T215B: Communication and information
technologies
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Tutor-Marked
Assignment
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Total
Marks: 100
Part 1: Cryptography (50 Marks)
As an AOU student,
suppose that you were attending a T215B discussion session during which many
questions about data encryption in general were raised as well as other
questions about a well-known cryptographic algorithm called RSA in particular.
Those can be summarized as follows:
·
Encryption: (6
Marks)
§
What is encryption?
§
What is it used for?
§
What are its advantages and
disadvantages?
·
Symmetric key cryptography: (6
Marks)
§
What is symmetric key
cryptography?
§
What are its applications?
§
What are its advantages and
disadvantages?
·
Asymmetric and public key
cryptography: (6
Marks)
§
What is asymmetric key cryptography
and why it is usually called public key cryptography?
§
What are its applications?
§
What are its advantages and
disadvantages?
·
Modular arithmetic: (8
Marks)
§
What is Modular arithmetic in
general?
§
What are Modular addition,
multiplication and exponentiation? Examples?
·
Factorizing large prime
numbers: (6
Marks)
§
What is a prime number?
§
How large prime numbers can be
useful to cryptography?
·
RSA
keys generation technique: (7
Marks)
§
What is RSA algorithm?
§
How to create the RSA public
and private keys?
Since the students were highly interested and
motivated to understand what encryption and RSA algorithm are about, the mentor
of this discussion session asked you as an active participant to elaborate
reliable answers to these raised questions by editing a medium length report
(1000-1200 words). He also offered you the opportunity to present this report
to all your classmates during the next discussion session.
In this question of the TMA, you are supposed to
edit the requested report taking into consideration the following points:
ü Your report should be between 1000 and 1200 words in length. Under-length
and over-length reports will be penalized. (2
Marks)
ü Your report must provide reliable answers for all the above questions.
(Check the
marks awarded for each concern)
ü
You might need to form some idea of how many
words you need to give to each concern.
(Check the
marks awarded for each concern)
ü
Your report should include titles, subtitles and at least two figures
and/or tables. Do not forget to include captions and to use cross-referencing. (3 Marks)
ü
Ensure that your report meets the objectives,
has an appropriate structure and style, and that its technical level is
appropriate for the audience, purpose and medium. For more details, you can
refer to the T215 textbooks (Block 1 – Part 7; Block 2 – Part 7; Block 3; Block
4 – Part 8). (3
Marks)
ü
Your report should be based on reliable
resources (i.e. journal articles, technical reports, conference papers,
international textbooks) and you should provide a reference list at the end of
your report. The references should be in a standard form. (3 Marks)
ü
You are advised to remind yourself of the
issues concerning plagiarism.
Part 2: Securing a report (50 Marks)
The Arab Open University – AOU
– is a multinational university with several branches around the Arab World.
Recently, it has been earning itself a reputation for its success in
credibility and high educational issues. Suppose that you are working as a
financial expert in one of the AOU’s Branches and that you were asked to edit a
highly confidential report about the financial activities at your Branch. After
two weeks of hard work, you finalized the report and now it is ready to be
delivered.
However, as per an urgent
request from the AOU headquarters, your Branch Director was invited to attend
an urgent meeting outside the country to discuss your Branch’s financial
activities and he hence asked you to send him by email a soft-copy of the
report you prepared taking into consideration the sensibility of the
information it contains.
In this question of your TMA, you are supposed to investigate
three different encryption techniques and to deduce which one of them provides
for your report the highest level of confidentiality.
2.A. Privacy, surveillance and security threats
Based on what you learned in T215B about “Privacy and
Surveillance”, discuss two different kinds of threats that might confront your
confidential report when it is sent by email to your Branch director. (Respect a maximum word count of 200
words). (6
Marks)
In all the
following questions and for simplicity reasons, suppose that your report
contains the following sentence: “High Profit”.
2.B. Caesar Cipher
a) In no more than 150 words explain the Caesar encryption technique. (4 Marks)
b) Use Caesar algorithm to encrypt the content of your report with a key K=14.
(4 Marks)
c) Does the
Caesar cipher ensure a high level of security? What are its drawbacks? Explain.
(2 Marks)
d) What is the
decryption key your director should use to decrypt the encrypted report? (2
Marks)
2.C. Caesar Cipher with Diagraph Coding
a) In no more
than 150 words explain the main idea of Diagraph coding. Does its
implementation in a Caesar Cipher algorithm increase the security level of the
ciphertext? Why/Why not? (5 Marks)
b) Use Caesar Cipher with Diagraph Coding to encrypt the content of your report with a key K=321. (8 Marks)
2.D. Vigenère Cipher
a) In no more than 150 words explain the main idea of the Vigenère Cipher. Does it ensure a high level of security? What can make it an unbreakable cipher? Illustrate. (6 Marks)
b) Use the keyword “zratxhuekf” to encrypt the content of your report using the Vigenère Cipher. (5 Marks)
c) What is the
keyword that might be used to decrypt the ciphertext? (5 Marks)
2.E. Recommendations
Which of the previously studied ciphers
would you recommend using to encrypt your report before sending it to your
Director? Give strong arguments for you recommendation. (3
Marks)
Notes for Question 2:
ü
In questions 2.B.b, 2.C.b and 2.D.b, you are requested
to illustrate, step by step, how you have applied each encryption technique.
ü
You can use external reliable resource(s) to elaborate your answers but
ensure that you provide its (their) reference(s) at the end of your
answer. The reference(s) should be in a standard form.
ü
You are advised to remind yourself of the
issues concerning plagiarism.
***************************
End of
TMA
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Q−8: [5×1
Marks] Let P(t) be the
population (in millions) of a certain city t years after 1950, and suppose
that P(t) satisfies the differential equation P′(t)
= 0.017 P(t), P(0)= 2560
a)
Find the formula for P(t).
b)
What was the initial population
(the population in 1950) ?
c)
What is the growth
constant?
d)
What was the population
in 1960?
e)
Estimate the population
in the year 2020.
