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Which of the following statements pertaining to stream …

Which of the following statements pertaining to stream ciphers is TRUE?

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A.
A stream cipher is a type of asymmetric encryption algorithm.

B.
A stream cipher generates what is called a keystream.

C.
A stream cipher is slower than a block cipher.

D.
A stream cipher is not appropriate for hardware-based encryption.

Explanation:
A stream cipher is a symmetric key cipher where plaintext digits are combined with a pseudorandom cipher
digit stream (keystream). In a stream cipher each plaintext digit is encrypted one at a time with the
corresponding digit of the keystream, to give a digit of the ciphertext stream. Since encryption of each digit is
dependent on the current state of the cipher, so it is also known as state cipher. In practice, a digit is typically a
bit and the combining operation an exclusive-or (XOR).
The pseudorandom keystream is typically generated serially from a random seed value using digital shift
registers. The seed value serves as the cryptographic key for decrypting the ciphertext stream.
Stream ciphers typically execute at a higher speed than block ciphers and have lower hardware complexity.
However, stream ciphers can be susceptible to serious security problems if used incorrectly; in particular, the
same starting state (seed) must never be used twice.
Incorrect Answers:
A: A stream cipher is not a type of asymmetric encryption algorithm; it is a symmetric key cipher.
C: A stream cipher is not slower than a block cipher; it is faster.
D: Stream ciphers require a lot of randomness and encrypt individual bits at a time. This requires more
processing power than block ciphers require, which is why stream ciphers are better suited to be implemented
at the hardware level.

https://en.wikipedia.org/wiki/Stream_cipher


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