Types of digital certificates

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Types of digital certificates

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Digital certificates are essential for secure digital communication, particularly for encryption, authentication, and integrity. These certificates are based on Public Key Infrastructure (PKI) and are issued by Certificate Authorities (CAs). Here’s an overview of the main types of certificates and their purposes:

SSL/TLS Certificates #

Used to secure communication between web servers and browsers (HTTPS). Types:

Domain Validation (DV) #

  • Validates domain ownership only.
  • Fast and inexpensive.

Example: personal websites or blogs.

Organization Validation (OV) #

  • Validates domain ownership and organization identity.
  • Better trust level, used for small to medium businesses.

Extended Validation (EV) #

  • Most rigorous verification of identity and legal existence.
  • Shows company name in the address bar (in some browsers).

Example: banking and e-commerce sites.

Wildcard Certificates #

  • Secure a domain and all its subdomains (e.g., *.example.com).

Multi-Domain (SAN/UCC) Certificates #

  • Secure multiple fully qualified domain names with one certificate.

Code Signing Certificates #

Used by developers to digitally sign software, ensuring the code hasn’t been altered or tampered with after signing.

  • Standard Code Signing – Verifies the publisher and ensures code integrity.
  • EV Code Signing – Adds stricter verification, and helps avoid Windows SmartScreen warnings.

Email Certificates (S/MIME) #

Used to digitally sign and encrypt email messages.

  • Ensures authenticity of sender.
  • Prevents eavesdropping and spoofing.

Example: corporate email communications, legal or medical data.

Client Certificates #

Used to authenticate clients (users or devices) to servers.

  • Works like a user password, but with stronger cryptography.
  • Common in VPNs, secure APIs, mTLS, and enterprise networks.

Root and Intermediate Certificates #

Part of the certificate trust chain:

  • Root Certificate – Top-level certificate trusted by systems (pre-installed in OS/browsers).
  • Intermediate Certificate – Issued by root, used by CAs to issue end-entity certificates.

This chain of trust allows browsers to verify a website’s certificate by following the path back to a trusted root.

Self-Signed Certificates #

Created and signed by the same entity.

  • Used in internal systems or development environments.
  • Not trusted by default (cause warnings in browsers).

Comparison Table of Digital Certificate Types #

Certificate Type Purpose Identity Validation Common Use Case Trusted by Browsers
DV SSL Secure websites (basic HTTPS) Domain only Blogs, personal sites Yes
OV SSL Secure websites (verified org) Domain + Org Business websites Yes
EV SSL High-trust secure websites Domain + Legal Org Banks, e-commerce Yes
Wildcard SSL Secure all subdomains Varies Large websites with many subdomains Yes
SAN / UCC Secure multiple domains Varies Multi-site hosting, Exchange servers Yes
Code Signing Sign software/code Org or Individual Software publishers Not browser-based
EV Code Signing Sign code with SmartScreen support Extended Org check Enterprise software vendors Not browser-based
S/MIME Email Secure email (sign/encrypt) Email + Identity Corporate and legal email With config
Client Auth Authenticate users/devices Client identity VPN, APIs, internal apps Not browser-based
Root Certificate Trust anchor for CA hierarchy N/A (pre-installed) Trusted CAs (e.g., DigiCert, Let’s Encrypt) Yes
Intermediate Cert Link root and end-entity certs Issued by root CA CA-managed issuance Yes
Self-Signed Cert Local/development use None (self-issued) Dev, internal testing No

Trust Chain Diagram #

+----------------------------+
|     Trusted Root CA       |
| (Pre-installed in systems)|
+------------+--------------+
             |
             v
+----------------------------+
|  Intermediate CA (1..n)   |
| (Issued by Root CA)       |
+------------+--------------+
             |
             v
+----------------------------+
|  End-Entity Certificate    |
| (Website, client, email)   |
|  - DV, OV, EV, etc.        |
+----------------------------+

Browsers/clients validate the chain from leaf → intermediate → root.

For example, when visiting https://relianoid.com:

  • The browser receives the end-entity cert.
  • It checks that it’s signed by a known intermediate.
  • Then it ensures that intermediate is trusted via a root CA.
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