Cryptography

The History and Mathematics of Codes and Code Breaking

Month: September 2014 (Page 1 of 6)

Problem Set #4

Here's your fourth problem set, available in both Word and PDF formats: Problem Set 4 (Word), Problem Set 4 (PDF). And here the two Excel files you'll need to tackle the ciphertext this week: Vigenere Cryptanalysis (4 Letter) and Vigenere Cryptanalysis (5 Letter). If you need a version of these files for a different keyword length, you'll need to create it yourself using these as a model. And if you need help doing that, just let me know.

Problem Set #4 is due at the beginning of class on Friday, October 3rd.

Coffee shop owner attempts to protect customers' privacies

One passage that stood out to me while reading Little Brother was on pages 90 and 91. Here, Marcus speaks with the owner of a Turkish coffee shop. As Marcus tries to pay for his coffee with a debt card, the owner explains to him that he no longer takes debt cards. He explains that this is now just another way for the government to keep track of where each citizen is. Because of this, he will now only accept cash. The owner also tells Marcus that this very thing- the government keeping such close tabs on its citizens- is why he left Turkey and came to America.
I think why this passage stood out to me so much is because of the owner's motivation to come to America. We're supposed to be the land of the free and the home of the brave, yet we have to question if as American citizens we truly are free, and in this case, free from our own government. Obviously Doctorow takes these questions to a new level in his novel Little Brother with the heightened invasions of citizens' privacy, but he bases this future off of what is currently present in society.
Besides questioning Americans' freedom, this passage stood out to me because it was inspiring to see the owner decide to put the sanctity of his patrons' securities in his own hands. He made the decision to not accept debt cards anymore because he is trying to protect his customers, even if that means losing some customers due to the inconvenience. I thought this was extremely admirable and inspiring, considering he is trying to protect the very thing that drew him to America from Turkey.

Every Security Measure Has a Weakness

One of the things which stood out to me throughout the book Little Brother was how it was so easy for even everyday people to foil the security measures put in place by the Department of Homeland Security. One of my personal favorites was the "arphid cloners" which could replace all of the electronic information on things such as your credit cards and identification and replace that with those of someone else. A particular passage showcasing this was when Marcus' father came home after being pulled over and questioned twice. This occurred because his father had been all over town recently to many various places, or so the DHS thought from their surveillance data. His father really had done nothing wrong, but various people who had been "given" his identity were making it look like he had very odd travel patterns. This marked a turning point in the novel as Marcus' father finally realized that there were some potential downsides to all of this surveillance the DHS was performing.

This concept of messing with security goes far beyond this one specific type of exploit, and goes further than the book as well. Every method of surveillance must have some weakness, whether that be an ability to avoid it or to attack it with so much information it cannot sort through it all properly. That raises the question of how useful every surveillance implement of the government is in the real world. It is possible that any day a random group of people could come up with a method to completely mess with some form of NSA surveillance. However as seen in the book, it is us as citizens who are the ones that are punished when there are flaws in surveillance systems. Thus we must ask ourselves if we are truly comfortable continuing to give up some of our privacy to groups such as the NSA and if that our relinquishing some of our right to privacy is actually helping in any way at all.

The Paradox of a False Positive

As I was reading Little Brother, there was actually a passage that made me stop reading and reread and think about it for a while. This really never happens to me so I figured it was something I should take note of. This was the passage that talked about the paradox of a false positive. What this means is that if you are testing for something very rare in a sample population, like terrorists or people who have contracted Super AIDS, as the book says, then the test accuracy must match the rarity of whatever the case you're trying to look at. This reminded me of when we looked at the idea of data mining students to search for potential of suicide or mass shootings and the like. At the time, we simply talked about the ethics of looking into a students private data, but the efficiency and accuracy is a huge part of this too. Many college students at times will feel depressed or overwhelmed, and may search things that could potential be a red flag for the data mining for suicide. Similarly, I think a lot of people, myself included, are sometimes just curious about weird things that could seem like a red flag for mass violence, like how to make a bomb and stuff like that. If the schools took the time to look into all students that raised a red flag for suspicious behavior, they would be wasting so much of their time, and they could potentially miss real risks because of their focus on these non-risky individuals.

