1. Briefly describe the criteria and properties for evaluating and constructing modes of operation for block ciphers

2. With the aid of a diagram, explain the mechanism of operation of the CBC encryption and decryption process.

3. With the aid of a diagram, demonstrate CBCs self-healing property.

4. Compare and contrast ECB, CBC and CTR/CM with regard to the possibility (or impossibility) to parallelize the encryption and decryption process. You must provide explanation to back up your answer.

5. Describe the advantages of the counter mode (CM) relative to the other modes of operation.

6. What problems might the counter mode face if the counter used is not a nonce?

7. Under what circumstances would it be advisable or inadvisable to use the ECB mode of operation?