the TLS protocol and more importantly, you will learn how to troubleshoot TLS based communications when things don't work as expected.