Have you ever wondered how, for example, a browser and a server communicate through the network?
Here’s where the SSL handshake comes into play. In this example, before sharing any data, a browser and a server need to agree on data exchange or to “shake on it”, thus engaging in an SSL handshake. During the handshake, they might need to see each other’s SSL certificates. If, for example, you just started dedicated server renting, you might double-check whether it has the needed SSL certificates.
The thing is that an SSL handshake is vital for establishing a secure connection for your data to be transferred; therefore, it is essential to understand how it works.
What is an SSL handshake?
A handshake is the initial step in the communication between the client and a server; without it, further connection isn’t possible.
At the handshake stage, a client and a server “meet” each other for the first time, and the handshake procedure involves “getting to know each other on a deeper level.”
The critical step of a handshake process is an authentication procedure to confirm the server’s legitimacy. In this procedure, a public key assigned to a server is compared to an SSL certificate associated with it to verify the server’s identity. This step is vital in promoting secure communication. Further, we’ll look in more detail into the steps the SSL handshake procedure consists of.
Why is SSL handshake important?
SSL handshakes promote secure data transfer and protection from third-party data interception. SSL handshakes ensure that only the intended source gets the information transferred.
SSL handshakes work hand-in-hand with SSL certificates, which, in turn, are closely monitored by the relevant authorities and follow the specific protocols for issuing.
This helps prevent unwanted data leaks and security threats and makes it possible to exchange sensitive information safely.
Eventually, SSL handshakes are not just an option feature but a necessary tool to ensure the security of parties involved in digital communication.
The SSL handshake procedure
The steps of the SSL handshake procedure vary based on the SSL version of the client and the server. However, there is a general outline of the process adhered to in all instances.
Step 1: Client’s greeting. A “client hello” message includes the SSL version it wants to use to communicate with the server and specific encryption algorithms (Cipher Suites).
Step 2: Server’s greeting. A ”server hello” message includes its SSL certificates and encryption algorithms it chose from the client’s list; this message might also contain a request for the client’s certificates.
Step 3: Server’s certificate verification. In this step, a client verifies the server’s certificates. This step also includes sending the so-called byte strings, one of which contains a secret key used for further communication.
Step 4: Client’s certificate verification. In this step, a server verifies the client’s certificates if such a request has been made.
Step 5: The client is finished. The “finished” message on the client’s end implies that the client has completed the steps needed to conclude the handshake.
Step 6: The server is finished. The “finished” message on the server’s end implies that the server has completed the steps needed to conclude the handshake.
What happens next is the exchange of data encrypted with a secret key mentioned in Step 3.
Troubleshooting SSL handshake error
Sometimes, users get an SSL Handshake Failed error because the client and the server weren’t able to establish a connection. Now, there could be multiple reasons for this, including:
- Client and server not supporting the same SSL version
- Client and server using different encryption algorithms
- The client’s or server’s certificates are invalid
There can be issues on the client’s side specifically, including:
- The client has the wrong configuration
- The client uses the wrong date and time
- Client protection was insufficient and allowed communication to be intercepted by third parties
There are several methods you can try to resolve the issue.
Setting the correct time and date
Correct time and date are crucial for SSL certificates since they have an expiration date set. Try setting the right time and date and see if it works.
Accessing through another browser
Sometimes, browser settings, extensions, or other browser applications can cause an SSL Handshake Failed error. Try switching to another browser and see if it solves the issue.
Adding a website to allowlist
A firewall can block your request. You could turn off the firewall, but it will leave you vulnerable to security threats. Try adding the website to the allowlist instead.
Updating SSL certificates
You might get the error because the client and the server do not support the same SSL version.
In this case, you should update your browser or update SSL certificates manually.
Checking whether the client and the server use identical Cipher Suites
If the client and the server don’t use identical Cipher Suites, it’s likely to cause an error.
You can compare which Cipher Suites the client and the server are using on the SSL Labs website.
Make sure your SSL certificates are valid
If the SSL certificate has the wrong hostname or is expired, it can cause an SSL Handshake Failed error. You can use online tools to see whether your SSL certificates are valid.