Understanding the TLS Handshake: The Journey to Your Secure Connection 🔒
When you browse the internet, you often see a little padlock symbol indicating that your connection to a website is secure. But what exactly goes on behind the scenes to earn that lock? Today, we will delve into the TLS handshake, the critical series of interactions between your web browser and the server hosting the website, ensuring a secure connection.
To enhance your understanding, consider keeping this infographic handy as we navigate through the handshake process.
Setting the Stage
Before diving into the handshake itself, let’s clarify the two primary objectives of SSL/TLS:
- ✅ Authenticate the Server: Confirm the server’s identity to ensure it is who it claims to be.
- ✅ Establish Session Keys: Create keys that will secure the data being transferred.
As we explore each step, here are a couple of key concepts to keep in mind:
Records vs. Packets
Each communication step in the TLS handshake is referred to as a “record,” which should not be confused with a “packet.” Multiple records can be sent in a single packet, and conversely, a single record might require several packets for transmission.
Cryptographic Foundations
A basic understanding of certain cryptographic principles will enhance your grasp of the TLS handshake, including:
- Hashing
- Message Authentication Codes (MACs) and HMACs
- Encryption
Though we won’t delve deep into these concepts here, feel free to explore linked resources for additional context.
The Handshake Breakdown
Now, let’s examine each stage of the TLS handshake:
1️⃣ Client Hello
The process begins with the Client Hello message from your web browser. This message incorporates five key fields:
- SSL Version: Indicates the highest SSL/TLS version supported by the client (e.g., SSL 3.0, TLS 1.2).
- Random Number: A 32-byte random value created by the client for use in key generation.
- Session ID: Used for session resumption (we’ll discuss this later).
- Cipher Suites: A list of supported encryption algorithms for secure communication.
- Extensions: Optional features that enhance the handshake process.
2️⃣ server Hello
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