Digital certificate and Mutual TLS
A digital certificate is like an online identity card, issued by a Certificate Authority (CA) (like Digicert and other). It helps verify the identity of a server or client during encrypted communication (like HTTPS or mTLS).
Digital certificate contains
- Public key of the owner (server/client)
- Identity details (e.g., domain, organization)
- Expiry date
- CA’s digital signature
Why Used
- To secure communication over the internet (e.g., HTTPS).
- To verify identity and avoid impersonation or man-in-the-middle attacks.
Regular TLS (used in HTTPS)
- Client verifies the server via its digital certificate.
- Server doesn’t care who the client is — anyone can access public pages.
Mutual TLS (mTLS)
- Both client and server verify each other's certificates.
- Enables two-way authentication.
- This adds an extra layer of trust and is commonly used in internal and secure systems.
Pros of mTLS
- Strong authentication (both parties verified)
- End-to-end encrypted channel
- Resistant to impersonation and MITM attacks
Cons of mTLS
- More complex setup
- Requires certificate rotation and management
- Not ideal for public user authentication (too heavy)
TLS vs Mutual TLS
| Feature | TLS (Standard HTTPS) | Mutual TLS (mTLS) |
|---|---|---|
| Who presents certificate? | Server only | Both client and server |
| Who verifies identity? | Client only | Both client and server |
| Client identity verified? | No | Yes |
| Use case | Public websites, browsers | Internal APIs, service-to-service |
| Setup complexity | Low | High |
| Security level | Good | Very Strong |