Department of Computing COMP347 Advanced Computer Networks Assignment 2, Semester 2 2019 Due: Tuesday 29th October, 2019, 5 pm Marks: 60 Value: 15% Topics TCP Security Submission Submit on line via Turnitin link on COMP347 iLearn page. Please do not double space lines. Assignments will be marked and returned online. There are no hardcopy submissions for written assignments. 1.Security and Applications (20 marks) Authentication has long been a problem for transactions. How do you know if someone presenting a card really is the owner of that card? Simple methods include matching a signature to a previously signed one on the back or entering a PIN. Now with PayWave, only authentication by possession (of the card) is required.
Currently, there are a number of initiatives to use mobile devices for the functionality of payment. This raises the question of how safe are the devices and what mechanisms are built in to prevent fraud. A number of platform vendors have introduced electronic card payments to their devices. For example Apple introduced ApplePay in iPhone and Apple Watch. With reference to the techniques in the security lectures, examine how various vendors approach secure payments. Is it easy to use for legitimate users while difficult to crack for attackers? Does it provide confidentiality, integrity, authentication, anti-replay, and non-repudiation? In what ways might these transactions be compromised and how are they counteracted?
You should start with a general description of Apple Pay and another (Android- based) service, an overview of how it works, and what encryption is used. Where is encryption applied? Examine the authentication functions. What protocols are used? Then evaluate it with reference to the previous paragraph. How do the different vendor’s offerings compare? Where are they the same or similar, and how do they differ?
Here are a few web links you can start with, but you should also find your own: GooglePay API Google Android PaymentsClient API ApplePay API AppleInsider article on PayPal’s doubts about ApplePay’s security AppleInsider’s article on the ApplePay and NFC patent PayPal’s Braintree Blog on ApplePay Some background to iOS security although it predates Apple Pay: Apple iOS Security Guide 2. TCP (40 marks) Host A and B are communicating over a TCP connection, and Host B has already received from A all bytes up to byte 126. Suppose Host A then sends two segments to Host B back-to-back. The first and second segments contain 80 and 40 bytes of data, respectively. In the first segment, the sequence number is 127, the source port number is 3024, and the destination port number is 80. Host B sends an acknowledgement whenever it receives a segment from Host A. a. [5 marks] In the second segment sent from Host A to B, what are the sequence number, source port number, and destination port number? b. [5 marks] If the first segment arrives before the second segment, in the acknowledgement of the first arriving segment, what is the acknowledgement number, the source port number, and the destination port number? c. [5 marks] If the second segment arrives before the first segment, in the acknowledgement of the first arriving segment, what is the acknowledgement number? d. [10 marks] Suppose the two segments sent by A arrive in order at B. B sends acknowledgements for both segments, but the first acknowledgement is lost and the second acknowledgement arrives after the first timeout interval. Draw a timing diagram showing these segments and all other segments and acknowledgements sent (you can assume no other segment loss). For each segment in your diagram, provide the sequence number and the number of bytes of data; for each acknowledgement that you add, show the acknowledgement number. e. [5 marks] As we have seen, the Internet layer of TCP/IP has two protocols – IPv4 and IPv6. The transport layer provides two main protocols TCP and UDP (along with some special-purpose, minor protocols). But these are for very different reasons. Why are the Internet and Transport layers very different in providing two protocols? f. [5 marks] Since UDP does very little that is different from IP, why do we even have a transport layer such as UDP? g. [5 marks] Describe how DDoS attacks may be mounted against TCP and UDP services. In what way will being connection oriented be different for TCP and UDP? Assessment For all questions in this assignment not only content but also presentation will affect your mark. You will lose marks (and not necessarily only a small portion) if there are problems with the presentation, particularly with clarity. This means that your answers to each question should be a coherent statement and that the spelling and grammar of your submission will be taken into account in assessing its presentation. For full marks, your answers should all be clear, coherent and correct. The standards of marking described in the unit outline L.O. 1-4 will be applied to this assignment as relevant to the assignment topics. In addition, the following particular standards will be applied in marking this assignment: Correctness of approach Incorrect answers with the correct logic or approach will receive no more than a pass for the individual question. Correct answers within correct logic or approach will receive no more than pass for the individual question. Incorrect answers with no explanation of the approach taken or with the incorrect approach will receive a fail grade for the individual question. The questions will be marked individually, the marks totalled, and a final grade assigned that is no more than indicated by the total marks, and no more than allowed by the standards specified above and in the unit outline. Clarity Multi-paragraph answers should be structured into sections and subsections with appropriate headings and subheadings. Ambiguous or poorly worded answers will receive a grade no more than a pass for the individual question. Minor issues of clarity will receive a grade no more than credit for the individual question. Spelling and grammar Assignment submissions with more than 4 spelling or grammatical errors will not achieve a grade higher than distinction; submissions with more than 8 such errors will not achieve a grade higher than credit. Bibliography Guidelines In your bibliography be careful to identify the source of all material that you use and to clearly identify any quotations that you make. (See the section on plagiarism, below.) Here is an example of a quotation using the Harvard method of citation:
“In this assignment, you must be particularly careful to avoid plagiarizing your articles or any other sources of information.” (Shankaran, 2005) And here is an example of a bibliography entry: Shankaran, R. “Comp247 Assignment 2” 2005. [available online http:// www.comp.mq.edu.au/units/comp247/assigns/ass2.pdf; accessed May 2005]. Any quotations that are not properly identified will be considered as plagiarism and will attract a penalty. For more information on how to write bibliographies, you can find resources on the Internet such as How to Write a Bibliography (an introduction) or Bibliography Guides (a detailed description of the APA style). However, we do not require a strict adherence to any particular bibliography style provided that you include the key information such as authors, article title, date of publication and title of publication, and provided that your citations are clear. Originality All material must be in your own work and expressed in your own words. Plagiarism You should be well aware by now of the University’s plagiarism policy. In this assignment, you must be particularly careful to avoid plagiarising your articles or any other sources of information. If you wish to directly quote any portion of another document, you must enclose your quotation in quot
ation marks and immediately following the quotation you must identify your source. It is important that you do not attempt to write your essay by pasting together pieces of text that you find on the Internet. You need to write your own words and phrases that express your own ideas. You must also list all sources used in your answer/essay in a bibliography at the end of the answer/essay.
