1.1. (10 pts) Visit the class discussion group in the Blackboard. Post a message with your full name as the subject line. In your post, briefly introduce yourself, including your full name, your major, and one or two items that you most desire to learn in this class. Throughout this class, you shall regularly participate at the discussion group to find recent announcements, reminders, and discussions.

1.2. Cyber attacks: Explain what each of the following attacks is. Cite your source(s).

Note: Not all information published on the web are correct. Discern the validity of the information you use by, for example, comparing them with what you have learned from the textbooks and the class discussions.

a. (10 pts) Replay attacks

b. (10 pts) Man-in-the-middle attacks

1.3. In an online banking application, the customer may transfer fund between the saving account and the checking account.

a. (10 pts) Explain what data integrity means in this context.

b. (10 pts) Explain what origin integrity means in this context.

c. (10 pts) Explain what availability means in this context.

d. (10 pts) Explain what confidentiality means in this context.

e. (10 pts) Explain what non-repudiability means in this context.

1.4. Digital Signature Algorithms

a. (10 pts) Digital Signature is a cryptographic mechanism that that may be implemented in a computer system to provide three security services (i.e., data integrity, signer origin integrity, and signer non-repudiability). Explain how each of those three security services is provided by the Digital Signature.

b. (10 pts) Are there any drawbacks with the Digital Signature? Under what circumstances it may not be effective to implement Digital Signatures?

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Lab 2

Total: 100 points

1. (10 pts) Explain the relationship between replay attacks and Denial of Service (DoS) attacks. Hint: How would the hacker use replay attacks to cause Denial of Service?

2. (10 pts) Explain the differences between replay attacks and man-in-the-middle attacks.

3. (10 pts) Explain the relationship between Polluted DNS attacks and man-in-the-middle attacks. Hint: How would polluted DNS be used by the hacker to launch a main-in-the-middle attack?

4. (10 pts) Suppose entity A intends to send a message (m) to entity B. The desirable security services are confidentiality, data integrity, and origin integrity. Explain what each of those security services mean in this context.

5. (10 pts) (continued from above) Explain how each of those services may be provided (by what mechanisms).

6. Hands-on lab

6.1. To prepare your computer for the remaining hands-on labs, set up your computer according to instructions given at this page: https://seedsecuritylabs.org/lab_env.html

6.1.1. Download and install the virtual box first.

6.1.2. Next, download the SEED Ubuntu16.04 VM image file to a folder in your computer.

6.1.3. Unzip and copy the VM images to a folder.

6.1.4. Configure the virtual box and create a new virtual machine with the same name as your full name (e.g., JohnDoe as the name of the VM).

6.2. To hand in:

6.2.1. (10 pts) Print a screenshot of your VM created above (in 6.1.4). Note: Name the VM using your full name. Figure 2-1 shows a sample screenshot.

Figure 2-1: Sample screenshot of a VM

Note: As shown in Figure 2-2, in order to enable shared clipboard between the VM and your computer’s OS, be sure to configure, in Settings/General/Advanced, both ‘Shared Clipboard’ and ‘Drag’n’Drop’ to bidirectional.

Figure 2-2: VM settings to enable shared clipboard

6.2.2. Answer the following questions:

6.2.2.1. (10 pts) What is a virtual box? Hint: Explain its relationship to the operating system. What is the role played by the virtual box?

6.2.2.2. (10 pts) What is the role played by the SEED Ubuntu16.04 VM image?

6.2.2.3. (10 pts) How many VMs can you run simultaneously within a virtual box?

6.2.2.4. (10 pts) Start the VM created above in 6.1. Click the Terminator icon to activate a terminal window within the VM. Enter the following three commands into the terminal window: whoami, date, ls. Take a screenshot of the terminal window. See Figure 2-3 for an example screenshot.

Figure 2-3: Sample screenshot of a terminal window in the virtual box

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Lab 3

Total: 100 points

1. Review how the Euclid Algorithm works by entering 100 and 77 as the two input numbers using the online gcd calculator at https://www.calculatorsoup.com/calculators/math/gcf-euclids-algorithm.php.

2. (10 pts) Use the Extended Euclidian Algorithm (EEA) to find the values of x and y for the equation 100x + 77y = 1. Show the intermediate steps. NOTE: Always verify the derived values to ensure that they’d satisfy the given equation. When necessary, switch the values of x and y.

3. RSA key-pair generator

3.1. (5 pts) Given two prime numbers, p = 11 and q = 23. The first step of generating an RSA key-pair is to calculate the values of n and totient(n). Show how the two values are calculated.

3.2. (5 pts) Given n and totient(n), the public key (e) is selected, by making sure e < n and gcd(e, totient(n)) = 1. Can the number 21 be selected as the public key of this key pair? Justify your answer.

3.3. (10 pts) Show the first 30 numbers in the set of potential public keys.

3.4. (10 pts) Let the public key e be 51. Solve ed mod totient(n) = 1 to determine the private key d. Show the detailed steps. Hint: Use EEA. NOTE: Always verify the derived private key by checking whether it’d satisfy the original equation.

