What is SSL/TLS Handshake? Learn the Process, Work and Importance

Introduction

Living in the age of active use of the internet and other computer-based activities, it is crucial to protect our interactions as well as our identities in the virtual space. Starting from sensitive money transactions like online banking, purchases over the internet, or receiving personal information through the web, our data need protection from malicious parties.

It is here that SSL/TLS handshake comes in handy to erring as a digital doorman responsible for ensuring the security of our online interactions.

The SSL/TLS handshake is a very complex request-response mechanism that acts as a middleman by creating a secure, encrypted link between a client (like a web browser) and the server, which is likened to building a wall around our information.

Through the authentication of the server, determining the encryption techniques to be used and the symmetric keys, plus the validation of the completeness and accuracy of messages exchanged, this process enhances the privacy and security of our Online interactions from the threat posed by intruders and hackers.

What Is an SSL/TLS Handshake?

The SSL/TLS handshake is a procedure for starting a connection on the computer for secure data transfer over the internet. It includes several procedures aimed at ensuring the identity of the server, the choice of the encryption algorithms and the keys, and the non-tampering of data exchanged within the protocol.

This handshake process makes certain that the communication that you are having on the internet, whether is in websites that you are visiting, things that you are buying online, or even secure details that you are accessing, are safe.

What Is an SSL Handshake?

It stands for Secure Sockets Layer. This is simply the mechanism that was utilized to start the procedure of developing a secure connection between a web server and a browser. It turned out to be the predecessor of TLS (Transport Layer Security).

Even though both protocols are used to enhance security in internet communication, TLS is more upgraded than SSL and is widely encouraged. It enlarges the security of the SSL protocol establishing itself and addresses some of the weaknesses identified by SSL.

When does a TLS Handshake Occur?

TLS connection happens every time there is a client-server interaction, wherein the client wishes to connect to a secure server, for instance, a website.

This typically happens when you access a website that starts with “https:// It is used whenever you want to deliver a highly confidential message or materials that cannot be accessed by third parties or even when you are sharing some important details like login details, financial details, or even personal details.

What Happens During a TLS Handshake?

The TLS handshake refers to a bit more comprehensive process in which the client and server exchange messages to establish a secure connection.

Here’s a breakdown of the steps involved:

Step 1. Client Hello:

The encryption process starts with the client sending a ‘Client Hello’ message to the server as a beginning to the handshake process. This message contains the list of cipher suites supported by the client (encryption algorithms), a list of supported compression methods, and a random number used as a seed when generating keys.

Step 2. Server Hello:

The client sends a “Client Hello” message, which includes a random number and a session ID, as well as the proposed settings for cipher suite and compression. It is also used with its digital certificate, as well as a random number to generate a key.

Step 3. Certificate Verification:

To enable this, the client checks for and authenticates the server’s digital certificate by obtaining it from the Certificate Authority (CA). This step is useful in avoiding the cases where an attacker may disconnect those two parties and connect himself to the flow.

Step 4. Key Exchange:

This is designed to run between the client and the server and data is exchanged in encrypted messages to produce a shared secret key. This type of key is employed during the process of the establishment of a secured session for the encryption as well as decryption of information.

Step 5. Finished:

After the mutual authentication is accomplished as well as the session key, the client and the server exchange figures termed as “Finished”. This assures that the handshake has been completed and that from that point onward, data transfer can ensue safely.

TLS Handshake (for Versions 1.2 and Below)

For TLS versions 1. Downwards to 2, the key exchange step is the use of asymmetric cryptography such as RSA for key exchange.

This is followed by the use of encryption algorithms such as the Advanced Encryption Standard (AES) in deriving symmetric keys for use in key exchange protocol to agree on a shared secret key.

The application of asymmetric encryption for initial key exchange is reasonable because it serves the purpose of securing keys that are transmitted over an insecure channel. However, symmetric encryption algorithms provide more efficiency and speed to encrypt large amounts of data while the secure session is certainly being established.

Understanding the Key Exchange Process

The important one is the key exchange procedure which is a component in the SSL/TLS handshake process.

It is a two-way process whereby the client and the server engage in an exchange of messages with the intended purpose of deriving a shared secret key that is going to be used for encrypting the data during the sessions that have been deemed to be secure.

In TLS versions 1.2 and below, the key exchange process typically involves the following steps:

Step 1. Client Key Exchange: The client creates the pre-master secret key through the mathematical algorithms namely the asymmetric key algorithm like RSA and then sends the pre-master secret key enclosed with the encrypted form of the server’s public key.

