.NET Architecture & System Design Interview Question #157

What is mutual TLS (mTLS)?

Security Architecture, Multi-Tenancy & Disaster Recovery Senior Advanced

Quick Interview Answer

Mutual TLS authenticates both sides of a TLS connection with certificates. The server presents its certificate as usual, and the client also presents a certificate that the server validates.

Detailed Explanation

Mutual TLS authenticates both sides of a TLS connection with certificates. The server presents its certificate as usual, and the client also presents a certificate that the server validates.

mTLS can provide strong service-to-service identity, especially in controlled environments. Certificate issuance, rotation, revocation, trust chains, and operational automation are essential for using it safely at scale.

Code Example

Service A -- mTLS --> Service B

A validates B certificate
B validates A certificate