What is the purpose of ensuring KEKs are strong relative to data keys?

What is the purpose of ensuring KEKs are strong relative to data keys?

• A. To ensure that if the KEK is compromised, data keys are still protected
• B. To allow weaker KEKs
• C. To meet a vendor's requirement only
• D. To reduce performance requirements

Answer: (A)

The main idea here is defense in depth through envelope encryption: data is encrypted with data keys, and those data keys are themselves encrypted (wrapped) by a key encryption key. Making the KEK strong relative to the data keys raises the barrier so that a breach of the KEK does not immediately expose the data keys and, consequently, the encrypted data. In other words, a robust KEK helps ensure that even if someone gains access to the KEK, obtaining usable data keys remains difficult, keeping the data protected for longer and slowing down any potential breach. The other options miss this protective purpose: weaker KEKs aren’t desirable, vendor-only requirements aren’t the point, and reducing performance is a side effect that would not be the goal of strong KEKs.

The main idea here is defense in depth through envelope encryption: data is encrypted with data keys, and those data keys are themselves encrypted (wrapped) by a key encryption key. Making the KEK strong relative to the data keys raises the barrier so that a breach of the KEK does not immediately expose the data keys and, consequently, the encrypted data. In other words, a robust KEK helps ensure that even if someone gains access to the KEK, obtaining usable data keys remains difficult, keeping the data protected for longer and slowing down any potential breach. The other options miss this protective purpose: weaker KEKs aren’t desirable, vendor-only requirements aren’t the point, and reducing performance is a side effect that would not be the goal of strong KEKs.