Task 1
Which of the following are desirable properties of secure communication?
a) End-point authentication
b) Operational security
c) Confidentiality
d) Public key cryptography
e) Message integrity
Task 2
Which of the following statement(s) is/are correct?
a) Message confidentiality is the property that the identity of the sender can be
confirmed to be who or what they claim to be.
b) Message integrity is the property that the receiver can detect whether the message sent
(whether encrypted or not) was altered in transit.
c) A cryptographic hash function has a property that states that it is computationally
infeasible to find two messages which have the same hash function.
d) A message authentication code (MAC) always uses a shared key to strengthen
message integrity.
Task 3
Let’s say we have a group of 15 people. How many secret keys are necessary for allowing
each member to communicate confidentially with each of the other members separately,
when using symmetric key cryptography?
a) 15
b) 29
c) 105
d) 210
e) 225
Task 4
The scenario is the same as in the question above, but with public key cryptography. How
many secret keys are necessary now?
a) 15
b) 29
c) 105
d) 210
e) 225
Task 5
Considering information transmission between Alice and Bob through a network with the
existence of an intruder (Trudy). Which of the following statement(s) is/are correct regarding
what kinds of information the intruder can access and what kinds of action can be taken.
a) Deletion of message or message content
b) Recording data messages on the channel
c) Sniffing and recording control messages on the channel
d) Modifying or insertion of messages
Task 6
The figure below illustrates video transmission from a server to a client. The server transmits
the first video block at t0
, the second block at t0+ Δ, the third block at t0+ 2Δ, and so on. Once
the client begins play out, each block should be played out Δ time units after the previous
block. Suppose that the client begins play out at t1 + Δ. Among the first 7 video blocks, which
of them will have arrived at the client in time for their play out?
a) Block 1
b) Block 2
c) Block 3
d) Block 4
e) Block 5
f) Block 6
g) Block 7
Task 7
Suppose now that the client begins play out at t1 + 2Δ. Among the first 7 video blocks, which
of them will have arrived at the client in time for their play out?
a) Block 1
b) Block 2
c) Block 3
d) Block 4
e) Block 5
f) Block 6
g) Block 7
Task 8
HTTP streaming is more popular than UDP streaming in video streaming applications. Which
of the following statements(s) can explain this?
a) UDP is connection-oriented, and the initial handshake can cause delays.
b) UDP can fail to provide continuous playout, because of unpredictable amount of
available bandwidth.
c) Many firewalls are often configured to block most UDP traffic but to allow most
HTTP traffic.