Hw #3 - Network Security

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University of North Georgia, Dahlonega *

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3510

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Computer Science

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Dec 6, 2023

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docx

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3

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CSCI 4650 Network Security Homework #3 Please refer to the syllabus for expectations of homework professionalism and appearance. Your homework is expected to be an individual effort. It is also expected to be neat and clearly organized. The University provides access to many software applications. Use them. Hand written papers and poorly drawn diagrams are not acceptable. You must submit the softcopy (either Word of PDF) of your homework by the specified due date and time. You can find the link for your softcopy submission in D2L This homework is due: April 4, 2023, 11:59 PM Total points: 3 1. [1 pt] Consider a one-way authentication technique based on asymmetric encryption: A. A → B: IDA B → A: R1 A → B: E(PRa, R1) B. A → B: IDA B → A: E(PUa, R2) A → B: R2 IDA = A’s ID R1 and R2 = a random number PRa = A’s private key PUa = A’s public key
Explain each protocol (A and B) and what type of attack each protocol is susceptible to. A : Authenticating A to B R1 serves as a random number and only A is able to encrypt R1 so that it can be decrypted with A’s public key. A type of attack would be if someone(C) can use this mechanism to get A to sign a message then C will present this signature to D along with the message claiming that it was sent by A. This becomes a problem if A uses its public/private key for both signatures etc. B: Authenticating A to B only A can decrypt the second message to recover R. A type of attack could be if someone(C) can use this mechanism to get A to decrypt the message for example sent that message as R2 meaning that it has eavesdropped from the network originally sent to A 2. [1 pt] In Kerberos, A) when Bob receives a ticket from Alice, how does he know it is genuine? B) when Bob receives a ticket from Alice, how Does he know it came from Alice? Anwser: AS verifies user’s access right in the database, and creates ticket- granting ticket and session key. Results are encrypted using key derived from user’s password Then the workstation prompts the user for password to decrypt the incoming message then sends the ticket and authenticator that contains the user's name , network address, and time to TGS. TGS decrypts ticket and authenticator and verifies request and then creates ticket for requested application server. 3. [1 pt] Consider the following protocol: A → KDC: IDA || IDB || N1 KDC → A: E(Ka, [KS || IDB || N1 || E(Kb, [KS || IDA])] A → B: E(Kb, [KS || IDA])
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