1. What are the two main advantages and two main limitations of public key encryption compared with symmetric encryption?

  2. Draw a diagram to show how a single message can be both encrypted and authenticated using public key encryption

  3. Many communications systems use a combination of public key encryption and symmetric encryption. Why is this the case, and how does it work?

  4. Explain why the security of RSA depends on the difficulty of factoring large numbers

  5. Using the following key generation parameter values chosen for an RSA system: p = 17, q = 7, e = 13 Find the values of the private key components, d and n. Encrypt the message which is 11100001 in binary using this RSA system.

  6. What is the purpose of the Diffie-Hellmann public key technique? Briefly describe it.

  7. Prove that Diffie-Hellman works i.e. that the secret keys calculated by both sides of the communication are identical.

  8. In what situation does Elliptic Curve Cryptography perform better than RSA?

  9. Discuss the significance of key size in cryptography? In your answer, comment on both symmetric and public key encryption.