18.4.3. Concrete Mathematical Algorithm

Try these first

1. 1.

   What is symmetric key encryption?

   Hint

   Think about how locks and keys work.

2. 2.

   What is ciphertext?

   Hint

   What do you call the message after it has been scrambled?

3. 3.

   What does symmetric key encryption use?

   • Two different keys
   • One shared key
   • Public keys

   Hint

   Think about the analogy of a shared lock and key.

4. 4.

   True or False: The Diffie-Hellman protocol allows the exchange of symmetric keys over a public channel.

   • True
   • False

   Hint

   Reflect on how they derive the key without revealing it.

5. 5.

   If Sita chose a random integer of 5, and Ram chose 7, explain the process in deriving their shared key using a cyclic group of prime number 11.

   Hint

   Use the properties of the cyclic group to illustrate how they derive the common key.

6. 6.

   Critically evaluate the security risks associated with symmetric key encryption when keys are poorly managed.

   Hint

   Consider what could happen if someone intercepts or gains access to the key.