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.