The OpenSSH client has a lot of very powerful features for tunneling applications through a SSH connections and is one of my favorite tools for quick-and-dirty network plumbing tasks. It can be very useful for fixing/bypassing connectivity issues (caused by NATs, firewalls), accessing internal networks. This post is an overview of the different tunneling options available in OpenSSH. This is inteded as a reference to use when I am explaining (every so often) how to use SSH for tunneling.
Some notes about how TLS v1.3 works. This is a follow-up of the previous episode about TLS v1.2. As before, the goal is to have a high-level overview about how the protocol works, what is the role of the different messages and be able to understand (and debug) a network traffic dump.
Some notes about how TLS v1.2 (Transport Layer Security) works. The goal explain what is going on in a network traffic dump, the role of the different TLS extensions, the impact of the different cipher suites on security, etc. It includes several diagrams and many references.
The Diffie-Hellman (DH) key exchange (and variants thereof) is widely used in many protocols (such as TLS, SSH, IKE (IPSec), Signal, etc.) to bootstrap some symmetric key material which may then be used to secure communication channel between two parties. This introduction focuses on the different ways the DH key exchange is used in practice in several protocols (especially TLS) and the impact of these different approaches on the security. This is intended as a prelude for the upcoming next episodes about how TLS works.
This post gives simple explanations of how UPnP (Universal Plug-and-Play) works, especially with the goal of testing the security devices such as routers, smart TVs, etc.
This post describes different software components involved in host name resolutions and DNS configuration on GNU/Linux systems. It consists of a diagram and some accompanying explanations. The goal is to give some pointers and references to understand how to troubleshoot host name/DNS resolution problems and configuration problems on GNU/Linux systems.