Understanding the TLS Handshake: Securing Your Online Connections 🔒
In this blog post, we will take an in-depth look at the TLS Handshake—the crucial sequence of events that occurs every time you connect to a secure website. This process is what enables your browser to display that reassuring padlock icon, indicating a secure connection.
To enhance your understanding, I recommend opening the following infographic in a new tab: TLS Handshake Infographic. This image visually maps out the communication between your web browser (the Client) and the website’s server as they establish a TLS session.
The Objective of SSL/TLS
Before we dive into the details of the handshake, it’s important to establish the primary goals of SSL/TLS:
- Authentication: Ensuring that the server is who it claims to be.
- Secured Connections: Establishing session keys that safeguard the data exchanged between the Client and the Server.
While the details can get technical, understanding these goals will help you appreciate what’s happening behind the scenes.
Clarifying Terms
Records vs. Packets: Each line in the accompanying infographic represents a “Record” within the TLS handshake, which is distinct from a Packet. Multiple Records can fit into a single Packet or vice versa, so it’s worth keeping this differentiation in mind.
Additionally, familiarity with some cryptographic concepts will be beneficial as we explore the handshake. These include:
- Hashing
- MACs and HMACs
- Encryption
If you’re not already comfortable with these concepts, check out the suggested videos linked above to build your foundational knowledge.
1️⃣ The Client Hello
The TLS handshake initiates with the Client sending a Client Hello message, which includes several key fields:
- SSL Version
- Random Number
- Session ID
- Cipher Suites
- Extensions
1️⃣.1 SSL Version
The Client communicates the highest SSL/TLS version it supports, such as SSL 3.0, TLS 1.0, up to TLS 1.3. The Server responds similarly, and the highest mutually supported version is selected.
1️⃣.2 Random Number
A 32-byte random number generated by the Client adds entropy
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Thank you for sharing this detailed overview of the TLS handshake process. Understanding the intricacies of SSL/TLS is essential for maintaining secure web environments. If you’re encountering issues with the TLS handshake on your WordPress site, here are some troubleshooting steps you might find helpful: