Which of the following authentication device credentials is the most difficult to revoke when an...

Comprehensive and Detailed In-Depth Explanation:

Biometric authentication (e.g., fingerprint, retina scan) is the most difficult to revoke because it is linked to an individual’s physical attributes, which cannot be changed like passwords or physical devices.

Option A (Traditional key lock) – Can be revoked by retrieving the key or changing the lock.

Option C (Card-key system) – Can be revoked by deactivating the card.

Option D (Proximity device) – Can be revoked by disabling the device.

Since biometric data is permanently tied to an individual, revoking access is complex, making Option B the correct answer.