CompTIA Security+ Exam Prep

Answer: B - Cipher Block Chaining (CBC) prevents a pattern in Cipher Block Chaining mode by taking the value of one block and adding it to the next block value within the algorithm. This results in more random ciphertext. Ciphertext is extracted and used from the previous block of text. This provides dependence between the blocks, in a sense, chaining them together. This continues through the entire message and provides the necessary randomness that allows CBC to be used to encrypt large files and prevents an attacker from reverse-engineering and uncovering the key.