What is a Secure Sockets Layer (SSL) certificate?

March 08, 2025 • By KWD

An SSL certificate is metadata containing a website's public key and identity information, enabling HTTPS encryption to secure internet traffic and authenticate server identity.

Key Takeaways

SSL certificates enable websites to use HTTPS, encrypting data in transit and protecting user information from interception.
SSL certificates contain domain name, issuer details, expiration date, public key, and digital signature from a certificate authority.
Public and private key pairs work together to encrypt and decrypt data; only the private key decrypts data encrypted with the public key.
Browsers flag HTTP sites as not secure, encouraging migration to HTTPS and increasing user trust in websites.
Free SSL certificates are available from providers like LetsEncrypt and Cloudflare, reducing barriers to implementing website security.

SSL certificates enable websites to transition from HTTP to HTTPS, which is a more secure protocol. An SSL certificate is metadata maintained on the website's origin server. SSL certificates enable SSL/TLS encryption and contain the website's public key and identification, as well as other information. This file contains the origin server's public key and identity verification information. The private key is maintained in a secure and confidential manner as well.

What exactly is SSL?

SSL stands for Secure Sockets Layer, more generally referred to as Transport Layer Security (TLS), is a protocol used to encrypt Internet traffic and authenticate the identity of servers. SSL certificate is utilized by any website with an HTTPS URL.

What information is contained in an SSL certificate?

SSL certificates contain the following:

Domain name for which the certificate was issued
Which individual, organization, or device received it
Which issuing body issued it?
The digital signature of the certificate authority
Subdomains that are associated
The certificate's issue date
Certificate expiration date
The public encryption key (the private key is kept secret)

SSL's public and private keys are essentially lengthy strings of characters that are used to encrypt and decrypt data. Only the private key is capable of decrypting data encrypted using the public key, and vice versa.

Why is an SSL certificate required for websites?

An SSL certificate is required for a website in order to protect user data, validate the website's ownership, prevent attackers from building a false version of the site, and earn user confidence.

SSL/TLS encryption is possible because SSL certificates enable the pairing of public and private keys. Clients (such as web browsers) obtain the public key required to establish a TLS connection from the SSL certificate of the server.

SSL certificates authenticate that a client is communicating with the correct server that truly owns the domain. This contributes to the prevention of domain spoofing and other types of attacks.

HTTPS: Most importantly for businesses, an HTTPS web address requires an SSL certificate. HTTPS protocol is the secure version of HTTP protocol and are used to encrypt the up and down traffic.

Along with safeguarding user data in transit, HTTPS increases the trustworthiness of websites from the user's perspective. While many users will not notice the difference between a http:// and https:// web address, most browsers have begun to flag HTTP sites as "not secure" in more obvious ways, in an attempt to encourage users to migrate to HTTPS and increase security.

How can a website receive a secure socket layer (SSL) certificate?

To obtain a valid SSL certificate, domains must contact a certificate authority (CA). A CA is a third-party company that issues and distributes SSL certificates. Additionally, the CA will digitally sign the certificate using their own private key, allowing it to be verified by client devices. The majority of CAs, but not all, charge a fee for granting an SSL certificate.

Once the certificate has been issued, it must be deployed and activated on the origin server of the website. Typically, web hosting firms can take care of this for website operators. Once activated on the origin server, the website will be able to load over HTTPS, encrypting and securing all traffic to and from the website.

What is an SSL certificate that is self-signed?

Anyone can create their own SSL certificate by creating a public-private key pair with all required information. These certificates are referred to as self-signed certificates since the digital signature used is the website's own private key, rather than one from a CA.

However, with self-signed certificates, no external authority can verify that the origin server is indeed who it claims to be. Browsers may not trust self-signed certificates and may continue to label sites that use them as "not secure," despite the https:// URL. Additionally, they may disconnect the connection entirely, preventing the website from loading.

Can we get an SSL certificate for free?

There are numerous certificate authorities which provide SSL certificates for free. Some of them are LetsEncrypt, Cloudflare SSL, SSLforFree, ZeroSSL etc. If you are a cPanel user, you can generate free SSL certificates if the before mentioned SSL providers are integrated into cPanel.

Why some SSL certificates are given for free?

Most of the free SSL certificate providers indicate that they want to create a privacy based Internet which is safe, transparent and, secure.

Frequently Asked Questions

SSL stands for Secure Sockets Layer, now called Transport Layer Security (TLS). It is a protocol that encrypts internet traffic and authenticates the identity of servers.

Contact a certificate authority (CA), a third-party company that issues SSL certificates. Many CAs charge a fee, but some provide free certificates. Once issued, the certificate must be deployed on your origin server, typically with help from your web hosting provider.

An SSL certificate contains the domain name, recipient organization or device, issuing authority, digital signature, associated subdomains, issue and expiration dates, and the public encryption key.

SSL certificates protect user data, validate website ownership, prevent attackers from creating fake versions of your site, and increase user trust. They enable HTTPS, which browsers now display as more secure than HTTP.

A self-signed certificate is one created by the website owner using their own private key instead of a certificate authority. Browsers may not trust them and may label sites as not secure or refuse to load them entirely.