Question 17 Answer saved Marked out of 1.00 In Section 2.7, the UDPserver described needed only one socket, whereas the TCPserver needed two sockets. Why? If the TCPserver were to support simultaneous connections, each from a different client host, how many sockets would the TCPserver need? Select one: Flag question O a. N 2 b. N(N+1)/2 d. N2 e. N f. N 1 Question Not yet answered Marked out of 1.00 Mary receives from Bob, an extended message that contains the message along with a message authentication code (MAC). The message has Bob's medical preferences, A, B and C, should he have an accident and cannot communicate. Bob has an accident and is unconscious. Would Mary's claim that Bob's medical preferences are A, B and C, based on the message from Bob that has the MAC, hold up in court of law ? (note -this is not a legal question, so don't look Google if MAC is acceptable in court - it is a hypothetical situation for a technical question on understanding MAC) Flag question Select one: a. Yes - the digital signature included in the MAC is proof of a b. No - the MAC is insufficient to prove authentication c. No - the MAC would be sufficient to prove authentication and for integrity of the message but insufficient evidence for proof that the document could not forged d. Yes - the MAC proves the message is from Bob, that Bob's preferences in his message have not been changed and that his preferences were not forged. integrity and non-repudiation Question 19 Not yet answered ntegrity and non-repudiation? Marked out of 1.00 Are digital signatures using a public-key encrypted message and one from a public key encrypted message hash equivalent in terms of proving a Select one: Flag question a. No - they are not equivalent, RSA is expensive, encrypting an entire message takes more time so non-repudiation cannot be proved b. Yes - they are equivalent in terms of proving the security objectives of authentication, integrity and non-repudiation. c. Yes- they are not only equivalent in proving the security objectives of authentication, integrity and non-repudiation, they are also the same in terms of processing cost. d. No - they are equivalent in terms of processing and compute cost but they are not equivalent in terms of non-repudiation, digital signatures can prove non- forgery but not non-repudiation Question 20 Not yet answered Marked out of 1.00 Alice has 3 good friends who live in various parts of the country from her. She wants to send electronic messages to her friends. She can use a MAC to send along with her messages to her friends. She also can use public key encryption - she has a public key and private key pair which she has not registered in a CA, though, because she is not a business and because of the cost. Her friends want to be sure of the integrity of the message. In this context, which scheme is more suitable - Alice using her private key to sign her messages or for her to use MAC? Flag question Select one: a. MAC is better because key distribution is not a big problem with just 3 friends. Without Alice's public key pair being registered, Trudy could masquerade as Alice with a woman in the middle attack. b. For a MAC-based scheme, Alice would have to establish a shared key with each potential recipient. With digital signatures, she uses the same digital signature for each recipient; the digital signature is created by signing the hash of the message with her private key. Digital signatures are clearly a better choice here. c. The MAC is better because it is less compute intensive and sending her friends her private key is easy to do. d. Using a public key cryptography scheme is superior - it provides authentication, integrity and most important -non-repudiation so Alice could never claim she never sent the message. You cannot prove non-repudiation with MAC so it would be better for Alice to use her private key to sign her messages