What is a TLS Certificate?

If you’ve ever noticed a little padlock symbol next to a website’s URL in your browser, you’ve already become aware of the presence of a TLS certificate, even if you weren’t 100 percent sure what it meant. Behind that symbol lies an essential part of internet security, known as TLS, or Transport Layer Security.

Conversely, you may occasionally have encountered a warning that screams “Not Secure!” whenever you try to visit a site without a TLS certificate. This is your browser’s way of trying to protect you from potentially providing data to an insecure website.

This article will break down what a TLS certificate is, how it works, why TLS certificates are generally considered essential these days, and how they impact our daily online interactions.

What Is TLS?

Transport Layer Security (TLS) is a cryptographic protocol designed to secure data as it travels across networks. It’s essentially the technology that allows your browser and a website to communicate privately.

TLS was created as an update to SSL (Secure Sockets Layer), and though “SSL” is often used interchangeably with TLS, TLS is now the more accurate term.

A TLS certificate is a digital certificate that verifies the identity of a website and enables secure, encrypted connections.

TLS certificates are essentially the new SSL certificates. Websites have traditionally used SSL certificates, and now they’re being called TLS certificates, or TLS/SSL certificates, due to the fact that SSL has been deprecated in favor of TLS. Regardless of the name you use, they have the same purpose; to verify a website’s identity and to enable secure, encrypted connections.

When a website has a TLS/SSL certificate, it means that the data sent between your browser and the server is encrypted, preventing outsiders from intercepting sensitive information, like passwords and credit card numbers.

The certificate also provides proof that the site is who it claims to be, verified by a trusted authority.

When you see a site with “https://” instead of “http://” in the URL, it’s using TLS, and the certificate helps establish this secure connection.

Here, HTTP stands for HyperText Transfer Protocol, and HTTPS stands for HyperText Transfer Protocol Secure.

How Does a TLS Certificate Work?

TLS certificates use public-key cryptography to establish a secure connection. Here’s a simplified version of the process:

Handshake: When you visit a website, your browser and the website server perform a “handshake,” where they exchange information to establish a secure connection.
Key Exchange: The server presents its TLS certificate, which contains a public key, and your browser checks its authenticity.
Encryption: Once verified, the browser and server agree on an encryption key, and all further communication between them is encrypted.

This process happens instantly and behind the scenes, but it is crucial for ensuring online privacy and security.

Why Are TLS Certificates Important?

TLS certificates are essential for three primary reasons:

Data Security: They encrypt sensitive information, such as login credentials and payment details, which is crucial for online privacy and trust. When data is encrypted, any attacker that intercepts the packets of data being transferred would see nothing but an unreadable jumbled mess. And the stronger the encryption, the less likely the attacker will be able to decrypt it and see anything meaningful.
Authentication and Trust: They confirm the identity of websites, protecting users from phishing attacks and fraudulent sites. This confirmation of identity is done by a universally trusted third party, called a Certificate Authority (CA).
SEO and Browser Benefits: Search engines such as Google favor HTTPS (secure sites) for search rankings, and modern browsers will flag or warn users about insecure (HTTP-only) sites, which can harm a website’s reputation.

Types of TLS Certificates

Not all TLS certificates are created equal. Here’s a brief look at the main types:

Domain Validated (DV) Certificates: These confirm ownership of the domain but provide minimal verification. They’re ideal for smaller websites that don’t handle sensitive information.
Organization Validated (OV) Certificates: These involve more validation, verifying the domain and the organization’s identity. They’re suitable for medium-sized businesses.
Extended Validation (EV) Certificates: EV certificates require the most rigorous validation process, often involving legal documentation. They provide the highest level of trust and are widely used by e-commerce sites and large corporations.

How to Obtain a TLS Certificate

To get a TLS certificate, website owners have several options:

Trusted Certificate Authorities (CAs): Website owners can purchase a TLS certificate from trusted CAs like DigiCert, GlobalSign, or Comodo. These CAs offer certificates with varying levels of validation, from Domain Validated (DV) to Extended Validation (EV), depending on the security needs of the website.
Free CAs: Organizations like Let’s Encrypt provide free TLS certificates. This is a popular option for smaller websites and bloggers, as it enables them to secure their websites without additional cost. Some web hosts provide these free TLS certificates in their hosting plans. These are often implemented via the hosting control panel, such as Plesk, and they will typically include auto-renew functionality (so that you don’t need to manually renew it every time it’s about to expire).
Through a Content Delivery Network (CDN): Many CDN providers, such as Cloudflare, Fastly, and Akamai, offer TLS certificates as part of their services. When a website uses a CDN, the TLS certificate can be managed directly through the CDN, streamlining the setup and renewal process. CDNs can also enhance site performance by serving content from geographically closer servers while securing the connection.

It’s possible to install a TLS certificate on the web server, while also using a certificate with a CDN. The one on the web server can be used to encrypt data transferred between the origin server and the CDN, and the CDN certificate is used to encrypt data between the CDN and the end user.

The Role of TLS in Everyday Web Security

The web depends on TLS for a wide range of activities, from shopping online to checking your bank balance. TLS secures everything from login credentials to bank transactions, helping build a safer internet where people can interact without risking their personal information.

There was a time where SSL (TLS’s precursor) was reserved only for pages where sensitive data was being transferred between the client and the server. This meant that most website URLs started with http:// (instead of https://). But in recent years, HTTPS has become the default protocol, and many websites implement code that automatically redirects any http:// traffic to its https:// equivalent.

Despite the apparent difference between these two protocols, HTTPS is actually just an implementation of TLS/SSL encryption on top of the HTTP protocol.

The Future of TLS and Web Security

As cyber threats continue to evolve, TLS is also advancing to ensure greater levels of security. The internet has already shifted toward HTTPS as a standard, and it’s almost a certainty that security standards will need to evolve as more threats emerge.

The Internet Engineering Task Force (IETF) is responsible for producing the public specifications for Transport Layer Security (TLS). The TLS specification is maintained and developed by the IETF TLS Working Group.