In this lab, you will be working with a simplified – and not very secure – versi

Question

In this lab, you will be working with a simplified – and not very secure – version of one of the most popular Symmetric-key systems – DES. You can find the details here: http://www.cs.uri.edu/cryptography/dessimplified.htm
Illustrate the working of DES by completing the following fields. Input message is 010010100100 and the key is 010011110. Encryption Round 1 (i = 0) 1. L0= ____________________ and R0= ____________________ ; K1 = ____________________. 2. E(R0) = ____________________. 3. E(R0) K1 = ____________________ ____________________= ____________________. 4. S1(__________) = __________, S2(__________) = _________, f(R0,K1) = __________ 5. f(R0,K1) L0 = __________ __________= __________. 6. Now using the formulas Li = Ri-1 and Ri = Li-1 f (Ri-1, Ki), L1 =__________and R1 = __________. Round 2 (i = 1) 1. L1 = __________ and R1 = __________ ; K2 = __________. 2. E(R1) = __________. 3. E(R1) K1 = __________ __________= __________. 4. S1(__________) = __________; S2(__________) = __________; f(R1,K2) = __________ 5. f(R1,K2) L1 = __________ __________= __________. 6. Now using the formulas Li = Ri-1 and Ri = Li-1 f (Ri-1, Ki), L2 =_________ and R2 = __________. So encrypted message, R2 L2 = ___________________ Decryption Round 1(i = 0) 1. L0= __________ and R0= __________ ; K2 = __________. 2. E(R0) = __________. 3. E(R0) K1 = __________ __________= __________. 4. S1(__________) = __________; S2(__________) = __________; f(R0,K2) = __________ 5. f(R0,K2) L0 = __________ __________= __________. 6. Now using the formulas Li = Ri-1 and Ri = Li-1 f (Ri-1, Kn-i), L1 = _________and R1 = _________. Round 2 (i = 1) 1. L1 = __________and R1 = __________; K1 = __________. 2. E(R1) = __________. 3. E(R1) K1 = __________ __________= __________. 4. S1(__________) = __________; S2(__________) = __________; f(R1,K1) = __________ 5. f(R1,K1) L1 = __________ __________= __________. 6. Using the formulas Li = Ri-1 and Ri = Li-1 f (Ri-1, Kn-i), L2 = __________and R2 = __________. So decrypted message, R2 L2 =________________ , which SHOULD BE SAME as the original plaintext message.
In this lab, you will be working with a simplified – and not very secure – version of one of the most popular Symmetric-key systems – DES. You can find the details here: http://www.cs.uri.edu/cryptography/dessimplified.htm
Illustrate the working of DES by completing the following fields. Input message is 010010100100 and the key is 010011110. Encryption Round 1 (i = 0) 1. L0= ____________________ and R0= ____________________ ; K1 = ____________________. 2. E(R0) = ____________________. 3. E(R0) K1 = ____________________ ____________________= ____________________. 4. S1(__________) = __________, S2(__________) = _________, f(R0,K1) = __________ 5. f(R0,K1) L0 = __________ __________= __________. 6. Now using the formulas Li = Ri-1 and Ri = Li-1 f (Ri-1, Ki), L1 =__________and R1 = __________. Round 2 (i = 1) 1. L1 = __________ and R1 = __________ ; K2 = __________. 2. E(R1) = __________. 3. E(R1) K1 = __________ __________= __________. 4. S1(__________) = __________; S2(__________) = __________; f(R1,K2) = __________ 5. f(R1,K2) L1 = __________ __________= __________. 6. Now using the formulas Li = Ri-1 and Ri = Li-1 f (Ri-1, Ki), L2 =_________ and R2 = __________. So encrypted message, R2 L2 = ___________________ Decryption Round 1(i = 0) 1. L0= __________ and R0= __________ ; K2 = __________. 2. E(R0) = __________. 3. E(R0) K1 = __________ __________= __________. 4. S1(__________) = __________; S2(__________) = __________; f(R0,K2) = __________ 5. f(R0,K2) L0 = __________ __________= __________. 6. Now using the formulas Li = Ri-1 and Ri = Li-1 f (Ri-1, Kn-i), L1 = _________and R1 = _________. Round 2 (i = 1) 1. L1 = __________and R1 = __________; K1 = __________. 2. E(R1) = __________. 3. E(R1) K1 = __________ __________= __________. 4. S1(__________) = __________; S2(__________) = __________; f(R1,K1) = __________ 5. f(R1,K1) L1 = __________ __________= __________. 6. Using the formulas Li = Ri-1 and Ri = Li-1 f (Ri-1, Kn-i), L2 = __________and R2 = __________. So decrypted message, R2 L2 =________________ , which SHOULD BE SAME as the original plaintext message.
In this lab, you will be working with a simplified – and not very secure – version of one of the most popular Symmetric-key systems – DES. You can find the details here: http://www.cs.uri.edu/cryptography/dessimplified.htm
Illustrate the working of DES by completing the following fields. Input message is 010010100100 and the key is 010011110. Encryption Round 1 (i = 0) 1. L0= ____________________ and R0= ____________________ ; K1 = ____________________. 2. E(R0) = ____________________. 3. E(R0) K1 = ____________________ ____________________= ____________________. 4. S1(__________) = __________, S2(__________) = _________, f(R0,K1) = __________ 5. f(R0,K1) L0 = __________ __________= __________. 6. Now using the formulas Li = Ri-1 and Ri = Li-1 f (Ri-1, Ki), L1 =__________and R1 = __________. Round 2 (i = 1) 1. L1 = __________ and R1 = __________ ; K2 = __________. 2. E(R1) = __________. 3. E(R1) K1 = __________ __________= __________. 4. S1(__________) = __________; S2(__________) = __________; f(R1,K2) = __________ 5. f(R1,K2) L1 = __________ __________= __________. 6. Now using the formulas Li = Ri-1 and Ri = Li-1 f (Ri-1, Ki), L2 =_________ and R2 = __________. So encrypted message, R2 L2 = ___________________ Decryption Round 1(i = 0) 1. L0= __________ and R0= __________ ; K2 = __________. 2. E(R0) = __________. 3. E(R0) K1 = __________ __________= __________. 4. S1(__________) = __________; S2(__________) = __________; f(R0,K2) = __________ 5. f(R0,K2) L0 = __________ __________= __________. 6. Now using the formulas Li = Ri-1 and Ri = Li-1 f (Ri-1, Kn-i), L1 = _________and R1 = _________. Round 2 (i = 1) 1. L1 = __________and R1 = __________; K1 = __________. 2. E(R1) = __________. 3. E(R1) K1 = __________ __________= __________. 4. S1(__________) = __________; S2(__________) = __________; f(R1,K1) = __________ 5. f(R1,K1) L1 = __________ __________= __________. 6. Using the formulas Li = Ri-1 and Ri = Li-1 f (Ri-1, Kn-i), L2 = __________and R2 = __________. So decrypted message, R2 L2 =________________ , which SHOULD BE SAME as the original plaintext message.

