13.7 Summary

In this chapter, we looked at the TLS handshake protocol from a bird’s-eye view, with the help of TLS client and server state machines. The state machines illustrate how the TLS protocol works on a higher level. In addition, we covered the Finished message and several post-handshake messages in more detail.

We also learned how to use OpenSSL, a popular cryptography and TLS toolkit, and, especially, the s˙client OpenSSL tool to experiment with TLS. We discussed how to install and how to use s˙client and presented several experiments that you can reproduce and enhance on your own. These experiments allow you to observe TLS at work and take a close look at cryptographic mechanisms and TLS features used in the handshake protocol.

This chapter concludes the second part of the book. In the next part, we will study the TLS record protocol. The record protocol protects application data using shared secret keys established during the TLS handshake. We will start...