Design a scheme by which a credit card user can authenticate to a credit card processing company so that a merchant could be confident the user was the rightful owner of the credit card. Your scheme should have three aspects: first, for a face-to-face transaction, for example, a purchase in a store; second, for a voice transaction, for example, a purchase by telephone; third, for an electronic transaction, for example, a purchase on the Internet. Describe the difficulty for the user, for example, your scheme might require the user to carry a token that might be inconvenient to carry. Describe the delay factor, if any, in the merchants seeking authentication. This question is focused on providing assurance to the merchant. Does it also protect the user or the credit card processor? Why or why not?

(Computer Security II)