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What is SSL Certificate Encryption Strength? Which Cert Should I Choose?

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Here’s what you need to know about HTTPS encryption strength and how to choose the right certificate for your organization

“What does SSL certificate encryption strength mean?” A lot of people ask this question when venturing into SSL/TLS territory for the first time. It can be quite confusing as many different SSL selling websites show many different encryption strengths for various SSL certificates. But don’t worry, we’re here to help you sort it all out.

In this post, we’ll break down what “SSL encryption strength” means and help you learn how to make an informed decision about the best SSL certificate for your website security. But, before we dive into SSL/HTTPS encryption strength, let’s first understand how SSL encryption works.

How SSL Certificate Encryption Works

As far as the encryption method is concerned, an SSL certificate encrypts the data using the asymmetric encryption method. Asymmetric encryption involves two distinct — yet mathematically related — keys. One of those keys is called a public key and the other is called a private key.

The public key, as the name implies, is publicly available and is used to encrypt the data. The private key, on the other hand, is kept secret and is held on the web server. It’s used to decrypt the data.

The process of establishing a secure connection is called an SSL/TLS handshake. This virtual handshake takes place between the two parties involved in the data communication: the client and the server.

Here’s how the standard SSL/TLS handshake works:

  1. Client Hello: The client initiates the handshake and sends a “hello” message to the server. The message will include supported TLS version, the cipher suites, and a string of random bytes known as the client random.
  2. Server Hello: The server responds to the client’s initiation by sending a message that consists of an SSL/TLS certificate, supported cipher suites, and server random.
  3. Authentication and Pre-Master Key: The client authenticates the server certificate, and it creates the pre-master key for the session, encrypts with the server’s public key and sends the encrypted pre-master key to the server.
  4. Decryption and Master Secret: The server decrypts the pre-master key using its private key and then, both the server and client perform specific steps to generate the master secret with the agreed cipher.
  5. Encryption with Session Key: Both client and server exchange encrypt and decrypt the information using a common key. This key is called a session key, and this method of encryption is called symmetric encryption.

So, What is SSL Certificate Encryption Strength?

Now that you’ve understood (hopefully) how SSL encryption works, let’s dig into what it means when we talk about “encryption strength.” When we talk about encryption strength, we’re actually talking about two different things. There’s the security potential of encryption in terms of what your cipher and hash functions were designed to achieve, and then there’s the actual encryption strength you can achieve based on your server configuration and capabilities.

HTTPS Encryption Strength: Encryption Type

HTTPS is a protocol to communicate securely on an untrustworthy network. The HTTPS encryption uses PKI (Public key infrastructure) type algorithm called Transport Layer Security (TLS).

As we saw in the SSL/TLS handshake, SSL/TLS encryption is done using two methods: asymmetric encryption and symmetric encryption. Asymmetric encryption is used for the purpose of verification of both the parties. Symmetric encryption actually encrypts and decrypts the data. Therefore, whenever you see the term “encryption strength,” it actually refers to the length of the session (symmetric) key that encrypts the data.

But why is it so secure? For starters, no one knows this key except the browser and server, and it’s different for each session. But there’s more to it than that.

HTTPS Encryption Strength: Server Configuration

Most of today’s SSL/TLS certificates offer 256-bit encryption strength. This is great as it’s almost impossible to crack the standard 256-bit cryptographic key. However, as we mentioned earlier, the encryption strength also depends on the optimum encryption strength your server offers or can achieve. The encryption strength heavily depends on your server configuration. If your server isn’t configured for 256-bit encryption, it’s entirely possible that you could be using encryption as low as 40 bits.

We’re not trying to scare you or anything, but we think it’s important to point out that you must configure your server to optimize your website security.

SSL Encryption Strength and the Time It Would Take to Crack It

You might have heard that nothing is unbreakable in the world of internet, and that’s true as well. SSL encryption strength being used today is breakable — but it would take an extremely long time to do so. How much exactly? Well, more than the age of the age of the universe. Yes, it’d take that long for today’s supercomputers to crack 128-bit encryption, the least strength of SSL/TLS encryption being used today.

Here’s how much time it’d take to crack SSL certificates of various encryption strengths:

Encryption Strength Time to Crack
   56 bit 399 Seconds
128 bit 1.02 x 1018 years
192 bit 1.872 x 1037 years
256 bit 3.31 x 1056 years

Which SSL Certificate Should I Choose?

As we saw, the higher the encryption strength, the lesser the chances of the key getting cracked. Therefore, we’d recommend installing an SSL certificate having 256-bit or higher symmetric encryption key length. You should also must make sure that your server is configured to support it.

Although the encryption level should be a major consideration in selecting an SSL certificate, there are other factors you shouldn’t overlook. These factors include:

  • Warranty amount
  • Encryption algorithm (RSA, ECC, etc.)
  • Validation level (DV, OV or EV)
  • Number of domains to be secured

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