Question: What security vulnerability could arise if an operator (M) creates certificates resembling another operator's (A) certificates, and how can this be mitigated in the context of Network Domain Security (NDS) Authentication Framework (AF)?
Option 1: By implementing a proprietary "AllowedCertificateSubject" check on the certificate's Subject field alone, ensuring only authorized operators access specific subnetworks.
Option 2: Through regular security audits and establishing strong legal bindings between operators, discouraging the fabrication of illegitimate certificates.
Option 3: Utilizing commonly supported PKI end-entity products with standard "AllowedCertificateSigner" properties to verify both Subject and Signer names.
Option 4: Implementing nameConstraints in the Bridge CA certificate issued to operator M, ensuring only specified names can be used in certificates, despite potential updates needed for new roaming agreements.
Explanation: The correct answer is Option 4 because implementing nameConstraints directly addresses the vulnerability by restricting the allowed names in certificates issued by an operator (e.g., Operator M), preventing them from fabricating certificates that mimic another operator's (e.g., Operator A) identity. This method technically prevents the exploit beforehand, unlike other options which either don't fully mitigate the risk (Option 1 and 3, due to limited support or effectiveness) or rely on non-technical deterrents (Option 2). While updating certificates for new roaming agreements might be necessary, this approach ensures a secure authentication framework.