Understanding the TLS Handshake: Unlocking the Mystery Behind That Secure Padlock 🔒

In this article, we’re diving deep into the intricate process that occurs between you and the website you are accessing to obtain that reassuring secure padlock in your browser. This essential element of online security, known as the TLS Handshake, plays a crucial role in establishing a secure connection.

To make this exploration clearer, it may be beneficial to reference a specific infographic that visualizes these steps. If you’d like to follow along, you can find it here.

Let’s clarify what we aim to achieve with SSL/TLS:

1. Authentication: Ensuring that the server is indeed who it claims to be.
2. Session Key Establishment: Creating keys that will secure the data exchanged in the session.

Important Concepts to Know

Before we delve into the handshake process itself, it’s imperative to differentiate between a Record and a Packet. A record is a building block of the TLS handshake, while a packet is a means of transmitting data over the network. Multiple records can fit inside a single packet, and vice versa.

Additionally, having a basic understanding of the following cryptography concepts will greatly enhance your comprehension of the TLS Handshake:

• Hashing
• MACs and HMACs
• Encryption

With these fundamentals in place, let’s unravel the various records that compose the TLS Handshake.

Step 1: Client Hello

The TLS Handshake initiates with a message from the client (your web browser) known as the Client Hello. This message contains five critical components:

1. SSL Version
2. Random Number
3. Session ID
4. Cipher Suites
5. Extensions

Each of these fields serves a purpose in achieving the handshake’s goals.

SSL Version

The client indicates the highest version of SSL it supports, such as TLS 1.2 or TLS 1.3. The server will respond with its supported version, and both will proceed with the