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CSCI968 Advanced Network
Security Summer 2024
Assignment 3 (15 Marks)
Due: 15 Aug 2024 23:30
1. Consider the following certificate structures.
a) What could happen if the “Lifetime information” was not signed by CA. Justify your
answer. (2 marks)
b) What could happen if the “Name of the user” was not signed by CA. Justify your answer.
(1 marks)
2. In a mobile roaming system, there are three entities: a mobile user U, its home server H, and
a foreign server V. The mobile user U, who is subscribed to the home server H, is currently in
a foreign network administered by the foreign server V. There is a direct link between U and
V, and another direct link between V and H. However, there is no direct link between U and
H. In order to obtain the services provided by V, U must be authenticated by V (with the help
from H).
Suppose that the mobile user U shares a symmetric-key K
UH
with its home server H. The home
server H and the foreign server V also have public keys PK
H
and PK
V
that are certified by a
trusted CA (H and V both have certificates). You task is to design a secure authentication and
key establishment protocol which can satisfy the following security requirements.
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