What Is SSL Offloading?

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SSL offloading is a solution used by some businesses to minimise latency and demand on their servers.

You may have noticed as a website user that some websites become sluggish when a large number of users visit them at the same time. Entertainment websites (when a new episode of a hit show airs), news channel websites (during elections), sports websites (during sporting events and competitions), and so on.

But did you know that if your website receives more traffic than normal, the same thing can happen? An SSL/TLS certificate you installed on the server is one of the causes of this latency. Because of security concerns, you can’t (and shouldn’t) delete it, however you can speed up the server by incorporating SSL offloading into your processes.

We’ll look at how a standard SSL/TLS link works and how SSL offloading can help boost site efficiency in this article. We’ll also go through the different forms of SSL offloading, as well as their benefits and drawbacks, so you can determine if it’s the right technology for your website.

What is SSL Offloading?

The responsibility of encryption and decryption is lifted off the server’s metaphorical hands with SSL offloading. Between the browser (client) and the server is a separate SSL proxy device. The application-specific integrated circuit (ASIC) processor, also known as a proxy server or a load balancer, is the SSL offloading unit. They’re made to perform SSL termination and/or SSL bridging using the stable SSL/TLS protocol, which reduces the server’s operational load.

The client sends encrypted traffic to the load balancer. It decrypts the information and sends the unencrypted information to the server. Before sending data to the server, the system can inspect incoming HTTPS traffic, filter malware (if any), and re-encrypt the data.

A firewall, a special programme, or even a hardware device may serve as a load balancer. The following are some of the most well-known SSL load balancer providers:

  • F5,
  • HAProxy,
  • Cloudflare,
  • Nginx,
  • Kemp,
  • loadbalancer.org, and
  • Manage Engine.

How a Regular SSL Connection Is Made Without SSL Offloading

You may be wondering why SSL offloading is needed now that you have a basic understanding of the mechanism. To comprehend this, you must first comprehend how an SSL certificate functions. So, let’s start from the beginning:

  • When a user visits a website, the browser attempts to create an HTTPS link by performing the SSL/TLS handshake. It generates a session key, which is then encrypted with the website’s public key.
  • The website’s server receives this encrypted session key. The website’s private key is then used by the server to decrypt it.
  • Each website has a collection of public and private keys that are exclusive to it. These pairs are mathematically linked in such a way that data encrypted with a public key can only be decrypted with the private key that corresponds to it.
  • This session key is now used to encrypt and decrypt data sent between the browser and the server for the duration of the session.

The Importance of SSL Offloading

With the RSA algorithm, both the public and private keys can be 2048 bits long. It offers strong security, but it’s bulky and sluggish when it comes to encryption and decryption.

The session key will be capable of 256-bit encryption. While it is faster than 2048-bit keys, as more users want to access a website at the same time, the server must deal with multiple session keys and encryption/decryption requests at the same time.

This job is processor-intensive and makes extensive use of the server’s resources. As a result, the server becomes overworked and sluggish. The principle of SSL offloading was implemented in the industry to reduce the encryption/decryption burden on servers.

Note: To replace the 2048-bit RSA key, the latest elliptic curve cryptography (ECC) key has been introduced into the market. With a smaller key size, it provides the same degree of protection. However, only a few SSL certificates and platforms currently support it.

How Does SSL Offloading Work?

SSL offloading is implemented by inserting a separate system — referred to as a load balancer — between the browser and the server to perform encryption and decryption tasks. A new SSL certificate is not needed by the load balancer. It performs the task by using the server’s existing SSL certificate and its private key.

SSL termination and SSL bridging are the two methods of SSL offloading. Let’s look at all of these styles and their benefits and drawbacks.

SSL Termination

SSL termination, as a form of SSL offloading, is basically a mechanism that aids in the speeding up of the decryption process. It accomplishes this by establishing a secure, encrypted HTTPS connection between the client and the load balancer, and then connecting the load balancer to the web server via the insecure HTTP protocol.

The relation between the load balancer and the client will be encrypted. However, data transfer between the load balancer and the server, both incoming and outgoing, will remain unencrypted.

