14.1 & 14.2, due on November 14

The Interesting

I have always wondered how the little card swipers keep my information secret, so this is cool. I like the idea of the tunnel/hallway with the door in the back.

The Challenging

I don't understand why knowing that r1 and r2 factors of s mod n makes it so we know that x1 is r1^2 and x2 is r2^2. This seems like it's going to be really easy once I hear you explain it, but right now it's confusing! That made it hard for me to understand the Feige-Fiat-Shamir identification scheme and the following identification scheme they explained

12.1 & 12.2, due on November 12

The Interesting

When I first glanced at these two sections, I was a little nervous seeing all of the capital pi nutation, but then the first section made it seem manageable. This entire time reading it though, I just thought to myself, what's stopping his kids from coming and just trying all of the different numbers? They could still totally hack this and it doesn't seem very secure. 

I liked that we get to use matrices, they've always been a favorite. 

The Challenging

I cannot see why the determinant of the matrix is the product of the difference of the different x values. 

If two people tried to break the example with their numbers, why do they get a quadratic polynomial and why does that mean that any secret can still occur?

I don't understand how the Shamir method makes some people more important than others. 

Test 2 Preparation, due on November 9

Which topics and ideas do you think are the most important out of those we have studied?

 I think that RSA is a huge part of this exam: using it, knowing how it works, knowing how to do it, its weaknesses and strengths, etc.

I also think that knowing the methods for factoring, determining primality, and cracking the posed discrete log problems will be important. 

What kinds of questions do you expect to see on the exam?

I expect that we will be decrypting RSA messages.
I bet we do a Chinese Remainder Theorem question. 
I think we'll test numbers to see if they are prime (and factor if they aren't).
I bet there will be a question about the birthday attack somehow, because it's fun.

What do you need to work on understanding better before the exam?

I need to memorize the rules of the Jacobi symbol manipulation. I'll need to remember how to find square roots Mod n. I need to review the ElGamal methods and how to do them, as well as the primality determination methods. I will also really need to spend some time trying to understand signing documents in RSA, because that's still pretty fuzzy for me.

8.3 & 9.5, due on November 7

The Intriguing

I feel like it's really hard to just read about SHA-1 and understand what's happening until I actually have a message and am either watching it get encrypted with the method or if I'm trying it myself. I am sure we'll try them for homework and am excited. This was a fun reading because we talked about the DSA in class today a little so it made sense. 

The Challenging

What is a "Message Digest"? The book refers to the final Xl of SHA-1 as a message digest and I'm not sure what that means. .....And then I kept reading and was even more baffled by page 225. It seems hard to understand the SHA-1, but like I said in the intriguing, I think I will understand more by trying it out. 

9.1-9.4, due on November 5

The Captivating

I think it's crazy that there's such a thing as a blind signature. I don't know that I would ever feel comfortable signing a hash without knowing what I'm signing.

The Challenging

So in the ElGamal, Eve can solve it if both Bob and Alice use the same value for k?
I think it's crazy that changing one comma or space a bunch of times can result in finding a message with the same hash. Cool! I don't really know if I believe that this is possible, but it's still cool. To be honest, I don't really understand why the ElGamal system works with the multiple exponents.

8.4-8.5 & 8.7, due on November 2

The Interesting

I really liked learning about the Birthday Paradox. The entire time I was reading it I felt interested, I would have a question, and then the book would immediately after answer that question I had. I think I want to play the licence plate game in the car and test it out.

It was fun reading 8.7 because we talked about it in class today so it made sense. Hooray! 

The Challenging

To be honest, I understood the Birthday attack when they were using specific examples but it started getting fuzzy when they were generalizing the idea. I don't think I understand it as well as I could. However, I definitely understood them much more than I understood the section on multiple collisions. I read it three times and still didn't understand what was going on. 

8.1-8.2, due on October 31

The Thrilling

I was excited to see that this chapter heading was "Hash Functions" because the first thing my husband said when I told him I was enrolled in this cryptography class was something about hash functions. I had no idea what he was talking about, but now, I'm semi-knowledgeable! Plus, it's cool that they're used for digital signatures so all of my signatures on checks that get scanned are securely documented, but safe from being hacked into.

The Haunting (October 31... get it?)

I'm assuming that "array" means matrix...
So we learned how to get our Hash Function by XORing the different columns of the matrix (sometimes after rotations) but how do we use it? Is it supposed to be the one-way function we'd use in another system?