Differences between TLS 1.2 and 1.3 – What makes them different?

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You're busy setting up a secure connection for a new web server and need to choose between two protocols: TLS 1.2 vs. TLS 1.3 . While they may seem interchangeable, their differences can have a significant impact on your server's performance and security.

For example, TLS 1.3 has an improved handshake process that speeds up secure connections. But that's just the tip of the iceberg. Let's dive a little deeper into the technical details of the two protocols so you understand the differences between TLS 1.2 and 1.3 .

Table of contents

What is TLS 1.2 handshake?
What is TLS 1.3 handshake?
What is the difference between TLS 1.2 and 1.3?
What is TLS 1.2 handshake?
To better understand the TLS 1.2 handshake , let's look at how the client and server establish a secure connection. The first step is initiation, where the client sends a 'Client Hello' message to the server. This message contains the client's TLS (Transport Layer Security) version, cipher suites , and a random byte string known as Client Random.

In response, the server sends a 'Server Hello' message. This message contains the protocol version selected by the server, a set of ciphers, and a Server Random byte string. The server then sends messages about the exchange of server certificates and keys.

The client then checks the server's certificate with mobile app development service the Certificate Authority (CA) . If the check is successful, the client sends a Client Key Exchange message that contains the pre-master secret encrypted with the server's public key .

The client and server then use the pre-master secret and the corresponding random byte strings to generate the same symmetric session key . The client then sends a 'Change Cipher Spec' message, indicating that it will encrypt all further communications using the session key.

To complete the TLS handshake , the client sends an 'Encrypted Handshake Message' to confirm that the session key has been successfully established. The server will also send a similar message to the client.




What is TLS 1.3 handshake?
TLS 1.3 eliminates several roundtrips, reducing the number of rounds between the client and server from two to one by combining the client and server hello messages. The client sends a “Client Hello” with the cipher suites it supports and a random number. Instead of waiting for the server to send a hello, the client immediately sends its key resource, the predicted cipher, and the server’s certificate.

This optimized process, known as 'Zero Round Trip Time' or 0-RTT, not only speeds up the handshake, but also significantly improves overall connection time. TLS 1.3 also introduced the concept of 'Early Data', which allows the client to send some data in the first round, further improving performance.

From a security perspective, the TLS 1.3 handshake increases privacy by encrypting much of the process . In contrast, TLS 1.2 exposes some details about the server and client in the clear, which creates potential security risks.

What is the difference between TLS 1.2 and 1.3?
The key difference between TLS 1.2 and 1.3 is the handshake process itself. Later versions, such as TLS 1.3, make the handshake simpler and faster by reducing the round-trip time—just one of many improvements that improve performance and security. Understanding the key differences between TLS 1.3 and 1.2 will help you upgrade to the latest 1.3 version.

Round trip travel time (RTT)
Round Trip Time (RTT) is the time it takes for a signal to travel from the sender to the receiver and back. In protocols like TLS, RTT is critical because it directly affects how quickly a user's browser and the website server can establish a secure connection.

In TLS 1.2, when your browser connects to a secure website, the handshake process requires two rounds between the client (your browser) and the server before they can begin securely exchanging data.