Assignment 2 Comments
Good job on the homework, everyone... I've gotten everyone's key, and I have signed it for you.
As far as individual grading, the group score was given assuming that the individual parts were completed successfully... a few people sent encrypted email that I could not decrypt, so I deducted extra marks from the score listed. The grades on Web CT should reflect this.
10.10.6 - Many people got this question incorrect, and thought that a man in the middle attack would be effective... I do not think this is the case, so I deducted marks.
10.10.7 - Almost everyone got this correct, the method is effective as stated.
11.8.3 - I allowed a varity of answers for this question, as long the answers were supported well... the basic answer for part a was O(2^n), part b was not phrased well, so I gave a lot of leeway.
11.8.4 - There needs to be a pair of keys for each possible pair of hosts, solution was ~ n(n - 1) / 2
11.8.6 - Lot's of possible solutions here, I believe everyone gave an acceptable answer.
11.8.7 - PEM is designed purely for text messages, PGP can do both binary or text, hence the need for a flag.
11.8.10 - (a) Application, (b) Transport, (c) Transport, (d) Network. If there was good justification for other answers on (c) or (d), I did not take off marks.
Question 3 - These group questions were designed to make you think. Everyone created a public key, which I have signed... a few people sent email that was not encrypted using one of my keys, or was somehow corrupted.
Question 4 - Lots of good and interesting answers.
Student ID:
42349001
79956017 - Couldn't decrypt email
35595024
78058997
Score: 50/50
Questions:
(3/3) 10.10.6 -
(4/4) 10.10.7 -
(3/3) 11.8.3 -
(6/6) 11.8.4 -
(5/5) 11.8.6 -
(3/3) 11.8.7 -
(6/6) 11.8.10 -
(2/2) Question 3 (a)
(3/3) Question 3 (b)
(3/3) Question 3 (c)
(2/2) Question 3 (d)
(10/10) Question 4
Student ID:
78321015 - Couldn't decrypt email.
76873017 - Couldn't decrypt email.
Score: 42/50
Questions:
(1/3) 10.10.6 - Since the message is supposed to be random, it is unlikely the same random message would be sent, and the replay could be detected. Also, this is used to authenticate Bob to Alice, not Alice to Bob.
(4/4) 10.10.7 -
(2/3) 11.8.3 - (part d) is not correct.
(3/6) 11.8.4 - Pairs between each host... n!
(5/5) 11.8.6 -
(3/3) 11.8.7 -
(6/6) 11.8.10 -
(2/2) Question 3 (a)
(3/3) Question 3 (b)
(3/3) Question 3 (c)
(2/2) Question 3 (d)
(6/10) Question 4
More analysis was needed for this question, and there was no clear answer.
Student ID:
85051019
38080008
37250008 - Couldn't decrypt email.
Score: 48/50
Questions:
(1/3) 10.10.6 - I believe your analysis is incorrect, Alice is attempting to verify the identity of Bob, the man in the middle attack will not be effective. I think it is assumed that Alice is providing a challenge to Bob.
(4/4) 10.10.7 -
(3/3) 11.8.3 -
(6/6) 11.8.4 -
(5/5) 11.8.6 -
(3/3) 11.8.7 -
(6/6) 11.8.10 -
(2/2) Question 3 (a)
(3/3) Question 3 (b)
(3/3) Question 3 (c)
(2/2) Question 3 (d)
(10/10) Question 4
Student ID:
83556019
83313015
50891985
Score: 47/50
Questions:
(3/3) 10.10.6 -
(4/4) 10.10.7 -
(3/3) 11.8.3 -
(6/6) 11.8.4 -
(5/5) 11.8.6 -
(3/3) 11.8.7 -
(3/6) 11.8.10 -
(2/2) Question 3 (a)
(3/3) Question 3 (b)
(3/3) Question 3 (c)
(2/2) Question 3 (d)
(10/10) Question 4
Well done analysis.
Student ID:
45077005
82214016
92294016 - Couldn't decrypt email.
81220014
Score: 49/50
Questions:
(2/3) 10.10.6 - If the key is compromised, most authentications will fail.
