1. Name one issue with asymmetric key cryptosystems.

   - Encryption/decryption much slower (higher computational cost)
     than symmetric cryptosystems.

   - When used for signing, both encrypted message and original message
     required for signature verification.

2. In the ACS Code of Ethics, which among the following has the highest
   priority?

   Confidentiality   Integrity   Competence   Promoting information technology
                     ---------

3. When decrypting a signed message using RSA, which key is used?

   sender's public key   sender's private key   receiver's public key   receiver's private key
   -------------------


4. An example of a symmetric key algorithm is:

   RSA   AES   El Gamal
         ---

5. How many bits are in a DES key?

   64   56   128
        --

6. Why are public keys normally used to encrypt session keys?

   To overcome the key distribution problem associated with the
   distribution of symmetric keys (session keys are normally symmetric
   keys). This approach allows a sender to securely transmit a session
   key encrypted with the receiver's public key, to the receiver.

7. Encryption using AES provides the following service:

   confidentiality   integrity   authentication
   ---------------

8. How will a receiver verify a message signed using RSA, when a hash function
   is used in generating the signature?

   When a hash function is used to generated the signature, the receiver
   will (should) receive a signed hash plus the original message. The
   receiver will use the sender's public key to decrypt the signed hash,
   thus obtaining the actual hash, say H(m). The receiver will then
   run the same hash algorithm that the sender used over the original
   message to get its hash, say H(m)'. If the two hashes are the same
   (H(m) equals H(m)'), then the signature is verified.