What is the primary function of the initialization vector (IV) in encryption?

The primary function of the initialization vector (IV) in encryption is to increase randomness in encryption. An IV is used alongside a secret key during the encryption process, particularly in certain modes of operation like Cipher Block Chaining (CBC) and Counter (CTR) modes. The IV ensures that even when the same plaintext is encrypted multiple times with the same key, the resulting ciphertext will be different each time. This randomness helps prevent attackers from discovering patterns in the encrypted data, thus enhancing the overall security of the cryptographic system.

In this context, while other options touch on important concepts in cryptography, they do not accurately describe the role of the IV. For instance, the IV is not a secret key, nor does it encrypt data blocks directly; instead, it serves as a randomizing element combined with the key to produce unique ciphertext outputs. Additionally, the IV does not ensure data integrity but relates more to confidentiality by adding randomness to the encryption process. Therefore, the choice highlighting the IV's role in increasing randomness accurately reflects its crucial function in cryptographic operations.