Retrieving plain text from Cryptographic text and random values

[zak100]

Hi,

I am trying to understand the following question:

 

In a 3-bit block cipher, suppose a sender transmits a cipher text including c(1), r(1), c(2), r(2), c(3), r(3) to a receiver. Find the original plaintext at the receiver. Here c(1) = 100, r(1) = 001, c(2) = 010, r(2)= 111, c(3) = 000, and r(3) = 100. A block cipher encryption key table (Ks) is also shown below:

 

The answer for the first case is:

M(1) = Ks(c(1) XOR r(1) = Ks(100) XOR 001 = 010

From the table, the output corresponding to 100 to 011.

But the above answer is 010. I can't understand this.

 

Somebody please guide me.

 

Zulfi.

Edited June 4, 2020 by zak100