How SSL Certificates Work—and Why They Still Matter

What Is an SSL Certificate?

An Secure Sockets Layer (SSL) certificate—now technically a TLS certificate—is a digital certificate that verifies a domain’s identity and enables HTTPS encryption between a server and a user’s browser.

Once installed, it:

• Enables HTTPS and displays a padlock in the browser
• Verifies domain validation through a Certificate Authority (CA)
• Facilitates secure communication using TLS protocols

Note that although the term “SSL” persists, SSL protocols have been fully replaced by TLS—Transport Layer Security—which is more secure and efficient.

In a digital environment where trust is often established in milliseconds, SSL certificates can help garner user confidence and protect sensitive data from interception.

How SSL Certificates Work

Behind every padlock icon in a browser is a complex handshake process that verifies identity and initiates encrypted communication, essentially securing your information from prying eyes online. Here’s how SSL certificates work to establish secure, trusted connections:

Certificate Issuance:

• A trusted Certificate Authority (CA) validates your identity
• A certificate contains:
  • The domain name
  • A public key
  • CA signature
  • SSL expiration date

TLS Handshake:

• The browser initiates a TLS handshake
• The server shares its SSL certificate and cipher suite
• Exchange and verify certificates
• Use asymmetric encryption to generate a shared key

Secure Session Established:

• HTTPS activates in the browser
• Traffic is encrypted and authenticated in transit

Why SSL Still Matters in 2025

Even with Zero Trust and modern encryption frameworks, HTTPS encryption and TLS certificates are essential for:

• Securing web applications
• Authenticating APIs and cloud workloads
• Enabling email encryption
• Establishing brand trust and facilitating Search Engine Optimization (SEO)

As regulations evolve and threat actors continue to look for the weakest link, SSL/TSL is not just a technical detail. It should be a board-level concern.

Risks of Poor Certificate Hygiene

1. Expired Certificates:

• Trigger browser security warnings
• Cause browser warnings and API failures
• Harm user trust and search rankings

2. Insecure Validation:

• Domain validated certs used for phishing
• Weak validation allows impersonation

3. Chain Misconfigurations:

• Missing intermediate certs can break trust
• Incomplete chains can cause page load errors

4. Lack of Monitoring:

• Shadow IT and fragmented ownership expands attack surface unnecessarily
• Forgotten certs lead to unmonitored expiration dates and compliance or downtime issues

SSL and Compliance

Properly using SSL/TLS can help meet numerous compliance requirements, such as:

• PCI-DSS 4.0, a standard for protecting payment card data, lists numerous requirements related to SSL/TLS security
• HIPAA, a standard for healthcare entities, doesn’t explicitly mandate encryption, but it is an “addressable” requirement, meaning it should be completed if it is reasonable
• GDPR, for data protection the European Union, encourages HTTPS for protecting user data

Final Takeaway

Understanding how SSL certificates work is foundational to gaining trust on the web. Whether securing public applications or private infrastructure, managing digital certificates, TLS handshakes, and certificate transparency are vital to compliance, uptime, and risk reduction.

SecurityScorecard monitors vendor-side certificate hygiene through SCDR. This includes detection of expired certificates, misconfigurations, and potential TLS issues—enabling earlier intervention before issues can escalate and malicious actors take advantage.

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