HTTPS Certificate Validation: Overview

When you visit a secure website (HTTPS), your browser needs to verify that the website’s security certificate is legitimate and hasn’t been compromised. This is like checking if an ID card is still valid and hasn’t been reported stolen.

There are three main methods websites use to prove their certificates are trustworthy:

1. Certificate Revocation List (CRL) Think of this like downloading a massive phone book of all “bad” certificates. It’s thorough but slow.
2. Online Certificate Status Protocol (OCSP) This is like calling the certificate authority directly to ask “Is this specific certificate still good?” It’s current but creates privacy concerns.
3. OCSP Stapling The smartest approach – the website gets a “certificate is valid” stamp ahead of time and shows it to you immediately. It’s fast, private, and reliable.

Why This Matters

• Faster Website Loading: Better certificate validation means websites load faster.
• Better Privacy: Advanced methods prevent certificate authorities from tracking which websites you visit.
• More Reliable Browsing: Modern methods work even when certificate authority servers have problems.

The Bottom Line OCSP Stapling is the modern, best-practice approach that provides the optimal balance of speed, privacy, and security. Most major websites are moving toward this method.

For website owners: Enable OCSP Stapling on your servers. Test your current setup at ssllabs.com.

For users: Modern browsers handle all this automatically – you just get faster, more secure browsing.

Let’s encrypt stopped support for OCSP. If you want to implement OCSP I recommend using zeroSSL.

Certificate Revocation List (CRL) – The Traditional Approach
What is CRL?

Certificate Revocation List (CRL) is the oldest method for checking if a security certificate is still valid. Think of it as a massive directory that lists all the certificates that have been marked as “bad” or compromised.

How CRL Works

1. Your browser connects to the website
2. The website sends its security certificate
3. Your browser downloads a complete list of all invalid certificates
4. Your browser checks if the website’s certificate is on this “bad” list
5. If not on the bad list, a secure connection is established

Advantages

✓ Simple and straightforward
✓ Works offline once downloaded
✓ Privacy friendly – no tracking

Disadvantages

✗ Very slow – large files to download
✗ Outdated – only updated daily
✗ Bandwidth heavy – downloads massive lists
✗ Inefficient – downloads millions of certificates to check one

The Bottom Line

CRL was an important stepping stone in internet security, but it’s like using a physical phone book in the smartphone age – it works, but there are much better alternatives available today.

Online Certificate Status Protocol (OCSP) – The Real-Time Approach

What is OCSP?

Online Certificate Status Protocol (OCSP) is like having a direct phone line to the certificate authority. Instead of downloading a huge list of bad certificates, your browser simply asks: “Is this specific certificate still valid right now?”

How OCSP Works

1. Your browser connects to the website
2. The website sends its security certificate
3. Your browser contacts the certificate authority and asks: “Is certificate #12345 still good?”
4. The authority responds with “Yes, it’s valid” or “No, it’s been revoked”
5. If valid, a secure connection is established

Think of it like calling a bank to verify if a specific credit card is still active.

Advantages of OCSP

• Real-Time Information: You get the most current status of any certificate.
• Efficient Data Transfer: Only small requests and responses are sent.
• Faster Than CRL: Much smaller data transfers than downloading entire lists.

Disadvantages of OCSP

• Privacy Problems: The certificate authority learns exactly which websites you visit and when.
• Browsing Tracking: Certificate authorities can build detailed profiles of your internet activity.
• Connection Dependency: Requires an additional internet connection that can fail.
• Single Point of Failure: If the authority’s server is down, certificate checking fails.
• Slows Down Browsing: Each website visit requires an extra network request.

The Privacy Concern

Imagine if every time you visited a website, you had to call a central authority and tell them “I’m visiting Amazon.com right now.” That’s essentially what OCSP does – it creates a detailed log of your browsing activity.

The Bottom Line

OCSP represents a significant improvement over CRL in terms of speed and accuracy, but its privacy implications and dependency on external servers make it less than ideal for modern internet users who value both security and privacy.

Most websites are now moving to OCSP Stapling, which provides the benefits of OCSP without the privacy and reliability drawbacks.

OCSP Stapling – The Smart Modern Solution

What is OCSP Stapling?

OCSP Stapling is like having a website get a “certificate of good health” stamp ahead of time and showing it to you immediately when you visit. The website does all the checking work in advance, so you get instant verification without any extra delays or privacy concerns.

How OCSP Stapling Works

Behind the Scenes:

1. The website server regularly asks the certificate authority: “Is my certificate still valid?”
2. The authority gives the server a signed proof saying “Yes, valid until [date]”
3. The server keeps this proof ready for visitors

When You Visit

• You connect directly to the website
• The server immediately sends both its certificate AND the proof that it’s valid
• Your browser verifies the proof locally
• Secure connection established instantly

Think of it like a restaurant displaying its current health inspection certificate in the window – you can see it’s valid without having to call the health department yourself.

Key Advantages

• Blazing Fast: No extra network connections needed, so websites load faster.
• Perfect Privacy: Certificate authorities can’t track which websites you visit.
• Rock Solid Reliability: Works even if the certificate authority’s servers are down.
• Mobile Friendly: Fewer network requests mean better performance on mobile devices.

Why OCSP Stapling is the Future

• Best of All Worlds: Combines the speed advantages of CRL with the freshness of OCSP, while solving both methods’ problems.
• Industry Adoption: Major websites and browsers are rapidly adopting this as the preferred method.
• Performance Requirements: Modern web users expect instant loading, making the speed benefits essential.
• Privacy Regulations: Growing privacy concerns make the surveillance aspects of traditional OCSP unacceptable.

The Bottom Line

OCSP Stapling represents the evolution of certificate validation – it’s faster than old methods, more private than OCSP, and more reliable than both. It’s like upgrading from dial-up internet to broadband: once you experience the improvement, you never want to go back.

For website owners: Enabling OCSP Stapling provides immediate benefits to your users and prepares you for future security requirements.

For internet users: You benefit automatically through faster, more private, and more reliable browsing when websites implement this properly.