SSL Cert Downloads Explained: CA Certificates vs. Website Public Certificates

When dealing with SSL/TLS certificates, the term “downloading a certificate” can mean different things depending on the context. Two common scenarios often cause confusion: the need to Download CA Certificate files (usually intermediates) for server setup, and the action to Download Website’s Public Certificate for inspection or verification. Understanding the distinct purpose and process for each is crucial for website administrators and security-conscious users alike.

This post clarifies what each type of download entails, who needs it, why, and how to perform it, ensuring you get the right certificate files for the right task.

Key Takeaways: CA Certs vs. Public Certs

• CA Certificate Download: Refers to obtaining Root and Intermediate certificates from the Certificate Authority (like sslrepo.com or the issuing CA like Sectigo, DigiCert). Needed by server administrators to install on their own web server to complete the trust chain.
• Website Public Certificate Download: Refers to saving the SSL certificate currently being used by a remote website you are visiting. Usually done by end-users, developers, or security analysts for verification, troubleshooting, or information gathering.
• Purpose Distinction: CA certs are for building trust on your server; a website’s public cert is for verifying trust on someone else’s server.
• Source Difference: CA certs come from the issuer; a website’s public cert comes directly from the web server during the TLS handshake.

Scenario 1: Download CA Certificate (Root & Intermediate)

What are CA Certificates?

Certificate Authorities (CAs) structure trust using a hierarchy.

• Root CA Certificates: Pre-installed and trusted by browsers and operating systems. They form the anchor of trust.
• Intermediate CA Certificates: Issued by Root CAs, these act as intermediaries to issue end-entity server certificates (the ones you buy for your domain). They create a “chain of trust” linking your server certificate back to the trusted root. ^^(Reference: SSL/TLS Trust Chain Principles)

Why Download Them?

When you install an SSL certificate on your web server (like Apache, Nginx, IIS), you usually need to install the corresponding Intermediate CA certificate(s) as well. Without them, browsers visiting your site cannot validate the chain back to a trusted root and may display a security warning, even if your main certificate is valid.

Who Needs Them?

• Website Administrators
• Server Managers
• Anyone responsible for installing or configuring SSL/TLS certificates on a web server.

How to Download CA Certificates?

1. From Your Provider: When you purchase an SSL certificate from sslrepo.com or directly from a CA, the necessary intermediate certificates are typically provided:
   • In the Issuance Email: Often attached or linked directly.
   • In Your Account Panel: Available for download within your customer dashboard.
   • On the CA’s Website: Most CAs maintain a public repository of their Root and Intermediate certificates, usually categorized by product type. Look for sections labeled “Repository,” “Support,” or “Downloads.” ^^(Reference: Standard CA Certificate Repository Practices)
2. Common Formats: Intermediate certificates are usually provided as .crt, .cer, or .pem files. Sometimes they are bundled together in a single file often called ca-bundle.crt.

Scenario 2: Download Website’s Public Certificate

What is a Website’s Public Certificate?

This is the actual end-entity SSL/TLS certificate that a specific website (e.g., www.example.com) presents to your browser when you connect via HTTPS. It contains the website’s public key, identifying information (like the domain name), the issuer’s details, and the validity period. It does not contain the website’s private key (which must remain secret on the server).

Why Download/View It?

• Verification: To manually check the certificate details (domain name coverage, expiry date, issuer).
• Troubleshooting: To diagnose connection errors or trust issues.
• Security Analysis: To inspect the certificate chain, signature algorithms, or key usage.
• System Configuration: Sometimes needed to import into specific client applications or trust stores to allow connections to that server (less common for public websites, more for internal systems).

Who Might Do This?

• End Users experiencing connection warnings.
• Web Developers debugging HTTPS setup.
• Network Administrators or Security Professionals investigating a site.
• System Integrators configuring specific client software.

How to Download a Website’s Public Certificate?

