Question

Let s1 and s2 are the standard perμtation and Vigenere ciphers with a block length of 4. In the product cipher s1 x s2 with key k1 in the perμtation cipher given as 1 2 3 4 2 4 3 1, what is the key code k2?

a) 1 2 3 4
b) 4 3 2 1
c) 2 3 4 1
d) 3 4 1 2

Answer 1

The key code k2 for the combined permutation and Vigenere cipher with block length of 4, based on the provided permutation key k1, is most likely option (b) 4 3 2 1.

Step-by-step explanation:

The question is asking to determine the key code k2 for a product cipher that is the result of combining a standard permutation cipher s1 and a Vigenere cipher s2 with a block length of 4. Given the permutation key k1 as 1 2 3 4 2 4 3 1, we need to understand that in a permutation cipher, the key indicates the rearrangement of the positions of the characters. From the given k1, for a block length of 4, the second permutation would actually be a reverse from 4 to 1 (4 3 2 1).

Therefore, the most logical match for the second key code k2, which is applied in the Vigenere cipher part of the product cipher, would be option (b) 4 3 2 1, matching the reverse order indicated in the second half of key k1.