Sally is responsible for key management within her organization. Which of the following incorrectly describes a principle of secure key management?

A.
Keys should be backed up or escrowed in case of emergencies.

B.
The more a key is used, the shorter its lifetime should be.

C.
Less secure data allows for a shorter key lifetime.

D.
Keys should be stored and transmitted by secure means.

Explanation:
C: Key management is critical for proper protection. Part of key management is determining the lifespan of keys. The key’s lifetime should correspond with the sensitivity of the data
it is protecting. Less secure data may allow for a longer key lifetime, whereas more sensitive data might require a shorter key lifetime. Keys should be properly destroyed when their
lifetime comes to an end. The processes of changing and destroying keys should be automated and hidden from the user. They should be integrated into software or the operating
system. It only adds complexity and opens the doors for more errors when processes are done manually and depend upon end users to perform certain functions.
A is incorrect because it is true that keys should be backed up or escrowed in case of emergencies. Keys are at risk of being lost, destroyed, or corrupted. Backup copies should be
available and easily accessible when required. If data are encrypted and then the user accidentally loses the necessary key to decrypt it, this information would be lost forever if there
were not a backup key. The application being used for cryptography may have key recovery options, or it may require copies of the keys to be kept in a secure place.
B is incorrect because it is true that the more a key is used, the shorter its lifetime should be. The frequency of use of a cryptographic key has a direct correlation to how often the
key should be changed. The more a key is used, the more likely it is to be captured and compromised. If a key is used infrequently, then this risk drops dramatically. The necessary
level of security and the frequency of use can dictate the frequency of key updates. A mom-and-pop diner might only change its cryptography keys every month, whereas an
information warfare military unit might change them every day or every week.
D is incorrect because it is true that keys should be stored and transmitted by secure means. Keys are stored before and after distribution. When a key is distributed to a user, it
needs a secure place within the file system to be stored and used in a controlled method. The key, the algorithm that will use the key, configurations, and parameters are stored in a
module that also needs to be protected. If an attacker is able to obtain these components, she could masquerade as another user and decrypt, read, and re-encrypt messages not
intended for her.