Section B
1. Assume that a client A and server B share a symmetric key K and have securely distributed
their public keys K+A and K+B. Suppose client A wants to send a message to server B
containing the name N, ID number, and a request R for Bob. Denote the message as C =
{N, ID, R}. Design the cryptographic messages that client must send to meet the security
requirements below:
(a) Using the symmetric key, design a message that enables server B to verify that the
message’s integrity has not been violated and that it is from client A.
(b) Using the symmetric key, design a message that protects the confidentiality of the
request only and ensures that server B can verify the message’s integrity and source.
(c) Using public key cryptography, design a message that enables sever B to verify that
the message’s integrity has not been violated and that it is from client A.
(d) Using public key cryptography, design a message that protects the confidentiality of
the request only and ensures that server B can verify the message’s integrity and
source.
