Understanding the 3-Way Handshake & TLS: The Foundation of Secure Communication

Introduction

When you visit a website, send a message, or make an online payment, your data doesn’t just travel blindly across the internet. It follows structured protocols that ensure reliability and security. Two key concepts behind this are:

1. The 3-Way Handshake (used in TCP to establish a connection)

2. Transport Layer Security (TLS) (used to encrypt and secure communication)

In this blog, we’ll break down how these two work together to form the backbone of secure web communication.

What is the 3-Way Handshake?

The 3-Way Handshake is the process TCP (Transmission Control Protocol) uses to establish a reliable connection between a client and a server.

Steps of the 3-Way Handshake

1️⃣ SYN (Synchronize) → The client sends a SYN request to the server to initiate a connection.

2️⃣ SYN-ACK (Synchronize-Acknowledge) → The server responds with SYN-ACK, acknowledging the request.

3️⃣ ACK (Acknowledge) → The client sends an ACK, confirming the connection.

✅ Connection Established

The 3-way handshake ensures that both parties are ready for communication and prevents data loss.

What is TLS and How Does It Work?

While TCP ensures a reliable connection, it does not encrypt the data being transmitted. That’s where TLS (Transport Layer Security) comes in.

TLS Handshake: Steps for Secure Communication

1️⃣ Client Hello → The client sends a request to the server, listing supported TLS versions & encryption algorithms.

2️⃣ Server Hello → The server picks a TLS version & encryption method, then sends its TLS certificate.

3️⃣ Certificate Validation → The client verifies the server’s certificate authority (CA) to ensure it’s legitimate.

4️⃣ Key Exchange → The client and server agree on a session key for encryption.

5️⃣ Secure Communication Begins → All data is encrypted using this session key.

How the 3-Way Handshake and TLS Work Together

When you open a secure website (https://), both TCP and TLS work together:

1️⃣ TCP 3-Way Handshake establishes a reliable connection.

2️⃣ TLS Handshake secures the communication by encrypting the data.

🔹Without TCP, data transfer could be unreliable. 🔹 Without TLS, data could be intercepted by hackers.

That’s why both are crucial for modern web security.

Conclusion

The 3-Way Handshake and TLS are fundamental to secure web communication. TCP ensures connection reliability, while TLS provides encryption and authentication. Together, they make the internet safer for everyone.