CSEC Coursework

CSEC Coursework, 2019/2020 Page 1

School of Computing

Module Coordinator

Other lecturers

Dr Benjamin Aziz

Date Issued 3rd February 2020

Code CSEC / U30606

Title CSEC Coursework

Schedule and Deliverables

Item Value Format Deadline Lat deadline

Ecf deadline

Report Total mark = 100

Report overall

weight = 40%

A single .pdf file submitted

through Moodle containing

your answer to all tasks.

You may use the template

provided for your answers

2020-05-06 12:00

[GMT]

2020-06-05 12:00

[GMT]

Notes and Advice

• The Extenuating Circumstances procedure is there to support you if you have had any

circumstances (problems) that have been serious or significant enough to prevent you from

attending, completing or submitting an assessment on time.

• ASDAC are available to any students who disclose a disability or require additional support

for their academic studies with a good set of resources on the ASDAC moodle site

• The University takes plagiarism seriously. Please ensure you adhere to the plagiarism

guidelines.

• Any material included in your coursework should be fully cited and referenced in APA format

(sixth edition). Detailed advice on referencing is available from http://referencing.port.ac.uk/

• Any material submitted that does not meet format or submission guidelines, or falls outside of

the submission deadline could be subject to a cap on your overall result or disqualification

entirely.

• If you need additional assistance, you can ask your personal tutor, learning support

Ana.baker@port.ac.uk and xia.han@port.ac.uk or your lecturers.

CSEC Coursework, 2019/2020 Page 2

Coursework-related Instructions

Please read the following instructions carefully.

Answer ALL of the following EIGHT questions. Each question carries its own mark and the total

coursework mark is 100. The mark for each question and your coursework is calculated as follows:

- If you choose the correct option among the multiple choices for a question, you will be

awarded a mark “up to” the maximum of the positive mark allocated for that question. Your

awarded mark for the question will depend on the explanation you provide as to why you

made the (correct) choice. If you provide no explanation whatsoever, and you chose the

correct answer, you will be awarded ONE mark only for that question.

- If you choose any of the wrong answers in a question, the negative mark assigned to that

question will be added to your overall coursework mark, resulting in the overall mark being

reduced.

- If you do not answer a question, you will be awarded ZERO marks for that question.

- If your coursework’s total mark is negative, it will be rounded up to ZERO.

- Always choose only one answer per question. If you choose more than one answer in a

single question, you will be awarded ZERO for that question.

CSEC Coursework, 2019/2020 Page 3

Question 1 (Positive Mark: 15, Negative Mark: -15)

Cryptographic Data Objects

B has just received the following message, which represents a cryptographic data object:

{(

{(KPbB)KPrS mod KPbS}K1,

{|(NB, NA, {{({K2}KPbB, NS)}(G1)KPrA mod NA}K1, {|{({G3}(KPbA)KPrS mod KPbS, G2)}K1|}KPrB)|}KPrA

)}KBS

The following explains various terms in this object and some of the abbreviations used:

• {M}K represents the encryption of some message/data M using the key K

• {|M|}K represents the digital signing of some message/data M using the key K

• NX represents a nonce (i.e. a fresh and possibly random number used once only) generated

by X

• KpbX represents the public part of the key pair presumably owned by X

• KprX represents the private part of the key pair presumably owned by X

• KAB represents a symmetric key shared between A and B

• K (or K1, K2, K3 etc.) represents some arbitrary key with no assumptions about its scope

• M represents some alphanumeric/textual message with no assumptions

• G1, G2, G3 etc. are prime numbers

which of the following sets of keys, nonces, numbers, and alphanumeric/textual messages “best”

represents B’s knowledge, after B applies any number of possible cryptographic operations to the

object above, and assuming that B already has access to key K1 and the public key of any agent:

a) KBS , G2 , KPrB

b) {(KPbB)KPrS mod KPbS , G2 , KBS , KPrB , {(KPbB)KPrS mod KPbS}K1, NA , NB

c) NA , NB

d) NA , NB , KBS , KPrB

e) {(KPbB)KPrS mod KPbS}K1 , {|(NB, NA, {{({K2}KPbB, NS)}(G1)KPrA mod NA}K1, {|{({G3}(KPbA)KPrS mod

KPbS, G2)}K1|}KPrB)|}KPrA , NA , NB , KBS , KPrB , {(KPbB)KPrS mod KPbS

f) G2 , NA , NB , G1 , KBS , KPrB

g) (KPbB)KPrS mod KPbS , NA , NB , G2 , KBS , KPrB

h) (KPbB)KPrS mod KPbS , (G1)KPrA mod NA , NA, NB , G2 , KBS , KPrB

i) (KPbB)KPrS mod KPbS , G3 , G2 , KBS , KPrB

j) (KPbB)KPrS mod KPbS , NA , NB , G2 , KBS , KPrB , G3 , (KPbA)KPrS mod KPbS

k) NB

Explain your answer below:

CSEC Coursework, 2019/2020 Page 4

Question 2 (Positive Mark: 15, Negative Mark: -10)

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:

CSEC Coursework, 2019/2020 Page 5

Question 3 (Positive Mark: 10, Negative Mark: -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:

CSEC Coursework, 2019/2020 Page 6

Question 4 (Positive Mark: 10, Negative Mark: -2)

Forwards 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 below:

CSEC Coursework, 2019/2020 Page 7

Question 5 (Positive Mark: 10, Negative Mark: -6)

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:

CSEC Coursework, 2019/2020 Page 8

Question 6 (Positive Mark: 10, Negative Mark: -10)

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

Explain your answer below:

CSEC Coursework, 2019/2020 Page 9

Question 7 (Positive Mark: 15, Negative Mark: -10)

Access Control Models and Policies

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)

Explain your answer below:

CSEC Coursework, 2019/2020 Page 10

Question 8 (Positive Mark: 15, Negative Mark: -7)

Security Datasets and Metrics

Considering the Cyber security open datasets provided by the Los Alamos National laboratory

(https://csr.lanl.gov/data/). Choose which one of the datasets below, would be most suitable to the

definition of a metric for measuring the probability of the leakage of data from computers. To help

you consider which dataset is best suited, you can imagine the scenario where you use the public

laptops provided in the lockers in the Future Technology Centre (FTC) floors 1 or 2 during your

tutorial hour for this module.

a) dns.txt.gz

b) redteam.txt.gz

c) User-Computer Authentication Associations in Time

d) Unified Host and Network Dataset

e) auth.txt.gz

f) proc.txt.gz

g) flows.txt.gz

Explain your answer below: