According to the CISSP All-in-One Exam Guide2, a characteristic of the initialization vector when using Data Encryption Standard (DES) is that it can be transmitted in the clear as a random number. An initialization vector (IV) is a value or a parameter that is used to initialize or modify the encryption or decryption process, such as the cipher block chaining (CBC) mode of operation. An IV is used to provide an additional layer of security and randomness to the encryption or decryption process, as it prevents the same plaintext from producing the same ciphertext, and vice versa. An IV can be transmitted in the clear as a random number, as it does not contain any sensitive or confidential information, and as it changes with each session or transaction, making it difficult for the attackers to predict or manipulate the encrypted or decrypted data patterns. An IV must be known to both sender and receiver is not a characteristic of the initialization vector when using Data Encryption Standard (DES), as it is a requirement or a condition for the initialization vector when using any symmetric encryption algorithm, not a specific characteristic for DES. A symmetric encryption algorithm is an encryption algorithm that uses the same key for both encryption and decryption, such as DES, Triple DES, or Advanced Encryption Standard (AES). A symmetric encryption algorithm requires that the IV must be known to both sender and receiver, as it is needed for both encryption and decryption, and as it is used to synchronize the encryption or decryption process between the sender and the receiver. An IV must be retained until the last block is transmitted is not a characteristic of the initialization vector when using Data Encryption Standard (DES), as it is a requirement or a condition for the initialization vector when using any block cipher algorithm, not a specific characteristic for DES. A block cipher algorithm is an encryption algorithm that divides the plaintext or the ciphertext into fixed-length blocks, and encrypts or decrypts each block separately, such as DES, Triple DES, or AES. A block cipher algorithm requires that the IV must be retained until the last block is transmitted, as it is used to link or chain the blocks together, and as it is needed for the encryption or decryption of the last block. An IV can be used to encrypt and decrypt information is not a characteristic of the initialization vector when using Data Encryption Standard (DES), as it is a function or a purpose of the initialization vector when using any encryption algorithm, not a specific characteristic for DES. An encryption algorithm is a mathematical function or procedure that transforms the plaintext or the original data into the ciphertext or the encrypted data, and vice versa, using a key or a parameter, such as DES, Triple DES, AES, or Rivest-Shamir-Adleman (RSA). An encryption algorithm uses the IV to encrypt and decrypt information, as it is a value or a parameter that is used to initialize or modify the encryption or decryption process, and as it provides an additional layer of security and randomness to the encryption or decryption process. References: 2
