SSL Certificates Explained – HTTPS, TLS and Website Security | meine-ip.info

What Is an SSL Certificate?

When you visit a website starting with https:// (and see a padlock in your browser), an SSL/TLS certificate is at work. It enables two critical security functions:

Encryption – all data between your browser and the server is scrambled, unreadable to anyone intercepting it
Authentication – it proves the website is genuinely operated by who they claim to be

Despite the common name "SSL certificate," modern connections actually use TLS (Transport Layer Security), the successor to the deprecated SSL protocol. The term "SSL" is still widely used out of habit.

How HTTPS Works

When your browser connects to an HTTPS site, a TLS handshake takes place:

Your browser says hello and lists supported cipher suites
The server responds with its certificate and chosen cipher
Your browser verifies the certificate against trusted Certificate Authorities (CAs)
A session key is exchanged using asymmetric cryptography
All subsequent communication is encrypted with the session key

This entire process takes milliseconds.

What Does a Certificate Contain?

An SSL certificate is a digital document containing:

Field	Description
Subject	The domain name(s) the cert is valid for
Issuer	The Certificate Authority that signed it
Valid from / to	Validity period (typically 1 year)
Public key	Used for key exchange during TLS handshake
Serial number	Unique identifier
SAN (Subject Alternative Names)	Additional domains covered (wildcards: `*.example.com`)
Signature algorithm	e.g., SHA-256 with RSA

Types of SSL Certificates

By Validation Level

Type	Validation	Use Case
DV (Domain Validated)	Automated, proves domain ownership	Blogs, small sites
OV (Organization Validated)	Manual, verifies company identity	Business websites
EV (Extended Validation)	Rigorous, company shown in browser	Banks, e-commerce

By Coverage

Single domain – covers only example.com
Wildcard – covers *.example.com (all subdomains)
Multi-domain (SAN) – covers multiple unrelated domains

Free SSL Certificates

Let's Encrypt is a free, automated, open Certificate Authority that has made HTTPS universal. It's used by millions of websites and offers 90-day certificates that auto-renew.

Most web hosts now offer free Let's Encrypt certificates out of the box.

Certificate Chain of Trust

No certificate stands alone. The trust model works as follows:

Root CA (trusted by browsers)
  └── Intermediate CA
        └── Your website's certificate

Browsers come pre-installed with a list of trusted Root CAs (like DigiCert, GlobalSign, Let's Encrypt's root). They trust certificates signed by these authorities or their intermediates.

What Happens When a Certificate Expires?

If a certificate expires, browsers show a security warning blocking access to the site. Visitors see:

⚠️ Your connection is not private

This is why auto-renewal (as offered by Let's Encrypt / Certbot) is critical for production websites.

Checking a Certificate

You can inspect any website's SSL certificate:

In browser: Click the padlock → "Certificate" → view details
With our tool: Use our SSL Check Tool to see validity, issuer, expiry date, cipher strength and the full certificate chain

What to look for:

✅ Certificate is not expired
✅ Domain name matches exactly
✅ Issued by a trusted CA
✅ Strong key (RSA 2048+ or ECDSA 256+)
✅ Modern signature algorithm (SHA-256 or better)

HTTP vs HTTPS

	HTTP	HTTPS
Encryption	None	TLS encryption
Data integrity	Unprotected	Tamper-proof
Authentication	None	Verified identity
SEO	Penalized by Google	Preferred
Browser indicator	"Not secure"	Padlock

Since 2014, Google uses HTTPS as a ranking signal. In 2018, Chrome started marking all HTTP pages as "Not Secure." Today, there is no good reason to run a public website without HTTPS.

Last updated: April 2024