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.