Understanding the TLS Handshake: How Your Browser Secures Your Connection đź”’
In the digital world where online safety is a priority, the TLS (Transport Layer Security) handshake is a crucial step in establishing a secure connection between your web browser and the website you are visiting. This process is what ultimately grants you the reassuring padlock icon in your browser, signifying that your connection is secure. In this post, we will explore all the intricate details of what unfolds during a TLS handshake, drawing upon a helpful infographic for reference.
For a visual aid, feel free to check out the infographic here. It might be beneficial to keep this image open in a separate tab as we delve into the handshake process.
The Purpose of SSL/TLS
Before we dive into the particulars of the handshake, it’s essential to understand the two primary objectives of SSL/TLS:
- Authentication: Verifying that the server is genuinely who it claims to be.
- Session Key Establishment: Creating session keys that will encrypt the data transmitted during the session.
Important Concepts to Understand
To fully grasp how the TLS handshake operates, familiarize yourself with these key cryptographic concepts:
- Hashing
- Message Authentication Codes (MACs) and Hash-based MACs (HMACs)
- Encryption
We won’t be delving into the complexities of these terms here, but additional resources are available should you seek further understanding.
The Handshake Journey
1. Client Hello
The initial step in the TLS handshake is initiated by the client, your web browser, sending a “Client Hello” message. This message contains five vital components:
- SSL Version
- Random Number
- Session ID
- Cipher Suites
- Extensions
These components serve distinct purposes crucial to the handshake’s success.
Key Components Explained
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SSL Version: The client indicates the highest version of the SSL/TLS protocol it supports. The server will reply with the highest version both parties can agree upon, primarily focusing on TLS 1.2 and TLS 1.3, the only secure versions in use today.
-
Random Number: The client generates a 32-byte random number, contributing to the security of the shared session keys by adding “entropy
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