3-Way Handshake: Is It Secure?

3-Way Handshake: Is It Secure?

 By Charles Joseph | Cybersecurity Advocate
 Last update: November 25, 2023

A 3-Way Handshake is a process used in computing to create a connection between two computers over a network.

The handshake involves three steps.

First, the initial computer sends a request to the second one.

The second then acknowledges the request and sends one of its own.

Finally, the initial computer confirms the second’s request. This process ensures a secure and effective data transmission.

3-Way Handshake Examples

1. Web Browser to Server

When browsing the internet, the 3-Way Handshake is an essential process that happens in the background every time a webpage is loaded. The moment you enter a URL into your browser, the initiation phase of the handshake starts. In this phase, your browser sends a request to establish a connection with the server that hosts the webpage you intend to view.

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Next, the server acknowledges that it has received the request from your browser. To confirm this, the server sends a response back. This acknowledgment from the server is the second step in the 3-Way Handshake.

Finally, your web browser receives the server’s acknowledgment and responds with its own final acknowledgment to the server. This completion of the handshake establishes a secure connection between your browser and the server. Now, the server can deliver the webpage’s content, ranging from text and images to videos and interactive features. This example illustrates how that initially simple act of loading a webpage involves an essential security and reliability process known as the 3-Way Handshake.

2. Email Client to Email Server

In the world of email communication, the 3-Way Handshake plays a critical part. Suppose you’ve crafted an email and hit the “send” button. What happens next is handled by your email client, whether that’s Outlook, Gmail, or another program. It initiates the handshake by sending a connection request to the email server that is meant to dispatch your message.

In the second step of the 3-Way Handshake, the email server acknowledges the connection request from your email client. As a part of its reply, it also sends its own connection request, reaching back to your email client.

The final step of the process is the acknowledgment of the server’s request by your email client. With this completed, a secure connection is established between your email client and the server. It’s through this secured connection that your email can now be safely relayed to the recipient’s server. This demonstrates the integral role the 3-Way Handshake plays in secure email communication.

3. File Transfer

File Transfer Protocol (FTP), a standard networking protocol, relies heavily on the 3-Way Handshake process. Consider a scenario where you need to send a file from a computer located in your office to a remote computer. The first step in this file transfer is the initiation of contact by the sending computer. This is done by sending a connection request to the receiving computer.

In response to the initial connection request, the receiving computer sends an acknowledgment back to the sending computer. As part of this response, it also sends its own connection request. This marked the second stage of the 3-Way Handshake process.

The final stage in the handshake occurs when the sending computer acknowledges the connection request made by the receiving computer. Upon the completion of this step, a secure data transmission route is established between the two computers. Consequently, the file initially intended for transfer can now be securely and effectively transferred. This example portrays how the 3-Way Handshake aids in secure data transfers via FTP.


In conclusion, the 3-Way Handshake is a fundamental process in computing that facilitates the establishment of secure data connections, whether when browsing the web, sending an email, or transferring a file. Its role in assuring a safe and efficient communication between devices underscores its importance in our daily digital interactions.

Key Takeaways

  • The 3-Way Handshake is a secure procedure used to establish connections between devices in a network.
  • It’s a three-step process involving an initiation, an acknowledgment, and a finalizing acknowledgment.
  • This process is crucial in many areas of computing, such as web browsing, email communication, and file transfer.
  • The handshake ensures that data is securely and efficiently transmitted between the communicating parties.
  • Despite being a technical process, it quietly operates in the background of our daily digital activities, securing our online communications.

Related Questions

1. Can the 3-Way Handshake process be targeted by cyberattacks?

Yes, the 3-Way Handshake can be a target of cyberattacks. TCP SYN flood attack is one such example, where the attacker sends a large number of SYN (synchronization) packets to a server in an attempt to consume enough server resources to make the system unresponsive to legitimate traffic.

2. What role does the 3-Way Handshake play in the Transmission Control Protocol (TCP)?

In TCP, the 3-Way Handshake is used to establish a reliable connection. This handshake process ensures that both the sender and receiver are ready for data transmission and allows them to agree on parameters such as sequence numbers and checksum values.

3. Is there an alternative to the 3-Way Handshake?

Yes, there’s an alternative known as the 4-Way Handshake, commonly used in wireless security protocols like WPA and WPA2. Unlike the 3-way Handshake, a 4-way Handshake includes additional steps for authentication and key exchange to further enhance the security of the connection.

4. What happens if the 3-Way Handshake isn’t completed?

If the 3-Way Handshake isn’t completed, the connection between the devices isn’t established. The data to be transmitted can’t be sent, and the communication between the devices fails.

5. What is an ACK in the context of a 3-Way Handshake?

ACK, short for acknowledgment, is a signal sent between devices during the 3-Way Handshake. It confirms that a request or a couple of steps of the handshake have been received and acknowledged, allowing the process to advance to the next stage.

"Amateurs hack systems, professionals hack people."
-- Bruce Schneier, a renown computer security professional