5.1-5.4 due October 2

1. Well first off, this whole section was confusing from the beginning to the end. The algorithm in 5.1 made sense for the most part, but the in depth part in 5.2 was pretty cryptic to me(haha). I think it would be amazing if we went over the different layers in depth(with examples!) to show how they actually work!
2. I noticed in 5.1  that the first transformation - ByteSub - that it is a non-linear layer that is used for resistance to differential and linear cryptanalysis attacks. It kind of caught my eye, we haven't really used any sort of differential attacks(to my knowledge at least). I'm sure I'll regret saying it later, but it sounds interesting and like a good challenge to try.

Feedback due September 30

• How long have you spent on the homework assignments? Did lecture and the reading prepare you for them?
• I spend about 1 to 2 hours on the homework, depending on how difficult it is. I feel that the reading prepares me the most for them, but that if there is a hard concept that learning about it more in depth in class helps me out more then the reading.
• What has contributed most to your learning in this class thus far?
• Honestly, I think that Google has helped me the most in learning in the class. If there's something I can't understand very well, I usually go to Google because I usually don't have time during office hours to talk to the professor. I'm a pretty visual learner, and there will usually be at least one website that helps me to understand in the most effective way.
• What do you think would help you learn more effectively or make the class better for you? (This can be feedback for me, or goals for yourself.)
• I think that what would and already helps me the most in the class is examples. The more, the better. If I can follow along to an example, it helps me to understand the homework so much more, especially if I get stuck on something I maybe don't understand very well. I think classtime is used the most effectively when we go over the material to help clarify for the first half, then spend the second half going over examples to help understand even better.

3.11 - 3.11.2

1. I was pretty confused with the first section of this chapter. They give us an example with four elements, GF(4) = {0,1,w,w^2} and the laws
1. 0 + x = x
2. x + x = 0
3. 1 * x = x
4. w+1 = w^2
I guess I'm just a little confused. Is this in a mod2? mod4? Or is it its own mod? Also what is the notation GF(4)? Maybe it was said in a different chapter, but I don't remember reading about it. They use the same notation later in 3.11 as well, but I don't understand what it's supposed to mean.
2. I am using division with functions right now in my number theory class, as well as teaching it to my students for math 110. It's kind of funny how I'm doing it in three different places! It makes it a little easier to understand after doing it three times in one day. Hopefully this section won't be too hard.

4.5-4.8 due September 25

1. I had a hard time understanding DES in class last time, and reading about it again confused me still. I was the most confused with the Output Feedback, just reading it and looking at the diagram made me super confused. We should definitely go over it in class. We could go over the Counter and Cipher Feedback as well, but those two weren't quite as hard to understand.
2. I liked reading about how the RSA held a couple contests to break a DES cipher. I actually was really surprised that the first time it only took 5 months! I was honestly expecting at least a year. But it was even more surprising to see that the second contest a year later only took about 40 days! That's such a big difference in so little time. It really does show that the DES cipher is pretty dated with new technology coming out. I'm excited to see if there is anything even more hard(and confusing) to crack.

4.1, 4.2, 4.3 due September 23

1. This section was a handful! I was having quite the time trying to understand what was being talked about. This will be weird, but the hardest part for me to understand were actually the diagrams. I would think I had something figured out, then looking at the diagram, like Figure 4.1 on page 115, the Feistel System, I would be lost again. I don't think it was very explanatory, or at least comprehendible. I would like examples in class of basically everything, but mostly what was talked about in section 4.2.
2. First off, in the introduction, I thought it was pretty funny that the IBM algorithm was called LUCIFER. I think it would be pretty great to know if it actually just happened that way, or if the people who made the algorithm chose to call it that because it's a beast or something. I thought that it was pretty cool that it was so recent though, in 1974, because its a lot more relevant to what we have learned recently.

2.9-2.11 Due September 20

1. I was having a hard time understanding Linear Feedback Shift Register Sequences. It looks like it might just be a simple formula, but I guess whats confusing me is how you can get a lot of different keys from that. I feel that a lot of keys will be similar and there won't be as much variety. But I also think I might be misunderstanding what the method is all about. If there's anything I want an example of in class, it would be this.
2. I was pretty intrigued that one-time pads are basically unbreakable. I think with the modern age of computers, that this wasn't possible, but after reading I understood that it could be possible. I still think that it might be at least plausible if you had the worlds fastest computer to try to decrypt it, but even then, it is so simple, yet so hard to break. I liked the example that FIOWPSLQNTISJQL could be either wewillwinthewar or theduckwantsout in plaintext. It shows that there are so many ways the code could be decrypted and make sense, but still not be right.

3.8 and 2.5-2.8 due September 18

1. One thing that confused me were the ADFGX ciphers, as well as the block ciphers. It was a lot of work, and made it a little hard to understand.  I guess it was the fact that not only we have a keyword, but we're only putting part of the message into a matrix, then crypting the message seprately. At least that's what I think it meant. As with everything in this book, an example would be nice in class, probably for the Playfair, ADFGX, and Block ciphers.
2. I always say that I like the history of cryptography, and this section was just as good. I think my favorite part was learning about the ADFGX cipher, and how it was used by the British forces. The fact that it was deciphered by French cryptanalyst Georges Painvin was pretty great, and how they were able to decrypt a lot of messages. I wonder how long it took the British to realize they'd been compromised!

2.3 Due September 16

1. Well, this whole section was pretty confusing. I think it was just a hard to understand the shifting then using the matrix with probabilities. I'm able to understand it more in class when it's done visually on the whiteboard step by step, so hopefully that will help!
2. For the project 4 we were supposed to do, I was originally thinking about using matrixes to code and decode a message. This process seems like it could have been used to crack my code, and I hadn't even thought of it that way before! I think the process isn't quite as complex as it seems right now, but I think that once I understand it I will probably like this specific process.

2.1-2.2 and 2.4 due September 13

1. The one thing I was having a hard time with was section 2.2. I understand how to use modules, but how they were using that to encrypt a function wasn't making sense much. I was also confused at the four 'sections' of "ciphertext only, known plaintext, chosen plaintext, and chosen ciphertext" and what they meant. In the last two it would say something small like choose the letter a as the plaintext, and how it gives the key. I guess it's probably simple, but it wasn't really making sense at how having one letter gives away the key.
2. The thing I liked about these sections were how they talked again about historical times encrypting messages was used. I thought the example of Julius Caesar was really cool because of how simple his ciphertext was, but it probably was something relatively unknown to most people so it made it advanced for their day. I also liked the example of Thomas Jefferson and Benjamin Franklin. It was basically the same concept, yet so many years apart. We're definitely part of a great generation, where we can use computers to make such advances in cryptography.

Guest Lecture, due September 13

1. During this lecture, the only thing that was hard for me to comprehend was the Deseret Alphabet. I guess every sound had one symbol only, and this to me just didn't seem like it would be possible to turn into an alphabet. There are just so many different sounds you can make phonetically, it seems like you couldn't manage to make a symbol for each sound. But I am a little biased I'm sure, since I only know English and it's alphabet.
2. One thing that I thought was really interesting was the crypted names in the Doctrine and Covenants. It was super cool that they substituted names with such unusual ones, but funny that they didn't keep their own key so there were some names that no one remembered. They had to piece things together years after to remember the names.

3.2 and 3.3 due on September 9

1. I think the difficult part of the text today was basically all of 3.2. We are trying to solve ax + by = d, which I understand, but this part of the text was really hard to follow, and the explanation left me more confused then before. It would be nice in class to get a better explanation with an example.
2. 3.3 reminded me of my proofs class I took 3 years ago. We kind of glossed over mods, but that class is the only other place I remember even learning about it. I just remember my professor telling us that it is very useful in cryptography, so I am excited to see the connections and how useful it really will be!

1.1-1.2 and 3.1, due on September 6

1.  I am learning the same thing about gcd's and Eucilds algorithm, so none of this is especially new. I think the only thing that looks little difficult is the Prime Number Theorem. I am just a little confused at how it works. It would be nice to have an example in class and seeing how it is important.
2.  So far, what I think is interesting is all the examples of cryptography from WWI and WWII. It's cool to see how compared to then, how complex it is to send a secret message. I especially liked the example of the Germans sending a message saying everything is normal, when it was actually encrypted with a new key each day.

Introduction Due on September 6

• What is your year in school and major?
• I am a senior graduating this semester in Mathematics
• Which post-calculus math courses have you taken?  (Use names or BYU course numbers.)
• 290, 300, 313, 314, 334, 341, 342, 352, 360, and 371
• Why are you taking this class?  (Be specific.)
• I am planning on applying to the NSA after I graduate, and I feel like this class will be really helpful in gaining experience.
• Do you have experience with Maple, Mathematica, SAGE, or another computer algebra system?  Programming experience?  How comfortable are you with using one of these programs to complete homework assignments?
• I have not had experience with Maple, Mathematica or SAGE. I have had programming experience in Java and R. I think I will be fine using any program given.
• Tell me about the math professor or teacher you have had who was the most and/or least effective.  What did s/he do that worked so well/poorly?
• I think teaching straight from the textbook is what makes a math professor very hard to follow. What is helpful in my experience is when a professor gives examples that are not in the book. It gives you more experience in what you're learning and something else to refer to if you are confused.
• Write something interesting or unique about yourself.
• I like to draw with chalk, I am participating in the Chalk the Block in the Riverwoods this coming week.
• If you are unable to come to my scheduled office hours, what times would work for you?
• I will be ok.