(What is a characteristic of Cipher Block Chaining (CBC) mode in cryptography?

CBC mode introduces chaining between blocks to prevent the pattern leakage inherent in ECB. In CBC, each plaintext block is XORed with the previous ciphertext block before being encrypted with the block cipher. For the first block, CBC uses an Initialization Vector (IV) to serve as the “previous ciphertext” input. This makes encryption of each block dependent on the previous block’s ciphertext, which is exactly the defining characteristic described in option A. CBC does not generate a continuous stream of key material—that describes stream ciphers or stream-like modes such as CTR/OFB. CBC also does not require a different key per operation; the same symmetric key is reused, while the IV must be fresh/unpredictable to ensure semantic security. The block size is determined by the underlying block cipher (e.g., AES is 128-bit blocks, DES/3DES are 64-bit blocks), not a fixed 32-bit size for CBC itself. Because CBC is not inherently authenticated, best practice is to pair it with a MAC (Encrypt-then-MAC) or use an AEAD mode instead.