Step 2. Server Key Exchange: The pre-master secret key is decrypted using the server’s private key.

Step 3. Master Secret Generation: Both the client and server side share the pre-master secret key and random numbers that have been sent during the handshake phase to generate the master secret key.

Step 4. Session Key Derivation: The master secret key can then be used to produce session keys that can be used for enciphering and deciphering data during the protected and secure session.

This key exchange process helps make sure that the shared secret key is never to be sent in the plaintext form through the existing channel hence reducing the risk of the same being intercepted by the third party.

Secure Renegotiation in TLS

This is the other standard model within the TLS protocol that can be used to carry a secure renegotiation that lets the client and server renegotiate the keys or the cipher suites during an already secured session.

This feature is handy when there is a need to make changes in the parameters depending on several aspects of characteristics including compliance with different standards or a desire to use different levels of encryption.

The TLS reconnect process entails a significantly similar handshake procedure to the initial process, although with some enhancements for efficiency. This technique implies the exchange of two new random numbers, a certificate (if it is necessary), and agreement on new parameters of the encryption.

Renegotiation is an important extent for TLS protocol because it allows for ongoing security to continue during the lifetime of the connection whilst healing of latter for new keying by minimizing the cost of initiating of new SSL/TLS session.

Notably, it is important to point out that the renegotiation itself may also be open for certain types of attacks, such as a denial of service (DoS) attack, in case the implementation of the concept is flawed. hence the need to adhere to different standards and guidelines in achieving secure renegotiation in TLS.

What Is Different About a Handshake in TLS 1.3?

TLS 1.3, the latest version of the protocol, introduces several improvements to enhance security and performance:

Reduced Handshake Steps: The handshake process in TLS 1.3 has fewer steps, making it more efficient and reducing the risk of potential vulnerabilities.

Encrypted Server Certificate: In TLS 1.3, the server’s certificate is encrypted, providing an additional layer of protection against eavesdropping and man-in-the-middle attacks.

Improved Key Exchange: TLS 1.3 uses more secure key exchange algorithms, such as Elliptic Curve Diffie-Hellman (ECDHE), which provide better protection against quantum computing attacks.

Deprecated Insecure Algorithms: TLS 1.3 has deprecated support for insecure algorithms like RSA key exchange, static Diffie-Hellman, and SHA-1 hashing, further enhancing security.

Zero Round-Trip Time (0-RTT) Resumption: TLS 1.3 introduces a feature called 0-RTT Resumption, which allows clients to resume a previous secure session without performing a full handshake. This improves performance and reduces latency for subsequent connections.

Perfect Forward Secrecy (PFS): TLS 1.3 enforces Perfect Forward Secrecy (PFS), which means that even if the server’s long-term private key is compromised, past communication sessions remain secure and unaffected.

The improvements in TLS 1.3 make it more secure, efficient, and resilient against various types of attacks, including those that may be enabled by the advent of quantum computing.

Importance of the SSL/TLS Handshake

The SSL/TLS handshake plays a crucial role in ensuring the security and privacy of online communications. It provides several key benefits:

Encryption:

It makes a connection between the client and server and ensures that no other program can read that information because it uses a coded system that has been decoded by both the client and server.

Authentication:

Besides confirming the identity of the server, the handshake involves the exchange of cookies and other values by the server and allows the client to confirm that it is communicating with the intended server and not an imposter.

Integrity:

The Handshake process itself has some controls built into it that guarantee the originality of data transmitted in the agreement.

Privacy:

Methods of data encryption used during the secured session are a measure of concealing the information so that it would be received and understood only by the parties involved.

Compliance:

The integration of the SSL/TLS handshake protocols acts as a possible solution that can assist Organizations in adhering to specific data protection statutes and diverse benchmark guidelines that are in existence including; GDPR, HIPAA, and PCI-DSS.

Trust and Reputation:

Implementing SSL/TLS handshake protocols that ensure confidentiality of online communications can be a mark of reacting to the organization’s data security policies and helps in gaining the customer and stakeholders’ confidence and belief.

If an SSL/TLS handshake does not take place, the transmission of data over the Internet is not secure and information can be intercepted, modified as well, or even masqueraded by an attacker causing a threat to secure Internet communications.

These risks may result in monetary losses, loss of company image, and even lead to the emergence of legal repercussions.

Conclusion:

Strengthen your organization’s protection of communications over the Internet by updating your TLS version to the current version and it is recommended that proper encryption protocols should be put into practice.

Secure your business and its reputation, build and retain the confidence of buyers and investors, and abide by the laws and standards of your fields.