(4/4) 10.10.7 -
(3/3) 11.8.3 -
(6/6) 11.8.4 -
(5/5) 11.8.6 -
(3/3) 11.8.7 -
(6/6) 11.8.10 -
(2/2) Question 3 (a)
(3/3) Question 3 (b)
(3/3) Question 3 (c)
(2/2) Question 3 (d)
(10/10) Question 4
Student ID:
84688019
36271005
43453000
79691010 - Couldn't decrypt email.
Score: 49/50
Questions:
(3/3) 10.10.6 -
(4/4) 10.10.7 -
(3/3) 11.8.3 -
(5/6) 11.8.4 - Since keys are distributed on a per host pair basis, it's implied there is a key for every pair of hosts... n!
(5/5) 11.8.6 - Good
(3/3) 11.8.7 -
(6/6) 11.8.10 -
(2/2) Question 3 (a)
(3/3) Question 3 (b)
(3/3) Question 3 (c)
(2/2) Question 3 (d)
(10/10) Question 4
Student ID:
74080995
79179990 - Couldn't decrypt email.
76409994
Score: 48/50
Questions:
(1/3) 10.10.6 - I don't think a man in the middle attack will work, you need more details to support your claim.
(4/4) 10.10.7 -
(3/3) 11.8.3 -
(6/6) 11.8.4 -
(5/5) 11.8.6 -
(3/3) 11.8.7 -
(6/6) 11.8.10 -
(2/2) Question 3 (a)
(3/3) Question 3 (b)
(3/3) Question 3 (c)
(2/2) Question 3 (d)
(10/10) Question 4
Student ID:
81307993
45970985
81278996
Score: 49/50
Questions:
(2/3) 10.10.6 - If they key is compromised, any crypto system will fail.
(4/4) 10.10.7 -
(3/3) 11.8.3 -
(6/6) 11.8.4 -
(5/5) 11.8.6 -
(3/3) 11.8.7 -
(6/6) 11.8.10 -
(2/2) Question 3 (a)
(3/3) Question 3 (b)
(3/3) Question 3 (c)
(2/2) Question 3 (d)
(10/10) Question 4
Student ID:
80532039
11721040
88641030
Score: 50/50
Questions:
(2/3) 10.10.6 -
(4/4) 10.10.7 -
(3/3) 11.8.3 -
(6/6) 11.8.4 -
(5/5) 11.8.6 -
(3/3) 11.8.7 -
(6/6) 11.8.10 -
(2/2) Question 3 (a)
(3/3) Question 3 (b)
(3/3) Question 3 (c)
(2/2) Question 3 (d)
(10/10) Question 4
Student ID:
41192022 - Couldn't decrypt email.
39129002
37861002
40790024
Score: 50/50
Questions:
(2/3) 10.10.6 -
(4/4) 10.10.7 -
(3/3) 11.8.3 -
(6/6) 11.8.4 -
(5/5) 11.8.6 -
(3/3) 11.8.7 -
(6/6) 11.8.10 -
(2/2) Question 3 (a)
(3/3) Question 3 (b)
(3/3) Question 3 (c)
(2/2) Question 3 (d)
(10/10) Question 4
Student ID:
41169020 - Couldn't decrypt email.
45576022 - Couldn't decrypt email.
Score: 50/50
Questions:
(2/3) 10.10.6 -
(4/4) 10.10.7 -
(3/3) 11.8.3 -
(6/6) 11.8.4 -
(5/5) 11.8.6 -
(3/3) 11.8.7 -
(6/6) 11.8.10 -
(2/2) Question 3 (a)
(3/3) Question 3 (b)
(3/3) Question 3 (c)
(2/2) Question 3 (d)
(10/10) Question 4
Student ID:
47414982
27017953
15051956
Score: 50/50
Questions:
(2/3) 10.10.6 -
(4/4) 10.10.7 -
(3/3) 11.8.3 -
(6/6) 11.8.4 -
(5/5) 11.8.6 -
(3/3) 11.8.7 -
(6/6) 11.8.10 -
(2/2) Question 3 (a)
(3/3) Question 3 (b)
(3/3) Question 3 (c)
(2/2) Question 3 (d)
(10/10) Question 4