Exam 1, due on October 1

• Which topics and ideas do you think are the most important out of those we have studied?
• All of chapter 3
• DES
• AES
• What kinds of questions do you expect to see on the exam
• Decipher using any of the methods learned
• Use of the mathematical tools learned 
• Questions about attacking systems 

• What do you need to work on understanding better before the exam?
• Methods of Attack
• Modes of Operation
• DES

5.1-5.4, due on September 29

1. It was a little bit hard to remember which step was which as I was reading along. I'd have to keep looking back a page or two to remind myself what BS, SR, MC and ARK meant. Also, in section 5.4, it's hard for me to see why the design used escapes the attacks mentioned.

2. It is interesting how fast diffusion occurs in Rijndael; that in two rounds, all 128 output bits depend on all 128 input bits. Another thing I like about this system is the simplicity of the s boxes. These s boxes seem more practical than those in DES.

Questions, due September 27

1. I have probably spent an average of 3 hours on each assignment. I feel that they were very fair and kind of fun. The lectures and reading did prepare me for them.

2. The assignments and lecture have contributed most to my learning. The book is okay in general, but sometimes I feel completely lost while reading it. When I go to class the next day I understand most of the material without much of a problem.

3. I feel like I need to spend more time and concentration on the readings. If I really plugged through it and tried harder to understand what is going on, I think I'd learn better.

3.11, due on September 24

1. I don't really understand the concept of generating polynomials. There wasn't really a definition in the text unless I missed it. Also, I had a hard time making the connection between these polynomial fields with LFSR sequences. I understand when it talks about GF(2^m) as a vector space over Z_2, but as soon as it introduces the matrix M_x I get lost.

2. My favorite part of this class so far is the math. Like I've said in the past, I'm a math major and I don't know any computer science, so it's refreshing to read a chapter that's written in my language. It is interesting how much F[x] has in common with the integers. I have never thought about the polynomials in that way.

4.5-4.8, due on September 22

1. I thought this entire reading assignment was difficult. I don't know a think about computer science and I feel like this text makes the assumption that the reader is familiar with cs. Also, I wasn't able to follow the way most concepts were explained. Hopefully things will make more sense in class.

2. I suppose it is interesting that methods were developed which can attack DES so quickly. I haven't the faintest idea what those methods are or how they work, but it seems incredible that such an intricate and complex system.

4.1-4.2, 4.4, due on September 20

1. The last part of section 4.4 was hard for me to follow. It may be because I haven't completed a course in Abstract Algebra and am therefore unfamiliar with group theory. Besides that, the trickiest part of this reading assignment was keeping track of all of the steps involved in DES. There are several parameters to keep track of within each step of the algorithm.

2. I loved reading about DES! I imagine that the guys who came up with it had a great time inventing it. It is so complex and intricate that I can't imagine how it can ever be broken. But I guess computers these days are a bit smarter than me. My favorite part was that if I went slowly enough, I was able to follow every step of the algorithm. I feel confident that if given enough time (days), I could successfully encrypt a short message using DES.

2.9-2.11, due on September 15

1. I really struggled with this reading assignment. I don't know a thing about computer science or programming so a lot of the terms and language that the book used went way over my head. I especially didn't understand most of section 2.11. Specifically, the proof at the end of 2.11 was really hard for me to understand.

2. It is really interesting to me that so much information can be communicated using just the numbers 0 and 1. Intuitively it doesn't make sense. I also liked how using certain random bit generators are able to reduce the number of bits needed to create much bigger keys.

2.5-2.8, 3.8, due on September 15

1. Basically this whole reading assignment was difficult for me. I didn't really have a hard time understanding how to encrypt or decrypt any of the ciphers, but I struggled understanding why the attack methods would work. This was especially true for the Playfair and ADFGX Ciphers.

2. I really love linear algebra. It has been my favorite subject since I've been studying math. So it is exciting to see it used in Cryptography. Not only is it used, but it seems to be really valuable.

2.3, due on September 13

1. I struggled a little bit with the part where the book explains why the method they showed for finding the key length works. It kind of makes sense to me, but if I were asked to explain it to another person, I'm not sure how well I'd be able to do it.

2. I loved learning the ciphertext only attack of this method. As I read the first couple pages explaining the method, I couldn't think of any way to possibly break the code. After reading the whole chapter, however, it was amazing to see how simple it is to break. Even though I'm still not totally clear on how it works, it's really cool to see probabilities working to the cryptanalyst's advantage.

2.1-2.2 and 2.4, due September 10

1. I had a hard time understanding the chosen plaintext and chosen ciphertext methods of attack for the affine cipher. The rest of 2.2 was pretty understandable, but I didn't quite understand the methods of attack, especially under the chosen plaintext when it says "The first character of the ciphertext will be alpha*0+beta=beta..." Maybe I just need to try to better understand the general ideas of chosen plaintext and chosen ciphertext.

2. My favorite part of the reading was in section 2.4 when it decrypts the declaration of independence. It was really cool to see letter frequency and pair frequency actually used to decipher such a seemingly difficult ciphertext. I'm going to use the letter frequencies given in the book to my advantage in hangman.

Guest Speaker, due on September 10

1. I struggled with the concept of the Deseret Alphabet. If it was something the Saints deemed important enough to develop, why is it not used anymore? It seems to me that it would still be valuable for children to learn in addition to the English Alphabet.

2. The whole presentation really held my attention. Cryptography isn't something I'd readily connect with church history. The speaker really opened my eyes to the importance of ciphers in the history and development in our Church. My favorite cipher discussed was the pig pen cipher, mostly because it looked almost like some middle eastern language, but is actually constructed very simply.

3.2-3.3, Due on September 3

1. I haven't completed abstract algebra, and therefore haven't worked with modular arithmetic very much. The most difficult part of this reading was shifting my way of thinking from real number arithmetic to modular arithmetic.

2. The most interesting part of the reading for me was at the end of 3.3 when it talks about fractions and dividing. The whole idea of multiplicative inverses is brand new to me and I find it pretty cool.