Which of the following is not a characteristic of a strong stream cipher?

A.
Unbiased keystream

B.
Long periods of no repeating patterns within keystream

C.
Best used in software implementations

D.
Statistically unpredictable

Explanation:
For a stream cipher to be strong against cryptanalysis attacks it
should contain the other mentioned characteristics. Block ciphers work better in
software implementations because they work with blocks of data; stream ciphers work
better within hardware because they work with one bit at a time and are resource
intensive.