Authentication Protocols - IT Assignment Help

Assignment Task:

Task:

Question 2 Authentication Protocols
Consider the following 4-message protocol:
1. A → S: (B, {(A, K1)}KpbS)
2. S → B: A
3. B → S: (A, {(B, K2)}KpbS)
4. S → A: (B, {K2}K1)
Which of the following statements is true, at the end of the protocol, and with regards to the purpose of the protocol:
a) Both A and B establish a session key K2, and B is sure of A’s identity
b) Both A and B establish a session key K1, and B is sure of A’s identity
c) Both A and B establish a session key K1, and A is sure of B’s identity
d) Both A and B establish a session key K1, and both B and A are sure of each other’s identity
e) Both A and B establish a session key K2, and A is sure of B’s identity
f) Both A and B establish a session key K1
g) Both A and B establish a session key K2
h) Both A and B authenticate each other by knowing each other’s identities
i) A ends up knowing B’s identity
j) B ends up knowing A’s identity
k) None of the above
l) All of the above
Explain your answer below
Question 3 Non-Repudiation and Anonymity Protocols
For the Zhou-Gollman non-repudiation protocol discussed in the lecture on “Non-Repudiation and Anonymity Protocols”

which one of the following statements is false:
a) At time point 4, both A and B can produce evidence to prove that they received K
b) At time point 2, both A and B can produce evidence to prove that they received a signed message from the other party

c) At time point 0, S cannot prove anything
d) At time point 3, B cannot produce evidence to prove that A has access to key K
e) At time point 1, A can prove that B is alive
f) At time point 4, S can prove that A is alive
g) At time point 3, S can produce evidence that that A has access to key K
h) At time point 0, A is not alive
i) At time point 2, A can produce evidence to prove that B is alive
j) At time point 4, the protocol terminates
Explain your answer below
Question 4 Forward Secrecy Protocols
Consider the following 4-message protocol:
1. A → S: (B, {(A, K1)}KpbS)
2. S → B: A
3. B → S: (A, {(B, K2)}KpbS)
4. S → A: (B, {K2}K1)
Assume three runs of the above protocol, that we call P1, P2 and P3. If after completion of run P3, K1 is compromised, i.e. it is leaked to some external intruder, how would this impact the forward secrecy property of K2 for all the three runs of the protocol P1, P2 and P3? Choose the right answer:
a) Compromising K1 in P3 compromises every other key in all of the three runs of the protocol
b) The secrecy of P3.K2 is not compromised, and therefore P2.K2 and P1.K2 would remain secret
c) Compromising K1 in P3 compromises P3.K2, and therefore, every other previous version of K1 and K2 are also compromised
d) The secrecy of P3.K2 is compromised, but P2.K2 and P1.K2 would remain secret since K1 is refreshed after each run, therefore P3.K1 is different from P2.K1 and is different from P1.K1
e) Even though K1 is compromised in P3, K2 is not compromised in any of the three runs
Explain your answer
Question 5 Attacks on Security Protocols
Consider the following 4-message protocol:
1. A → S: (B, {(A, K1)}KpbS)
2. S → B: A
3. B → S: (A, {(B, K2)}KpbS)
4. S → A: (B, {K2}K1)
And the following attack trace:
1. I(A) → S: (B, {(A, K)}KpbS)
2. S → B: A
3. B → S: (A, {(B, K2)}KpbS)
4. S → I(A): (B, {K2}K)

Which one of these changes to the protocol messages would fix the attack trace above, such as the attack then becomes impossible:
a) 3. B → S: (A, {(B, {K2}KpbA)}KpbS)
b) 4. S → A: (B, {K2, A}K1)
c) 2. S → B: {A}KpbB
d) 2. S → B: B
e) 3. B → S: (A, {(B, {K2}KprS)}KpbS)
f) 1. A → S: {(B, A, K1)}KpbS
g) 1. A → S: (A, {(B, K1)}KpbS)
h) 4. S → A: (B, {K1}K2)
i) 4. S → A: (A, B, {K2}K1)
j) 2. S → B: A, B
Explain your answer below
Question 6 Mutation and Type-Flaw Attacks
Consider the following 4-message protocol between A and B, where (N+1) represents the increment of N:
1. A → B: (A, {NA}KAB)
2. B → A: {(NA+1, NB)}KAB
3. A → B: {NB+1}KAB
4. B → A: {(K’AB, NA)}KAB
Which of the following mutations to messages of the protocol above, would constitute a harmful attack:
a) 1. A → B: (C, {NA}KAB)
b) 1. A → B: ({NA}KAB, A)
c) 4. B → A: {(KAB, NA)}KAB
d) 4. B → A: {(K’AB, NB+1)}KAB
e) 3. A → B: {NB+1}KpbB
f) 2. B → A: {(NA+1, NA)}KAB

Question 7 Access Control Models
Assume a network that consists of a set of nodes, {a, b, c, d, e, f, g, h, j, k, l, x, z}. These nodes have the following partial order relation on them:
{(b≤a), (f≤e), (z≤l), (z≤x), (l≤g), (c≤b), (g≤k), (e≤d), (g≤h), (k≤j), (g≤e), (e≤c), (d≤b), (x≤e)}
Furthermore, assume that a BLP policy is being enforced in the above network. Now assume that at some stage, node z becomes infected with a virus. Which one of the following sets of actions would also lead to infecting node a, assuming that viruses propagate through a network using the read and write commands. A virus would propagate from one node to another either because the second node read from the first one, or because the first node wrote to the second one. All read and write commands are subject to the policy being enforced and no read or write operation is possible in the absence of an order (either direct or indirect) between two nodes:

a) (l read from z), (l write to g), (g read from l), (g read from e), (e write to c), (c write to b), (a read from b)
b) (z read from l), (a read from l)
c) (z write to x), (x write to e), (a read from e)
d) (z write to c), (b write to c), (a read from b)
e) (z write to g), (g write to h), (b read from h), (b write to a)
f) (x read from z), (x write to e), (e write to d), (a write to d)
g) (z write to g), (j read from g), (j write to d), (d write to b), (a read from b)
h) (z write to l), (l write to g), (g write to c), (c write to d), (d write to b), (b write to a)
i) (a write to z)
j) (f read from z), (a read from f)

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