Explanation / Answer

Input Message: 010010100100

Encryption:

Round 1 (i = 0)

1. L0= 010010 and R0= 100100 ;
K1 = 01001111.

2. E(R0) = 10101000.

3. E(R0) XOR K1 =10101000 XOR 01001111= 11100111.

4. S1(1110) = 101 , S2(0111) = 010,
f(R0,K1) = 101010

5. f(R0,K1) XOR L0 = 101010 XOR 010010= 111000.

6. Now using the formulas Li = Ri-1 and Ri = Li-1 f (Ri-1, Ki), L1 = 100100 and R1 = 111000 .

Round 2 (i = 1)

1. L1 = 100100 and R1 = 111000 ;
K2 = 10011110.

2. E(R1) = 11010100.

3. E(R1) XOR K1 = 11010100 XOR 10011110= 01001010.

4. S1(0100) = 011; S2(1010) = 000;   
f(R1,K2) = 011000

5. f(R1,K2) XOR L1 = 0110000 XOR 100100 = 111100.

6. Now using the formulas Li = Ri-1 and Ri = Li-1 f (Ri-1, Ki), L2 =111000 and R2 = 111100

So encrypted message, R2 L2 = 111100111000

Decryption

Round 1(i = 0)

1. L0= 111100 and R0= 111000 ;
K2 = 10011110.

2. E(R0) = 11010100.

3. E(R0) XOR K1 = 11010100 XOR 10011110= 01001010.

4. S1(0100) = 011; S2(1010) = 000;
f(R0,K2) = 011000

5. f(R0,K2) XOR L0 = 011000 XOR 111100 = 100100

6. Now using the formulas Li = Ri-1 and Ri = Li-1 f (Ri-1, Kn-i), L1 = 111000 and R1 = 100100.

Round 2 (i = 1)

1. L1 = 111000 and R1 = 100100;
K1 = 01001111.

2. E(R1) = 10101000.

3. E(R1) XOR K1 = 10101000 XOR 01001111= 11100111.

4. S1(1110) = 101; S2(0111) = 010;
f(R1,K1) = 101010

5. f(R1,K1) XOR L1 = 101010 XOR 111000 = 010010.

6. Using the formulas Li = Ri-1 and Ri = Li-1 f (Ri-1, Kn-i), L2 = 100100 and R2 = 010010

So decrypted message, R2 L2 = 010010100100 ,

which is same as the original plaintext message.

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