Question 1
In Figure 1, there is one step missing between the F routine and the FP routine. Find out and explain what the missing step is.
Question 2
Using Figure 1, write the algorithm of the DES encryption (including the missing step in Q1) in pseudocode.
Question 3
Figure 1 also shows three routines/modules (IP, F and FP) with input (plaintext) and output (ciphertext) in the main DES cryptosystem. Write the algorithm for: IP and FP.
Question 4
Figure 2 shows the details of the F routine of the DES algorithm. Write the algorithm of the F routine in pseudocode; 6
Question 5
The F routine consists of Question 1 (1%; not more than 0.5 page)
In Figure 1, there is one step missing between the F routine and the FP routine. Find out and explain what the missing step is.
Question 2
Using Figure 1, write the algorithm of the DES encryption (including the missing step in Q1) in pseudocode.
Question 3
Figure 1 also shows three routines/modules (IP, F and FP) with input (plaintext) and output (ciphertext) in the main DES cryptosystem. Write the algorithm for: IP and FP.
Question 4
Figure 2 shows the details of the F routine of the DES algorithm. Write the algorithm of the The F routine consists of 3 lookup tables:E-table, S-Box and P-Box. Using the Internet/Library resources, find these tables and summarise in a few lines what the tables are all about. For each lookup table, give an example of input and the resulting output.
Question 6
However, Figure 2 does not show how Subkey (48 bits) is generated from the key-mixing(also known as subkey generation) stage. Use the Internet/Library Resources to find more about the key-mixing stage and write in pseudocode steps the algorithm of this key-mixing
stage.
Question 7
Deriving from Figure 1 (including the missing step from Q1), show the steps in pseudocode how DES decryption works.