Secure Sockets Layer (SSL) - Definition & Overview

What is SSL?

SSL (Secure Sockets Layer) is a widely used protocol that creates an encrypted connection between a website’s server and a user's browser to ensure secure data transfer. Originally developed by Netscape in the mid-1990s, SSL paved the way for safer online communication by preventing unauthorized access, tampering, or data leaks during transmission.

Although modern websites now use TLS (Transport Layer Security), the updated and more secure version of SSL, the term “SSL” is still widely used in digital security contexts. SSL plays a foundational role in enabling HTTPS, helping websites protect user information, login credentials, and payment details from cyber threats.

SSL certificates, issued by trusted Certificate Authorities (CAs), authenticate the identity of a website and enable encrypted sessions to prevent data tampering or eavesdropping during transmission.

How Does SSL/TLS Work?

SSL/TLS operates through a multi-step process that secures data during transmission between a client and a server. The process includes encryption, authentication, and data integrity checks.

1. Handshake Process
   The connection begins with an SSL/TLS handshake, during which the client and server exchange cryptographic keys and negotiate encryption algorithms. This step verifies the server’s identity using its digital certificate.
2. Session Key Generation
   Once authenticated, both parties generate a shared session key. This key is used to encrypt and decrypt the data transmitted during the session.
3. Data Encryption
   All information exchanged is encrypted, ensuring that it cannot be intercepted or read by unauthorized parties.
4. Data Integrity
   SSL/TLS uses message authentication codes (MACs) to confirm that the data has not been altered in transit.

These mechanisms work together to provide a secure and reliable communication channel across untrusted networks.

What is an SSL Certificate?

An SSL certificate is a digital credential that authenticates the identity of a website and enables encrypted connections using SSL/TLS protocols. It acts as a trusted indicator that the website is legitimate and that communication with it is secure.

The certificate contains the website's public key, which is used to initiate encrypted communication. When a user connects to the site, their browser uses this public key to establish a secure session. The server, in turn, uses a corresponding private key to decrypt the data. This process ensures confidentiality, authentication, and integrity of the information exchanged.

SSL certificates are issued by Certificate Authorities (CAs),  trusted entities responsible for verifying the identity of the certificate requester and signing the certificate to establish trust.

Types of SSL Certificates

SSL certificates vary based on domain coverage and validation level. Choosing the right type depends on the number of domains and the level of trust required.

Based on Domain Coverage:

• Single-Domain SSL Certificate
  Provides protection for one fully qualified domain name. It is best suited for websites with a single URL.
• Wildcard SSL Certificate
  Secures one domain and all its associated subdomains. Ideal for businesses managing multiple subdomains under the same root.
• Multi-Domain SSL Certificate
  Covers multiple unrelated domains with a single certificate. Useful for organizations managing diverse web properties.

Based on Validation Level:

• Domain Validation (DV)
  Offers basic validation by confirming domain ownership. It is quick to issue and commonly used for blogs or small websites.
• Organization Validation (OV)
  Requires verification of the organization’s identity in addition to domain ownership. It is more credible and suited for business websites.
• Extended Validation (EV)
  Requires a thorough verification process, including legal and operational checks. It is designed for entities that require the highest level of trust and visibility.

How to Add SSL to a Website

Implementing an SSL certificate is a key step in securing website traffic and enabling HTTPS. While the exact process may vary based on server environment or hosting provider, the core steps generally include the following:

1. Select a Certificate Authority (CA)
   Begin by choosing a trusted certificate authority, such as DigiCert, Sectigo, or Let’s Encrypt. These organizations validate your request and issue the SSL certificate.
2. Create a Certificate Signing Request (CSR)
   Generate a CSR through your hosting control panel or server interface. The CSR includes essential details such as your public key, domain name, and organization information.
3. Submit the CSR for Validation
   Upload the CSR to the chosen certificate authority. After verifying the information, the CA issues a digitally signed SSL certificate.
4. Install the SSL Certificate
   Once received, the certificate must be installed on the web server. This process may differ based on the hosting platform (e.g., Apache, NGINX, or cPanel environments).
5. Enable HTTPS Redirection
   After installation, configure the server or .htaccess file to redirect all HTTP traffic to HTTPS, ensuring secure access by default.

SSL providers support secure digital interactions by enabling data encryption, verifying website authenticity, and maintaining trust and data integrity.