HTTPS / SSL: Complete Definition and Guide

What is HTTPS / SSL?

HTTPS, standing for HyperText Transfer Protocol Secure, is the standard protocol that secures communications between a web browser and a server. It is the classic HTTP protocol encapsulated in an SSL/TLS (Secure Sockets Layer / Transport Layer Security) encryption layer that guarantees three fundamental properties: confidentiality (data cannot be read by third parties), integrity (data cannot be modified in transit), and authenticity (the server is genuinely who it claims to be).

To be precise, SSL is the now-obsolete predecessor of the security protocol — the last version, SSL 3.0, dates from 1996 and has known vulnerabilities. TLS (Transport Layer Security) is its modern successor, the current version being TLS 1.3 (2018). By convention, people often still refer to "SSL" when they are actually using TLS. "SSL certificates" are in fact TLS certificates, and modern HTTPS connections exclusively use TLS.

The switch to HTTPS has become mandatory for any serious website. Modern browsers now mark HTTP sites as "Not Secure" in the address bar, Google uses HTTPS as an SEO ranking signal, and many modern web APIs (geolocation, notifications, Service Workers) only work in a secure HTTPS context.

Why HTTPS / SSL Matters

HTTPS is no longer a luxury reserved for e-commerce or banking sites. It is an absolute necessity for any website, even a simple blog or brochure page. The reasons are multiple and convergent.

• User data protection: without HTTPS, any data submitted via a form (credentials, personal data, messages) travels in clear text over the network and can be intercepted by any network intermediary. This is particularly critical on public Wi-Fi networks.
• Visitor trust: the green padlock in the address bar has become a universal trust indicator. Its absence (marked by a "Not Secure" warning) drives visitors away and damages your brand credibility.
• Positive SEO impact: since 2014, Google has integrated HTTPS as a ranking signal. HTTPS sites benefit from an advantage in search results compared to their HTTP equivalents.
• GDPR compliance: the General Data Protection Regulation requires appropriate technical measures to protect personal data. HTTPS encryption is considered an essential baseline measure.
• Modern web features: HTTP/2, Service Workers, Progressive Web Apps, geolocation, and many recent JavaScript APIs require an HTTPS context to function.

How It Works

When a browser connects to an HTTPS site, a process called the "TLS handshake" begins before any data exchange. This process takes fractions of a second and establishes the connection's security parameters.

The browser contacts the server and announces the TLS versions and cryptographic suites it supports. The server responds by choosing the best common combination and sends its TLS certificate. This certificate contains the server's public key and is signed by a recognised Certificate Authority (CA), which proves the server's identity.

The browser verifies the certificate's chain of trust: is it signed by a trusted CA? Has it not expired? Does the domain name match? If everything is valid, the browser and server proceed with a key exchange using asymmetric cryptography to generate a shared symmetric session key. All subsequent communication is encrypted with this symmetric key, which is much faster than asymmetric cryptography.

With TLS 1.3, the handshake has been optimised to complete in a single round trip (1-RTT) instead of two, and even supports 0-RTT mode for returning connections, considerably reducing latency compared to previous versions.

Concrete Example

At KERN-IT, HTTPS is a non-negotiable prerequisite for every deployment. All our production Django applications use Let's Encrypt certificates, a free and automated certificate authority that has democratised access to HTTPS. Our Nginx configuration systematically includes automatic HTTP to HTTPS redirection, HTTP/2 protocol activation for better performance, and configuration of complementary security headers (HSTS, X-Frame-Options, Content-Security-Policy).

Certificate renewal is automated via Certbot and a cron job: Let's Encrypt certificates have a 90-day lifespan, and Certbot automatically renews them 30 days before expiration. This automation eliminates the risk of forgotten renewal, which is one of the most frequent causes of HTTPS outages in production.

Implementation

1. Install Certbot: on Ubuntu, install the certbot package and the nginx plugin (apt install certbot python3-certbot-nginx).
2. Obtain the certificate: run certbot --nginx -d your-domain.be to automatically obtain and configure the SSL certificate. Certbot modifies the Nginx configuration to enable HTTPS.
3. Force HTTPS redirection: configure Nginx to redirect all HTTP requests (port 80) to HTTPS (port 443) with a permanent 301 code.
4. Enable HTTP/2: add the http2 parameter in the listen 443 ssl http2 directive to benefit from multiplexing and header compression.
5. Configure HSTS: add the Strict-Transport-Security header to instruct browsers to always use HTTPS for your domain, even if the user types "http://".
6. Automate renewal: verify that Certbot's systemd timer is active (systemctl status certbot.timer) for automatic certificate renewal.
7. Verify configuration: use tools like SSL Labs (ssllabs.com) to audit your TLS configuration and obtain an A+ grade confirming best practices.

Associated Technologies and Tools

• Let's Encrypt: free, automated, and open certificate authority.
• Certbot: ACME client for automatically obtaining and renewing Let's Encrypt certificates.
• Nginx: handles SSL/TLS termination and HTTP to HTTPS redirection.
• HSTS: security mechanism forcing browsers to use HTTPS.
• HTTP/2: modern transfer protocol that requires HTTPS and significantly improves performance.
• SSL Labs: free tool for auditing and grading a site's TLS configuration.

Conclusion

HTTPS is no longer optional — it is a baseline standard that every website must implement. Thanks to Let's Encrypt, the financial cost has disappeared, and thanks to Certbot, the technical complexity is reduced to a minimum. At KERN-IT, HTTPS is an integral part of every Nginx deployment we configure for our Belgian clients. Beyond security, it is an investment in SEO, user trust, GDPR compliance, and access to modern web features. Ensure your site uses not only HTTPS but also an optimal TLS configuration with appropriate security headers.