18.1 and 18.2 due November 26

1. I was a little confused about Error Correcting Codes. About to the Notation on page 401 it starts talking about code lengths and codewords... what is the difference? I think I am confused too on what distance is too. Equivalence was also throwing me off a bit too. How are they equivalent when we Permute the symbols? It's all really new and I have to remember sets and stuff again..
2. It's interesting how cryptography and coding theory differ. One is sending messages over nonsecure channels, and one is sending messages over noisy channels. I wonder if there are times when both are used at the same time? I could see someone failing to send a clear message with the examples we learned about with one time pads, where the random integers were made from computers or other random-ish things. In circumstances like that though, it seems like a ciphertext would be even easier to break since you might need to send the key more then once, but could also have potential to be harder to break! I wonder which it really is.

2.12 due November 25

1. I got a little lost during the explanations of solving the keys to find the rotation used for that day. They talk about using the first and the fourth letters since they would be the same plaintext, but I wasn't sure if it was for just one key at a time, or for all the different keys we were given at once. Then they talk about how the permutation A sends k to d and D sends x to v. Where are they getting those from? Then it feels like out of nowhere they know what x is! So confusing..
2. I've always mentioned in my posts that I love history. This was no exception. What a cool concept the Enigma was! It seemed like a really creative and "out-there" type idea, I was surprised that the British were able to crack the codes and keep them secret for 30 years. It was really lucky for them, it seems like something like that where it was essentially one of the first electronic computers would be a lot harder to crack, but somehow they did it! Kudos to them for sure!

19.3 due November 22

1. After looking at the website and then the book, I still have a little bit of confusion. At the beginning of the chapter, they talk about how we are trying to find an a and r such that a^r = 1(mod p) but in the example, we get to the point where 11^x-y = 1 (mod p). I think that's the point we were trying to get to, but wouldn't x-y=0? Maybe I am wrong, but I didn't think that this would work.
2. I was very surprised in the example when they said that a quantum computer couldn't use 21 like we could do in the example in our book! It seems like such a small number, and it shows we still have some progress to make in this field! It makes me think about how conspiracists believe that the NSA has a super quantum computer that could do anything! That would be interesting if they did, and would actually probably help public advancements in the future!

19.1-19.2 due November 20

1. Well, this whole section was confusing. I think the worst part was all the arrows. I really didn't understand what they meant. I know that they are bases or something, but I don't know what they represent at all, which made it hard to understand the rest of the section.
2. I definitely did not think we would talk about quantum mechanics in cryptography! It looks like in the introduction that it is still a young concept, and so we don't discuss it much, but I think that it has a lot of interesting potential for the future!

Review due November 15

• Which topics and ideas do you think are the most important out of those we have studied?
• I think that RSA and discrete logarithms are the most important topics that will be on this test.
• What kinds of questions do you expect to see on the exam?
• I am expecting a continued fractions question, a discrete logarithm question, a hash function, and maybe a RSA signature question that isn't too hard.
• What do you need to work on understanding better before the exam?
• I think what I need to work on the most is discrete logarithms. It played a big role, and I wasn't the best at solving discrete logs. I think most the time I got them wrong, though I do understand the concept and how to solve it.

12.1-12.2 due November 13

1. I definitely got a little lost in the middle of 12.2. They mention for the Shamir threshold scheme splitting the keys into subsets so that a smaller amount of people can get the message. But to me, it looked like they were still using everyone to get the message. Then they put it into a matrix and take the determinant for some reason. That's about where I got lost and felt like I was just reading without even understanding what I was reading! Clarification on this would be most helpful.
2. At the very beginning of 12.2 they mention having a mechanism where two out of three keys will control a weapon. I literally thought about a spy movie before I read the line that mentioned it. They use  a similar method in the White House Down movie that just came out. To launch a missile, there were three people that needed to give their authentication, including the president. It was a nice, cheesy thriller with Channing Tatum in it. It's cool that this concept is used in cryptography.

9.1-9.4 due November 11

1. These sections were pretty straightforward, but I feel like I might not understand quite fully what is happening. They mention in the introduction of chapter 9 that we are not trying to encrypt m at all, but in 9.1, Alice's signature is m^dA. Isn't this encrypting m then? I think there is something I am not quite getting.
2.  I was very interested in the birthday attack. It seems interesting to me to try and create two separate documents, and change them just slightly to try and make it so both have the same hash, then use their signature against them. At the end, they mention to do something small, like remove a comma, or any slight alteration to foil this method. I wonder how this would actually work in some cases. But I also am intrigued by the idea, especially after our last homework where we basically made two hashes similar in this way.

8.1-8.2 due November 5

1. I am not feeling good, so I was having a hard time understanding hash functions in general, but my main question I was wondering is why when h(m1) = h(m2), m1≠m2. Is it just the way that a hash function works that there are many ways to interpret it? I don't understand if we are encrypting and decrypting a function or not in this chapter.
2. I don't have much to reflect on. I am kind of out of it - I went into anaphylactic shock today and now I'm on some meds that are making me really tired. But I was trying to look at examples online about hash functions, and I noticed that they mentioned caches as an example. I always wondered how caches work, I know they do it for websites when you google it. But I couldn't quite understand how they work. But it's still interesting to me.

7.3-7.5 due November 4

1. I was a bit confused about the instructions in 7.5. I don't see hoe bob computing tr^-a mod p will give him the message m. They give us the reason why, but it wasn't really helping me. The whole process seemed pretty confusing to me.
2. Along with the process seeming confusing, it also doesn't feel like it's very secure. All eve needs to figure out is a. The only thing preventing her is the fact thy it is hard to compute discreet logs is very hard. But I feel like it could be done on a very good computer. I personally would not use this method.