Understanding the TLS Handshake: Unlocking the Secrets of Secure Connections 🔒
When you browse the web, have you ever noticed that little padlock icon? It represents a secure connection, made possible through a complex yet fascinating process known as the TLS handshake. In this post, we will demystify the handshake, explaining everything that occurs between your browser and the website you visit to ensure your data remains confidential and secure.
To guide our exploration, I recommend keeping an informative infographic handy, which illustrates the various exchanges that take place during a TLS session. You can find it here.
The Basics of SSL/TLS Handshake
Before we dive deep into the handshake details, it’s essential to understand that the primary objectives of SSL/TLS protocols are twofold:
- Authentication: Ensuring the server is indeed who it claims to be.
- Confidentiality: Establishing session keys to protect the data exchanged during the session.
Understanding Records vs. Packets
In the context of the TLS handshake, a “record” refers to a message containing essential information. It’s important to note that a record does not directly equate to a packet. Frequently, multiple records can fit into a single packet, or conversely, a single record may require multiple packets for transmission.
Key Cryptographic Concepts
Before we begin breaking down the handshake, it’s useful to familiarize yourself with some core cryptographic concepts:
While we won’t dive into these topics in great detail here, understanding them will enhance your comprehension of the TLS handshake process.
The Handshake Process
1️⃣ Client Hello
The handshake process commences with the Client Hello message sent from your web browser. This message contains five crucial fields:
- SSL Version: The highest SSL/TLS version the client supports (e.g., SSL 3.0, TLS 1.2).
-
Random Number: A 32-byte piece of random data for entropy in session key generation.
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