List the four problems addressed by cryptography, and give a real-world example of each.

What will be an ideal response?

The four problems that concern cryptography include privacy, integrity, authenti-
cation and nonrepudiation. An example of the privacy issue is the passing of credit
card information for online purchases. Integrity would deal with ensuring that this
information is not altered during transmission. The buyers would be concerned with the authenticity of the site that their credit card information is being sent to, ensuring that impostors were not stealing information. Nonrepudiation deals with making sure that, once the transaction has completed, it cannot be disputed.