Understanding secure encryption with OpenVPN

The security of a network is fundamentally important, especially when it comes to sensitive data. OpenVPN offers various options for encryption, which differ in application and security. In this guide, I will introduce you to the different encryption methods, explain how they differ from each other, and how you can use them in your OpenVPN installation.

Main insights

• There are two main types of encryption in OpenVPN: the use of static keys and certificate-based authentication.
• Static keys use a symmetric method, while certificate-based authentication is based on asymmetric methods.
• Each method has its advantages and disadvantages, affecting how secure and simple key management is.

Step-by-step guide to encryption with OpenVPN

Basics of encryption

First, it is important to understand what encryption actually means. In a VPN (Virtual Private Network), the communication between your client and the server is encrypted to ensure that third parties cannot access the transmitted data. OpenVPN offers two main methods: the use of static keys and the use of certificates.

Static keys (PSK)

The use of a static key, also known as a Pre-Shared Key (PSK), is a method based on symmetric encryption. Here, a key is used to both encrypt and decrypt the data. This means that the same key is used on both the client and server sides. The disadvantage of this method is that the key must not be changed or compromised, as this could jeopardize the entire communication.

To ensure security, the static key must be distributed to all participants in the communication. Suppose you have 100 contacts, and the key is deemed insecure. Then you must resend this key to all 100 contacts, which poses a great security risk. An important question that arises here is: How can you securely distribute the key without it being intercepted by third parties?

Certificate-based authentication

Certificate-based authentication represents the safer option. This method utilizes asymmetric encryption to protect the connection. It uses public and private keys as well as X.509 certificates. Unlike the use of a static key, it is less problematic if the public key is intercepted here. The private key remains confidential and is not sent over the network.

The OpenVPN toolkit includes tools for generating your own keys, allowing you to create your certificates. This makes it easier to maintain authentication and ensure that all participants are properly verified. However, this method also brings a higher complexity and more configuration effort.

Summary – Understanding and setting up encryption with OpenVPN

In this guide, you have learned about the different encryption methods in OpenVPN. Understanding static keys and certificate-based authentication is fundamental to ensuring a secure VPN connection. You have learned that the choice of encryption method depends on both security requirements and management efforts.