How does a Single SSL Certificate Secure Multiple Domains?

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Cyber threats are always raising the graph line with enhanced data breaches, intrusions, phishing attacks, SQL injection attacks, malware exploits, etc. The cost of security breaches (USD 4.45 million – IBM DBR Report) is extremely high, thus making companies bankrupt at times and hence the security of digital data is becoming extremely vital for small as well as large industries. 

One such security solution is to install an SSL (Secure Socket Layers) certificate on the website.

Let’s get started.

About SSL Certificates

SSL security certificates encrypt all client-server exchanges by converting the plain data into a cipher and non-readable form. Only the intended recipient will be able to decipher (decrypt) the data using a special key. 

Different SSL certificates secure domains and sub-domains depending on the type of SSL certificate installed on the site. Securing a single domain by purchasing a single SSL certificate is easy, but web owners who own varied businesses and have large companies always wonder how to secure their multiple businesses (sites). How many SSL certificates need to be purchased if multiple domains need to be secured?  

This blog is all about Multi-domain SSL certificates and the securities they offer.

Is it possible to have a Single SSL certificate for Securing Multiple Domains?

The answer to the above question will amaze you since a single SSL certificate is sufficient to secure all your domains (all businesses).

Yes! Yes! Yes! You heard it right. Only one single Multi-domain SSL certificate can secure all your site domains and all the site sub-domains of varied levels.

One multi-domain SSL certificate can save you time and money since you are liberated from buying multiple certificates from multiple vendors.

Types of Multi-Domain SSL Certificates

Three types of muti-domain SSL certificates can secure the web. A briefing on each of them will help you choose your digital security in a better way.

1. Multi-Domain SSL Certificate:

A multi-domain SSL certificate or a SAN (Subject Alternate Name) SSL certificate permits users to add varied hostnames (URLs and Domain names) in a single certificate. When a user accesses a site having this certificate, their browser will verify the URL of the website with the one stated in the SAN field of the SSL certificate. If both the URLs match, a secured connection is established.

An SSL certificate for multiple domains can secure up to 250 domains and sub-domains depending on the Certificate Authority (CA) issuing the same. This budget-friendly and hassle-free certificate is easily manageable and secures your whole web with a single certificate.

Example: GeoTrust Multi-domain EV SSL, Comodo PositiveSSL Multi-domain, etc. cheap Multi-domain SSL certificates are available at $15 that secure your whole web at a cost-effective rate.

2. Multi-Domain Wildcard SSL:

Multi-Domain Wildcard SSL is used to secure multiple wildcard domains, as the name suggested. If you are someone who wants to secure multiple wildcard domains under one certificate, you should not look further. There are many certificate authorities that offer this certificate, such as Comodo and Sectigo. 

The best thing about Multi-Domain Wildcard certificates is that they can secure FQDN and wildcard domains under their SAN entries. There are many reasons to consider a Multi-Domain Wildcard SSL certificate, and they are as follows:

  • It secures unlimited subdomains under multiple domains
  • You can easily manage this certificate as there’s no science behind it. 
  • You can protect all domains with a single certificate 
  • It is available in DV and OV
  • Ideal for businesses seeking to protect their sites and all subdomains

Example: Comodo Multi-Domain Wildcard SSL, Sectigo Multi-Domain Wildcard SSL

3. Unified Communication Certificates:

A Unified Communication Certificate (UCC) is also termed a Microsoft Exchange SSL certificate. The name itself states that these certificates are specifically used for Microsoft Exchange servers and office communication servers. 

When a UCC is installed on a Microsoft Exchange or Office Communications server, it comprises each website name that is being hosted on that IP address stated in the SAN field. So, if a user wants to access a site that is hosted on that IP address, the device will display a certificate with the desired domain name to match it and to prevent SSL error display.

These certificates are also used for securing varied websites, FQDNs (Fully Qualified Domain Names), and web pages. 

Depending on the CA who issues the UCC certificate, the web owner can secure up to 250 domains. The use of this certificate helps save time, money, and other resources.

Examples: Comodo UCC (OV), Comodo (DV) UCC, etc.

How Encryption Works for Multi-Domain Certificates?

Though multiple types of SSL certificates offer multiple securities to your website, the level of encryption that each SSL certificate provides is the same, i.e., they all provide 256-bit encryption security. 

The only factor which needs to be considered is the reliability of the SSL certificate provider. It’s advisable to always check the SSL certificate provider’s reviews and reputation before purchasing SSL certificates. Approach a trustworthy CA for purchasing this digital security solution to ensure site security and credibility.

About SSL Encryption

SSL encryption process is based on public key cryptography wherein two keys are used. The public key encrypts the data and the private key decrypts the same.  

When a user (browser) visits a website (server) having a Multi-domain SSL certificate, they carry out the SSL handshake process. This SSL handshake process ensures the task of encryption and decryption of the data sent by the user. It encrypts the data so that it becomes non-readable till it reaches its destination (intended recipient). 

During this process, the browser will confirm the validity of the Multi-domain SSL certificate installed on the site and positive confirmation will establish a secure connection. The same will be established using the client’s public key and the server’s private key. Both these keys together create a session key, which helps in securing the connection between both parties. 

The SSL handshake process thus ensures customer data privacy and site security.

Wrapping Up

Installing a multi-domain SSL certificate, a wildcard SSL or a UCC depends on your business needs and the domains and sub-domains that need to be safeguarded. 

If there is a root domain and multiple subdomains (more sub-domains may be added in the future) that need security, purchasing a wildcard SSL certificate is the best option, but in case there are multiple domains that need to be secured, then purchasing a multi-domain SSL certificate is the best choice. 

One disadvantage of using a multi-domain SSL certificate is that it is a bit pricey compared to other SSL certificates. But, if we look at the security level that it offers, it’s worth the price. Another drawback of using this certificate is the huge key exposure. The private key and the public key are extensively used and this can lower the security shield. Many exploits like brute-force attacks and MIM (man-in-middle) attacks can be successfully carried out if any of the keys are compromised. 

But, its enhanced security, streamlined certificate management tasks, costs, benefits, etc. far surpass the cons, and hence large enterprises and corporate owners love to use a single multi-domain SSL certificate for securing their entire digital empire.

That’s it.

We hope this article helped you to learn about Single SSL Certificate Secure Multiple Domains Tutorial Example in a very detailed way.

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Sanjay KumarHello friends, I am Sanjay Kumar a Web Developer by profession. Additionally I'm also a Blogger, Youtuber by Passion. I founded Online Web Tutor and Skillshike platforms. By using these platforms I am sharing the valuable knowledge of Programming, Tips and Tricks, Programming Standards and more what I have with you all. Read more