ITP4103 2.2 DES Encryption

 

Questions

1.	The diagram on the next page shows the internal work flow of Feistel function in DES and the table of (S1-S8) boxes.  The Feistel function consists of four stages: expansion (E), key mixing (Å), substitution (S1-S8) and permutation (P).  By using the tables provided, find out the output after substitution, if the output from key mixing is: 001010 100101 101001 111010 101101 010010 001100 110010
2.	The diagram on the next page shows the work flow of DES and the bit mapping of the Initial Permutation (IP).  Plaintext will do transposition in the Initial Permutation (IP).  Then the output will feed into 16 the Feistel function (F) and repeat for 16 rounds.  Finally the data will go through the Final Permutation (FP) to produce the encrypted data.  By using the diagram provided, find out the output after the Initial Permutation (IP). If the plaintext is: 00101010 10010101 10100101 11100110 10011101 01011010 00001100 11011010
3.	The diagram shows the internal work flow of Feistel function in DES and the table of (S1-S8) boxes.  The Feistel function consists of four stages: expansion (E), key mixing (Å), substitution (S1-S8) and permutation (P).  Find the output after expansion.  The input is given as follows: 0110 0101 1001 1110 1101 0010 0100 1011
4.	The diagram below shows the internal work flow of Feistel function in DES and the table of (S1-S8) boxes.  The Feistel function consists of four stages: expansion (E), key mixing (Å), substitution (S1-S8) and permutation (P).  By using the tables provided, find out the output after substitution, if the output from key mixing is: 011010 101001 010010 110110 100011 011001 010110 100110
5.	The diagram shows the internal work flow of Feistel function in DES and the table of (S1-S8) boxes.  The Feistel function consists of four stages: expansion (E), key mixing (Å), substitution (S1-S8) and permutation (P).  Find the output after permutation   The output from the S-box are as follows: S1 S2 S3 S4 S5 S6 S7 S8 14 7 12 6 3 8 5 9 Suggested Solution(Non-official): Q1 1111 1010 0110 0010 0010 1101 1000 0110  Q2 1010 1000 1011 0010 0101 1110 0001 0110 1001 1110 0000 1101 1111 0001 1010 1001  Q3 101100 001011 110011 111101 011010 100100 001001 010110 Q4 1001 0011 1101 1110 1000 0000 0111 0001 Q5 0111 1010 1101 0001 1101 1011 1001 0000 For any error, please comment below to help to correction. Thanks a lot.