Which one of the following is an algorithm that uses variable length key from 1 to 256 bytes, which constitutes a state table that is used for subsequent generation of pseudorandom bytes and then a pseudorandom string of bits, which is XORed with the plaintext to produce the ciphertext?

Which one of the following is an algorithm that uses variable length key from 1 to 256 bytes, which constitutes a state table that is used for subsequent generation of pseudorandom bytes and then a pseudorandom string of bits, which is XORed with the plaintext to produce the ciphertext?
A . PIKE
B. Twofish
C. RC4
D. Blowfish

View Answer

Answer: C

Explanation:

RC4

https://en.wikipedia.org/wiki/RC4

RC4 (Rivest Cipher 4 also known as ARC4 or ARCFOUR meaning Alleged RC4, see below) is a stream cipher. While it is remarkable for its simplicity and speed in software, multiple vulnerabilities have been discovered in RC4, rendering it insecure. It is especially vulnerable when the beginning of the output keystream is not discarded, or when nonrandom or related keys are used. Particularly problematic uses of RC4 have led to very insecure protocols such as WEP.

The key-scheduling algorithm is used to initialize the permutation in the array "S". "keylength" is defined as the number of bytes in the key and can be in the range 1 keylength 256, typically between 5 and 16, corresponding to a key length of 40 C 128 bits. First, the array "S" is initialized to the identity permutation. S is then processed for 256 iterations in a similar way to the main PRGA, but also mixes in bytes of the key at the same time.