This is how it works:

  • The browser and the server are both linked by a load balancer.
  • The session key is provided between the browser and the load balancer using the website’s public and private keys when the browser tries to create an SSL/TLS link.
  • The load balancer system receives all of the data that has been encrypted by the browser first.
  • The load balancer decrypts the data and sends the unencrypted data to the server using the symmetric session key.
  • As a result, the data is sent in plaintext, and the server does not need to decode it.
  • The load balancer receives the answer from the server in plaintext.
  • The load balancer encrypts the unencrypted data and sends it to the client using the session key.
  • Using the same session key, the client decrypts the data.

Pros of SSL Termination:

  • The server doesn’t have to encrypt and decrypt any of the data that comes in and goes out. That is how the workload is reduced and computing overhead is reduced.
  • It aids businesses in increasing the speed of their servers.
  • SSL termination is an extremely successful tool for websites that do not handle confidential information from users. Blogs, authoritative pages (such as Wikipedia), and media sharing websites are only a few examples (such as YouTube, Pexels, etc.).

Cons of SSL Termination:

  • Data theft, session hijacking, and man-in-the-middle (MitM) attacks are all possible because the traffic between the load-balancer and the server is not encrypted. In a sense, the SSL certificate’s function is defeated because the encryption is lost in the middle of the operation.
  • The load balancer tool and the server must share the private key. It’s a dangerous activity.
  • If the HTTPS session between a load balancer and the server is compromised, clients will not receive any warnings. As a result, it deceives web users into thinking their data is more reliable than it really is.
  • When all of your data is exposed to a third-party load balancer network, an aspect of secrecy and privacy can be lost.

SSL Bridging

SSL termination isn’t suitable for websites that handle confidential data from users, such as personal information, credit card numbers, health information, military information, tax information, and so on. These types of websites are sometimes capable of handling a significant amount of HTTPS traffic. They become slower, however, as they are actively dealing with malware and infected data from the client. SSL bridging, another SSL offloading process, is more efficient in these situations than SSL termination.

SSL bridging, including SSL termination, uses a load balancer to link a client and a server.

When a client sends encrypted data to the load balancer via HTTPS, the data is decrypted. The SSL inspection task is then completed. For all HTTPS traffic, the load balancer conducts deep packet inspection, and if it detects anything unusual, it blocks it. It’s similar to a man-in-the-middle attack, but instead of cheating users, it’s used to defend them!

The load balancer then rewrites and re-encrypts the information before sending it to the server, rather than sending it in plaintext. As a result, the data is encrypted and stable throughout the entire journey. The server, as you may have guessed, also needs to go through the encryption and decryption process.

The SSL load balancer filters out viruses, spyware, and other types of malware coming from the client in SSL bridging.

Pros of SSL Bridging

Since the data is encrypted during the transmission phase, from the client to the load balancer, and from the load balancer to the server, data protection is not jeopardised.
It protects the server from SQL injections, distributed denial of service (DDoS) attacks, and cross-site request forgeries, which are the most popular web-application attacks.

Cons of SSL Bridging

The re-writing mechanism is the most significant downside of SSL bridging. If the load balancer’s artificial intelligence (AI) detects something unusual, it will be given the authority to inspect and change the client data. It re-encrypts and only sends the content that it considers secure. As a result, for all incoming data, you will depend on the load balancer’s AI. If the load balancer’s AI has a false positive (i.e., it incorrectly considers safe traffic to be malicious) and blocks it, you’ll also miss the relevant (and safe) traffic.
The server’s load for encryption and decryption does not decrease.

A Final Thought

In today’s highly competitive environment, a slower website has no location. If your website’s content takes more than a few seconds to load, visitors will leave and go to another site, probably one of your competitors’. At the same time, removing an SSL certificate from your website exposes the domain, as well as any sensitive data it gathers, to cyber attacks.

With SSL offloading technology, you get the best of all worlds when it comes to risks and circumstances. You gain increased speed without jeopardising protection. SSL offloading technology, on the other hand, has bugs and may put a website’s protection at risk. Since the same load balancer cannot perform SSL termination and SSL bridging at the same time, you must choose which option is best for your server after reading the benefits and drawbacks of both forms of SSL offloading.

Melina Richardson is a Cyber Security Enthusiast, Security Blogger, Technical Editor, Certified Ethical Hacker, Author at Cybers Guards & w-se. Previously, he worked as a security news reporter.