Question: What is a mandatory critical extension in an SEG (Security Gateway) certificate, as per Network Domain Security (NDS) Authentication Framework (AF) requirements?
Option 1: Key Usage with at least digitalSignature or nonRepudiation bits set
Option 2: Subject Alternative Name (subjectAltName) with DNS name
Option 3: Authority Key Identifier for cross-certification
Option 4: Extended Key Usage for client authentication
Explanation: In the context of SEG certificates for NDS/AF, ensuring the integrity and authenticity of digital signatures or preventing repudiation is crucial. Thus, setting at least the digitalSignature or nonRepudiation bits in the Key Usage extension is mandated critically to ensure these security aspects are enforced.