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# code in R and submit your script and results for each of the following. Use the functions expand() and S1_function() to do the following:

code in R and submit your script and results for each of the following. Use the functions **expand()** and **S1_function()** to do the following:

1. form second function for substitution box **S2_function()** that replicates the **S1_function() ** your wrote for homework 4 except that it uses the following substitution boxes: S11 contains the binary of the numbers (4, 0, 6, 5, 7, 1, 3 2) and S12 contains those for (5, 3, 0, 7, 6, 2, 1, 4). (20 points)

2. form a round function called **round1()** that takes a binary character vector of length 12 and key K of length 9 and does the following: (20 points total)

a. Divide the block into two equal halves called L0 and R0.

b. Create two sub keys K1 containing the first 8 digits of K and K2 that contains the last 8 digits of K.

c. Expand R0 from 6 t o 8 bits and call it ER0.

d. Take the XOR of the result of ER0 with K1. Store the first 4 bits in a variable called block1 and the last 4 bits in a variable called block2.

e. Call S1_function with block1 as its parameter.

f. Call S2_function with block2 as its parameter.

g. Concatenate the results of e) and f) and store the result in a variable called FR0.

h. Take the XOR of FR0 and L0 and store the results in R1.

i. Store R0 to L1.

j. Return L1 concatenated to R1.

3. form a second function called **round2() **that is similar to **round1() ** except that it uses K2 and returns the concatenation of R2 and L2.

4. Encrypt the message" "Wire $2000 to Bob" using the functions you wrote above following the simplified DES discussed in the class.

5. Modify the functions **round1()** and **round2() **such that they can be used for decryption. [Hint: for decryption use K2 instead of K1 for **round1()** and K1 instead of K2 for **round2()**. Use a third parameter in the two functions **round1()** and **round2() **to indicate whether you are encrypting or decrypting].