Explanation: PKl is the administrative infrastructure for digital certificates and encryption key pairs. The qualities of an acceptable digital signature are: it is unique to the person using it; it is capable of verification; it is under the sole control of the person using it; and it is linked to data in such a manner that if data are changed, the digital signature is invalidated. PKl meets these tests. The Data Encryption Standard (DES) is the most common private key cryptographic system. DES does not address nonrepudiation. A
MAC is a cryptographic value calculated by passing an entire message through a cipher system. The sender attaches the MAC before transmission and the receiver recalculates the MAC and compares it to the sent MAC. If the two MACs are not equal, this indicates that the message has been altered during transmission; it has nothing to do with nonrepudiation. A PIN is a type of password, a secret number assigned to an individual that, in conjunction with some other means of identification, serves to verify the authenticity of the individual.