What is an SSL certificate — Definition and Explanation

What is an SSL certificate?

An SSL certificate is a digital certificate that authenticates a website's identity and enables an encrypted connection. SSL stands for Secure Sockets Layer, a security protocol that creates an encrypted link between a web server and a web browser.

Companies and organizations need to add SSL certificates to their websites to secure online transactions and keep customer information private and secure.

In short: SSL keeps internet connections secure and prevents criminals from reading or modifying information transferred between two systems. When you see a padlock icon next to the URL in the address bar, that means SSL protects the website you are visiting.

Since its inception about 25 years ago, there have been several versions of SSL protocol, all of which at some point ran into security troubles. A revamped and renamed version followed — TLS (Transport Layer Security), which is still in use today. However, the initials SSL stuck, so the new version of the protocol is still usually called by the old name.

Photo by Samuel Spagl on Unsplash

How do SSL certificates work?

SSL works by ensuring that any data transferred between users and websites, or between two systems, remains impossible to read. It uses encryption algorithms to scramble data in transit, which prevents hackers from reading it as it is sent over the connection. This data includes potentially sensitive information such as names, addresses, credit card numbers, or other financial details.

The process works like this:

  1. A browser or server attempts to connect to a website (i.e., a web server) secured with SSL.
  2. The browser of the server requests that the web server identify itself.
  3. The web server sends the browser or server a copy of its SSL certificate in the response.
  4. The browser or server checks to see whether it trusts the SSL certificate. If it does, it signals this to the webserver.
  5. The web server then returns a digitally signed acknowledgment to start an SSL encrypted session.
  6. Encrypted data is shared between the browser or server and the webserver.

This process is sometimes referred to as an “SSL handshake.” While it sounds like a lengthy process, it takes place in milliseconds.

When a website is secured by an SSL certificate, the acronym HTTPS (which stands for HyperText Transfer Protocol Secure) appears in the URL. Without an SSL certificate, only the letters HTTP — i.e., without the S for Secure — will appear. A padlock icon will also display in the URL address bar. This signals trust and provides reassurance to those visiting the website.

To view an SSL certificate’s details, you can click on the padlock symbol located within the browser bar. Details typically included within SSL certificates include:

  • The domain name that the certificate was issued for
  • Which person, organization, or device it was issued to
  • Which Certificate Authority issued it
  • The Certificate Authority’s digital signature
  • Associated subdomains
  • Issue date of the certificate
  • The expiry date of the certificate
  • The public key (the private key is not revealed)
Photo by Markus Spiske on Unsplash

Why do you need an SSL certificate?

Websites need SSL certificates to keep user data secure, verify ownership of the website, prevent attackers from creating a fake version of the site, and convey trust to users.

If a website is asking users to sign in, enter personal details such as their credit card numbers, or view confidential information such as health benefits or financial information, then it is essential to keep the data confidential. SSL certificates help keep online interactions private and assure users that the website is authentic and safe to share private information with.

More relevant to businesses is the fact that an SSL certificate is required for an HTTPS web address. HTTPS is the secure form of HTTP, which means that HTTPS websites have their traffic encrypted by SSL. Most browsers tag HTTP sites — those without SSL certificates — as “not secure.” This sends a clear signal to users that the site may not be trustworthy — incentivizing businesses who have not done so to migrate to HTTPS.

An SSL certificate helps to secure information such as:

  • Login credentials
  • Credit card transactions or bank account information
  • Personally identifiable information — such as full name, address, date of birth, or telephone number
  • Legal documents and contracts
  • Medical records
  • Proprietary information
Photo by Carlos Muza on Unsplash

Types of SSL certificate

There are different types of SSL certificates with different validation levels. The six main types are:

  1. Extended Validation certificates (EV SSL)
  2. Organization Validated certificates (OV SSL)
  3. Domain Validated certificates (DV SSL)
  4. Wildcard SSL certificates
  5. Multi-Domain SSL certificates (MDC)
  6. Unified Communications Certificates (UCC)

Extended Validation certificates (EV SSL)

This is the highest-ranking and most expensive type of SSL certificate. It tends to be used for high-profile websites which collect data and involve online payments. When installed, this SSL certificate displays the padlock, HTTPS, name of the business, and the country on the browser address bar. Displaying the website owner’s information in the address bar helps distinguish the site from malicious sites. To set up an EV SSL certificate, the website owner must go through a standardized identity verification process to confirm they are authorized legally to the exclusive rights to the domain.

