Information Security .

Based on Cryptography and Network Security book chapter 4.

Question 4.11:

Answer the following and explain your answer clearly at each step. Especially b,e.

uld want the the final 32-bit swap in the enci following equality to hold: Does it? The following problems refer to details of DES that are dese Consider the substitution defined by row 1 of S-box S. in diagram similar to Figure 4.2 that corresponds to this su Note: 9 45 at the output of the first round of the DES of all ones and the exter- 4.10 Com decryption, assuming that the ciphertext block is compose er 4, 17,41, and nal key is composed of all ones. This problem provides a numerical example of encryption using a of DES. We start with the same bit pattern for the key K and the pa one-round version plaintext, namely 4.11 . Hexadecimal notation: Binary notation: 0123456789ABCDEF 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111 a. Derive Ki, the first-round subkey. b. Derive Lo,Ro c. Expand Ro to get E[Ro], where E[ ] is the expansion function of Table S.1. d. Calculate A = E[RJKi. e. Group the 48-bit result of (d) into sets of 6 bits and evaluate the corresponding 0- S-box substitutions. t. Concatenate the results of (e) to get a 32-bit result, B. 9.4PPlu permutation to PB net PUB) 9 aPPlu permutation to (i)wright cipher text h-clculate R.- RN9 L