The easiest way is using your web browser:

(Example using Google Chrome – steps are similar in Firefox, Edge)

1. Navigate to the HTTPS Site: Go to the website (e.g., https://www.google.com).
2. Click the Padlock Icon: In the address bar, click the padlock icon (usually to the left of the URL).
3. View Certificate Information: Click on “Connection is secure” (or similar wording), then click on “Certificate is valid” (or similar). This opens the browser’s certificate viewer.
4. Go to Details Tab: Switch to the “Details” tab (or equivalent).
5. Export/Copy to File: Look for an “Export…” or “Copy to File…” button.
6. Choose Format: You’ll often be prompted to choose an export format.
   • Base64-encoded X.509 (.CER or .CRT): A common text-based format. Good for general use.
   • DER encoded binary X.509 (.CER or .CRT): A binary format.
   • (Optional) Cryptographic Message Syntax Standard – PKCS #7 Certificates (.P7B): This option might include the intermediate certificates if the server sent them and the browser captured them. Check the option “Include all certificates in the certification path if possible.”
7. Save the File: Choose a location and filename to save the certificate.

Alternative (Advanced): Using OpenSSL

You can use the command-line tool OpenSSL (if installed) to retrieve a site’s certificate:

openssl s_client -connect www.example.com:443 -showcerts </dev/null 2>/dev/null | openssl x509 -outform PEM > website_certificate.pem

• Replace www.example.com with the target domain.
• This command connects, displays certificate info, filters out just the certificate part in PEM format, and saves it to website_certificate.pem.

Why the Distinction Matters

Mixing up these two actions can lead to problems:

• Trying to install a downloaded website public certificate from another site onto your server won’t work – you don’t have the corresponding private key, and it’s issued for a different domain.
• Forgetting to Download CA Certificate (intermediates) for your own server installation will cause trust errors for your visitors.

Wrapping It Up

Understanding the difference between downloading CA (intermediate/root) certificates and downloading a specific website’s public certificate is key to managing SSL/TLS effectively. Server administrators need to Download CA Certificate files from their provider (like sslrepo.com) to ensure their server presents a complete trust chain. Anyone can Download Website’s Public Certificate using a browser or tools like OpenSSL primarily for inspection and verification purposes. Knowing which one you need and where to get it simplifies troubleshooting and ensures proper security configurations.

Frequently Asked Questions (FAQ)

• Q1: I bought a certificate from sslrepo.com. Where do I download the intermediate CA certificates?
  Check the certificate issuance email you received. Alternatively, log in to your sslrepo.com account dashboard or visit their support/resource section, which should provide the necessary CA bundle or intermediate files for your specific certificate type.
• Q2: Can I install the public certificate I downloaded from www.example.com onto my own server, www.mysite.com?
  No. A website’s public certificate is cryptographically tied to its specific domain(s) and its private key (which you don’t have). You need to obtain a certificate specifically issued for www.mysite.com through a proper CSR generation and CA validation process.
• Q3: How can I check if my own web server is correctly sending the intermediate CA certificates?
  Use an online SSL checker tool (like Qualys SSL Labs, DigiCert SSL Checker). These tools analyze your server’s configuration and will report “Chain issues” if intermediates are missing or incorrect. You can also check the certification path details shown in a browser when visiting your site.
• Q4: What file formats are certificates usually in?
  Common formats include:
  • .PEM: Base64 encoded, often includes -----BEGIN CERTIFICATE----- markers. Can contain single or multiple certificates (chain). Text-based.
  • .CER / .CRT: Can be Base64 (like PEM) or binary DER encoded. Often used for single certificates.
  • .DER: Binary encoded format.
  • .P7B / .PKCS7: A container format, often Base64 encoded, typically used to distribute multiple certificates (server cert + intermediates) but without the private key.
• Q5: I downloaded a website’s public certificate, but my browser still shows a warning for that site. Why?
  Downloading the certificate just saves a copy. The warning could be due to several reasons unrelated to the download itself:
  • The certificate chain is incomplete (missing intermediates on their server).
  • The certificate has expired.
  • The certificate name doesn’t match the visited domain (Name Mismatch Error).
  • The certificate has been revoked by the CA.
  • Your system clock is incorrect.
  • The site uses outdated security protocols/ciphers.