4. Hands-on lab

NOTE: Configure and run your hands-on labs in the virtual box that you set up earlier in Lab 2.

4.1. Study the Description of the “Crypto Lab -- Secret-Key Encryption” (https://seedsecuritylabs.org/Labs_16.04/PDF/Crypto_Encryption.pdf), in particular Task 2: Encryption using Different Ciphers and Modes.

4.2. Use the first question of this lab as the content of the initial plain.txt file.

4.3. Encrypt the plain.txt file into cipher.bin file using the AES-128-CBC cipher. Save the content of the ciphertext. (Case #1 in Table 4.1)

4.4. Modify the plain.txt file by adding a sentence like ‘My name is …’ at the beginning of the file. NOTE: Use your own full name. Encrypt the modified file to produce a new cipher file. Save the content of the ciphertext. (Case #2 in Table 4.1)

4.5. Modify the plain.txt file by making the first sentence as a standalone line by itself. Encrypt the modified file to produce a new cipher file. Save the content of the ciphertext. (Case #3 in Table 4.1)

4.6. (45 pts) Table 4.1 shows the three cases described above and the respective plaintext and ciphertext. Generate a table like this from your own files.

Table 4.1: Three cases of comparison between the plaintext and the ciphertext using AES-128-CBC encryption

Cases	Content of plaintext files	Content of the ciphertext files (in hex)
#1	Review how the Euclid Algorithm works by entering 100 and 77 as the two input numbers using the online gcd calculator at https://www.calculatorsoup.com/calculators/math/gcf-euclids-algorithm.php.	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
#2	My name is John Doe. Review how the Euclid Algorithm works by entering 100 and 77 as the two input numbers using the online gcd calculator at https://www.calculatorsoup.com/calculators/math/gcf-euclids-algorithm.php.	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
#3	My name is John Doe. Review how the Euclid Algorithm works by entering 100 and 77 as the two input numbers using the online gcd calculator at https://www.calculatorsoup.com/calculators/math/gcf-euclids-algorithm.php.	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

4.7. (15 pts) As shown in Table 4.1, the first several bytes of the ciphertext in case 2 and 3 are identical (as highlighted), but the rest of the ciphertext in those two cases were different. Explain the reason of this phenomenon. Hint: AES is a block cipher.

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Lab 4:

Total: 100 points

1. (10 pts) There exist dependency relationships between security mechanisms. Those relationships are part of the prerequisites of deploying a given technology. For example, the digital certificates mechanism (e.g., X.509) depends on the Digital Signatures mechanism. Explain why digital certificates depend on digital signatures, and what are implied by such a dependency (with respect to deploying digital certificates in a computer system).

2. Suppose a protocol is designed to enable secure transmission of a session key from a user to another user (in order to establish a secure session between the two). When Alice wants to send a session key to Bob, the key is to be encrypted with Bob’s public key, and the encrypted key will then be decrypted by Bob using his private key.

2.1. (10 pts) What security service(s) would be provided by this protocol. Justify your answer.

2.2. (10 pts) Revise the given protocol in order to provide confidentiality, data integrity, and origin integrity. Show the detailed steps of your revised protocol. Note: Clearly show which entity performs which operation in the protocol. You may draw a diagram to illustrate the protocol.

3. (Continued from 2 above, Protection of a session key using the recipient’s public key)

3.1. (10 pts) For this protocol to work, the prerequisite is that Alice must have Bob’s correct public key. In order to have Bob’s public key, Alice may request Bob to send his public key over. If the hacker Eve can successfully steal Bob’s public key when it is on its way to Alice, and then replace that public key with her own public key, she can succeed in deceiving Alice to trust that what she has received is Bob’s public key, creating an erroneous binding between the owner (in this case Bob) and that owner’s public key (in this case Eve’s public key). Such an attack is called man-in-the-middle attack against the public key cryptography. Explain how this attack may be mitigated? Justify your answer. Hint: Read Chapter 24 of Du’s book.

4. SSL/TLS Certificates: Suppose there exists an online company (C), and a customer (A) has visited C’s online shopping site. To earn the customers’ trust, C has a TLS certificate installed on its webserver. Note: Read Chapter 25 of Du’s book for more information about TLS Certificates.

1.1. (10 pts) Explain how C’s certificate would be created. By whom? Draw diagrams if necessary to enhance your explanation.

1.2. (10 pts) Explain how C’s certificate would be verified by A’s browser.

1.3. (10 pts) What are accomplished by the handshake process between A’s web browser and C’s web server?

1.4. (10 pts) A successful handshake between the browser and the server is followed by a secure session. Explain which of the security services (confidentiality, data integrity, origin integrity, availability, and non-repudiability) are provided in a secure SSL session. Justify your answer by explaining how each of the applicable security services is enabled.

1.5. (10 pts) Suppose H has taken C’s certificate and manually changed the subject information in C’s certificate from C to H. Would this modification be detected by A during the certificate verification process? Justify your answer.

1.6. (10 pts) Suppose a hacker has set up a rogue web server, H, and uses C’s certificate as its own certificate, and suppose A has visited H to do some online shopping. Explain how A would detect that the digital certificate presented by H is not valid.

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