Enhancing Cyber Security of Networked Control Systems using Encryption

Computer Science
Cyber Security
As per Kogiso & Fujita (2015) the idea if controller encryption can be used to enhance the cyber
security of networked control systems. Kim et al (2016) has shown that the security can be
enhanced by protecting the signals from the sensor to the controller and controller to actuator.
This can be done using encryption.
Plaintex
t
Ciphertext Plaintex
t
Ciphertext
0 a 8 e
1 c 9 d
2 f a 0
3 6 b 7
4 3 c 5
5 8 d b
6 4 e 9
7 2 f 1
3. (3 pts)
a. Encrypt the 4-block message cafe using this cipher for each digit individually.
Solution:
Encryption – café = 5019
b. Decrypt the message 199b using this cipher.
Solution:
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Decryption – 199b = feed
c. Why is it insecure to use a block cipher in this way? Do not critique the block cipher
itself, but only how it is used.
Solution:
This is insecure because in case the substitution cipher table gets leaked, then all the
encrypted messages can be easily decrypted.
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4. (6 pts) For this question, you will perform encryption and decryption using the same
block cipher given above, but in CBC mode. Recall that you can convert hexadecimal
digits to binary to do the XOR operation.
i. Encrypt the 4-block message cafe using the above blockcipher in CBC mode with an
IV of 6 (0110in binary).
Solution:
In this case we will first Exor the Inititalization vector ( IV ) with the plain text. Then,
we apply the key and go to next step.
ii. Decrypt the message db70 using the above cipher in CBC mode with an IV of 6.
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