Questions, due September 27

The homework assignments have taken me a 2-3 hours to complete. The lectures and the reading have definitely been beneficial to do the homework.

I have liked how we have looked at simple examples in class, like "baby DES" as it helped to understand it larger version. I think that it is easier to learn in class because I have read beforehand.

I think that it would help if we had homework more than just once a week, so we could better understand some of the alogrithms and ciphers better.

Sections 4.5-4.8, due September 23

I think that double encryption in DES is interesting in that it does not offer double security. Instead of searching for a pair of keys, you rather search for all of the first keys and save them all to memory. Then search for the second key and see if any of them match up, which is called a meet in the middle attack.

I didn't really understand about different kinds of DES. Could you go over the five different modes in class tomorrow. I think that it was just a lot of information to digest all at once.

Sections 4.1,4.2 & 4.4m due September 21

I thought that DES was very interesting. I have never seen a cryptographic algorithm like this before and with it multiple rounds and different steps. I understand how it works, kind of, but I did not completely understand the specific details of the encryption/decryption process.

In the introduction, it said that some people were afraid that IBM or the NSA had put in a trapdoor in the algorithm. This is interesting because this is what Dan Brown's novel Digital Fortress is about. Do you know if there have been recorded instances of people or organizations getting caught with a trapdoor?

Sectiion 4.8-4.11,due September 18

I never realized how difficult it was to create a random sequence. I though a random number generator on the computer would work out just fine. I guess I was mistaken.

If there was a secure way, or less expensive way, to transmit the key one-time pads would not that be ad. For our project, we used a scripture as the key. Agreeing upon a well-known passage would be very cheap, but not very secure, though.

Sections 2.5-2.8,3.8

The cipher used in the Sherlock Holmes book was pretty much a substitution cipher, although it would be impressive that he could solve it with such a short ciphertext. I think it is interesting that we can use matrices to encrypt things as well. I didn't like the ADFGX code very much because it required a keyword and a key matrix in order to make it work.

It does seem kind of foreign doing matrix algebra and modular arithmetic at the same time. I think that it would be good to go over in class tomorrow. It is hard to keep everything straight.

Section 2.3, due September 14

I was kind of hard to understand the second method of finding the key. The first one made sense. But I didn't really get how they used the vectors of each shift to find the key.

I think that it is pretty ingenious some of the ways that cryptanalysts discover to break a code. I can see why it took them a very long time to figure out a mehod on how to find the key length and the actual key.

Sec 2.1-2,4, due September 11

Although the alphine cipher is a lot easier to break using brute force than a substitution cipher, the key used is a lot simpler. I find it interesting that a lot of times there are trade-offs between things. This time it is security vs. simplicity of the encryption key. Other times it is time vs. security.

It is kind of difficult to think about fractions like 1/9 as the inverse of 1/9 rather than the actual fractions. We didn't use fractions at all when dealing with modular arithmetic in math 371.

Wednesday, September 9

One thing that I thought was very interesting was the fact that they used simple substitution ciphers to encrypt their messages. We think of those types of ciphers as easy to solve, but that was all they needed to do to securely hide their message. The jumps in cryptology have been very larger in the last 150 years than all of the years before it.

I think that it would be pretty hard to learn the Deseret alphabet. I agree that once the letters were learned it would be easier reading. Reading a phonetic alphabet would be a lot easier than reading and pronouncing English.

3.2-3, due Friday Sept. 4

I think that it is interesting looking at nonlinear congruences. When x-squared is congruent to 1, it is basically solving for which numbers are their own inverses. The book said that for all odd primes plus or minus 1 mod p are the only solutions. I would like to know if there are similar results for x-cubed and so on.

I think that solving modular equations was the part that was most difficult in these sections. I never remember that they are a lot easier to solve once you have done the extended Euclidean Algorithm.

1.1-1.2 and 3.1, due on September 2

While most of this was review, I did learn that PKC is significantly slower than symmetric algorithms. While PKC is very hard to break, it is only used to send digital signatures or keys to the symmetric algorithm.

I think that it is kind of difficult to understand how some algorithms are slower than others without actually knowing very much about said algorithms. Of course, this will soon go away when we learn more about symmetric algorithms and PKC. I know a little about RSA, but I am excited to learn more about the other kind of PKC algorithms.