Which statement about encryption is true?

• A. It increases system performance.
• B. It compresses data to save space.
• C. It only protects data at rest, not in transit.
• D. It encodes data to unreadable form without keys, protecting confidentiality both when stored and transmitted.

Answer: (D)

Encryption transforms data into a scrambled, unreadable form so that only someone with the correct key can restore it to readable form. This protects confidentiality whether the data is stored (data at rest) or being sent over a network (data in transit). The key idea is that without the proper key, the information remains unreadable, so even if someone intercepts or steals it, they can’t understand it. This concept covers both storage and transmission, which is what makes it true.

Note that encryption doesn’t inherently improve system performance and isn’t about compressing data. It adds cryptographic processing overhead and isn’t primarily used for reducing data size.