Stream Cipher: Characteristics and Uses
Question
Which of the following statements about a stream cipher are true? Each correct answer represents a complete solution.
Choose three.
Answers
Explanations
Click on the arrows to vote for the correct answer
A. B. C. D. E.ADE.
A stream cipher is a type of encryption algorithm that operates on individual bits of plaintext, as opposed to blocks of plaintext like a block cipher. It uses a pseudorandom keystream that is combined with the plaintext to produce the ciphertext. The keystream is generated by a key and an initialization vector (IV) that are shared between the sender and receiver.
Let's examine each statement to determine which are true about a stream cipher:
A. It typically executes at a higher speed than a block cipher. This statement is generally true. Stream ciphers are usually faster than block ciphers because they encrypt data one bit at a time, while block ciphers encrypt data in fixed-size blocks (e.g., 64 bits or 128 bits). However, the exact speed depends on the specific implementation of the cipher.
B. It divides a message into blocks for processing. This statement is false. Stream ciphers do not divide messages into blocks for processing; instead, they encrypt the message one bit at a time.
C. It typically executes at a slower speed than a block cipher. This statement is generally false. As mentioned in A, stream ciphers are usually faster than block ciphers because they process data one bit at a time. However, the exact speed depends on the specific implementation of the cipher.
D. It divides a message into bits for processing. This statement is true. Stream ciphers encrypt messages one bit at a time.
E. It is a symmetric key cipher. This statement is true. Stream ciphers are a type of symmetric key cipher, which means that the same key is used for both encryption and decryption.
In summary, statements A, D, and E are true about a stream cipher. Stream ciphers are fast because they encrypt data one bit at a time, they process messages one bit at a time, and they use the same key for encryption and decryption. Statement B is false because stream ciphers do not divide messages into blocks for processing. Statement C is generally false because stream ciphers are usually faster than block ciphers, although the exact speed depends on the specific implementation.
