Information security.

Based on cryptography and network security book , chapter 4.

Question number 4.11

Answer and explain the answer step by step especially b and e.

ould want the f ollowing equality to hold: Does it? ote: The following problems refer to details of DES that are dese Consider the substitution defined by row 1 of S-box S diagram similar to Figure 4.2 that corresponds to this substitu Compute the bits number 4, 17,41, and 45 at the output of decryption, assuming that the ciphertext block is compose nal key is composed of all ones and 45 at the output of the first round of the DES of all ones and the exter- 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 4.11 one-round version 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 e. Expand Ro to get ERo]. where El-] is the expansion function of Table S.1. d. Calculate A=E[R]KI. Group the 48-bit result of (d) into sets of 6 bits and evaluate the corresponding S-box substitutions. e. . Concatenate the results of (e) to get a 32-bit result, B. 9 4pPly permntat ion et PB)