Organization Validated certificates (OV SSL)

This version of the SSL certificate has a similar assurance similar level to the EV SSL certificate since to obtain one; the website owner needs to complete a substantial validation process. This type of certificate also displays the website owner’s information in the address bar to distinguish it from malicious sites. OV SSL certificates tend to be the second most expensive (after EV SSLs), and their primary purpose is to encrypt the user’s sensitive information during transactions. Commercial or public-facing websites must install an OV SSL certificate to ensure that any customer information shared remains confidential.

Domain Validated certificates (DV SSL)

The validation process to obtain this SSL certificate type is minimal, and as a result, Domain Validation SSL certificates provide lower assurance and minimal encryption. They tend to be used for blogs or informational websites — i.e., which do not involve data collection or online payments. This SSL certificate type is one of the least expensive and quickest to obtain. The validation process only requires website owners to prove domain ownership by responding to an email or phone call. The browser address bar only displays HTTPS and a padlock with no business name displayed.

Wildcard SSL certificates

Wildcard SSL certificates allow you to secure a base domain and unlimited sub-domains on a single certificate. If you have multiple sub-domains to secure, then a Wildcard SSL certificate purchase is much less expensive than buying individual SSL certificates for each of them. Wildcard SSL certificates have an asterisk * as part of the common name, where the asterisk represents any valid sub-domains that have the same base domain. For example, a single Wildcard certificate for *website can be used to secure:

  • payments.yourdomain.com
  • login.yourdomain.com
  • mail.yourdomain.com
  • download.yourdomain.com
  • anything.yourdomain.com

Multi-Domain SSL Certificate (MDC)

A Multi-Domain certificate can be used to secure many domains and/or sub-domain names. This includes the combination of unique domains and sub-domains with different TLDs (Top-Level Domains) except for local/internal ones.

For example:

  • www.example.com
  • example.org
  • mail.this-domain.net
  • example.anything.com.au
  • checkout.example.com
  • secure.example.org

Multi-Domain certificates do not support sub-domains by default. If you need to secure both www.example.com and example.com with one Multi-Domain certificate, then both hostnames should be specified when obtaining the certificate.

Photo by Kelly Sikkema on Unsplash

Unified Communications Certificate (UCC)

Unified Communications Certificates (UCC) are also considered Multi-Domain SSL certificates. UCCs were initially designed to secure Microsoft Exchange and Live Communications servers. Today, any website owner can use these certificates to allow multiple domain names to be secured on a single certificate. UCC Certificates are organizationally validated and display a padlock on a browser. UCCs can be used as EV SSL certificates to give website visitors the highest assurance through the green address bar.

It is essential to be familiar with the different types of SSL certificates to obtain the right type of certificate for your website.

How to obtain an SSL certificate

SSL certificates can be obtained directly from a Certificate Authority (CA). Certificate Authorities — sometimes also referred to as Certification Authorities — issue millions of SSL certificates each year. They play a critical role in how the internet operates and how transparent, trusted interactions can occur online.

The cost of an SSL certificate can range from free to hundreds of dollars, depending on the level of security you require. Once you decide on the type of certificate you require, you can then look for Certificate Issuers, which offer SSLs at the level you require.

Photo by Markus Spiske on Unsplash

Obtaining your SSL involves the following steps:

  • Prepare by getting your server set up and ensuring your WHOIS record is updated and matches what you are submitting to the Certificate Authority (it needs to show the correct company name and address, etc.)
  • Generating a Certificate Signing Request (CSR) on your server. This is an action your hosting company can assist with.
  • Submitting this to the Certificate Authority to validate your domain and company details
  • Installing the certificate they provide once the process is complete.

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