Taking control

In chapter 4 of Little Brother, there’s a passage where Marcus talks about the idea of privacy. He says that it is a feeling of liberation when you have an aspect of your life that is completely under your control. He compares it to things that we all do that are not shameful but would still require privacy. This passage struck out to me because it made me look at the whole online privacy issue in a new light. It made me consider the psychological implications of online privacy. Doctorow  brings up a great point through Marcus’s voice: For some people, online privacy is not just important because they have something to hide, it is a way to take control of their lives. I never considered this psychological angle to it, but with all of our lives being invested in the online world, it can seem easy to lost control especially considering how fast technology progresses. As humans we are inclined to creating organized systems and keeping things under control. So it makes sense that some of us would be cautious about oversharing our information online. It is very likely that people would feel a sense of vulnerability by having their information online and not feeling like they can keep up with it. Having this privacy can give people the sense of control they need so it doesn’t get too overwhelming.

 

Privacy: From Times Square to the Percent Accuracy

The overwhelming theme of the novel Little Brother concerns the privacy of an individual and a society in all aspects of life. From the moment in which Marcus is first questioned by the National Homeland Security (NHS) until the end of the novel, Marcus highlights to the reader of the many horrifying consequences of a government overstepping its boundaries. Two examples described by Marcus hit me hard about why privacy is vital in having a normal and functioning society.

The first example is after the NHS confiscates Marcus's electronic devices and receiving the passwords of those devices through brute force and intimidation. The NHS tells Marcus that if he truly has nothing to hide, then it should be no problem for them to take a look through his devices. This bothers Marcus extremely; however, he eventually gives in due to the fact that he knows that giving the NHS what they want is the only way for him to be released. Marcus compares this thinking of the NHS to forcing somebody to go to the bathroom in a clear glass room in the middle of Times Square. Although they have nothing to hide or protect, any normal person would want privacy when going to the bathroom and to not be in the public eye. This comparison was powerful in the imagery it invokes. Picturing somebody having to use the bathroom in public shows that Marcus having to give away all of his privacy and dignity is wasteful.

Secondly, as somebody who loves statistics and numbers in general, I also found the example of "false positives" and "percent accuracy" powerful. It demonstrates how problematic and inefficient the search and interrogation of almost everybody throughout San Francisco is in finding the terrorists who blew up the bridge. By displaying that even a 99% accuracy causes the government agencies and police to searching thousands and thousands of people further highlights the inefficiency of investigating people for possible terrorist suspects because in reality, their percent accuracy is closer to 50%. This example shows the reader not only how difficult it is to catch a terrorist in this manner, but also how it complicates and hurts the lives of the everyday citizens.

 

Statistically Suspicious

Corey Doctorow's novel Little Brother is a rousing look at a society where security has become dominant over privacy and liberty. In the aftermath of a terrorist attack on San Francisco, Marcus Yallow sparks and leads an underground movement to take back the rights of citizens from an oppressive police-state government.

I've read Little Brother before, but the issues and solutions regarding online security always fascinate me. The problem of the increased levels of encrypted traffic standing out particularly interested me. In the novel's universe, an agent monitoring web traffic and noticing a large amount of encrypted information passing to a single machine compared to the relatively larger number of people with unencrypted data would have his or her suspicion aroused. In some investigations, you don't need to know what someone is hiding, only that they are hiding something. However, this also brings to mind the possibility that a large amount of encrypted traffic from a computer doesn't always imply that illegal activity is occurring. Just as walking down the street with your hands in your coat pockets doesn't imply you're hiding drugs, stolen goods, or a weapon.

A statistically significant outlier might be an individual with malicious intent. But it also might just be one errant but innocent data point. The beginning of chapter 8 mentions the histograms and Bayesian analysis being used to find abnormal behavior. These were "not guilty people, but people with secrets." Privacy and the ability to keep some aspects of one's life out of the public eye are pretty much inalienable natural rights. Secrecy is an integral part of keeping ourselves normal, so it makes no sense to see a desire for privacy as statistically abnormal.

Abolishing the Government: Terrorism, or Activism?

Of all the themes hit upon in this novel, one of the ones that intrigued me the most was that of the rights of American citizens to alter or abolish our government. In a passage from Chapter 11, Marcus’s teacher, Ms. Galvez, leads a discussion on social movements in the past and present. While some of the movements she describes were peaceful or just full of pranksters, she also described the more violent or illegal actions taken by some protesters. Theft took place, and some protesters even blew up buildings. Throughout the discussions, Charles continues to insist that these people, regardless of motives or methods, are all terrorists. However, Marcus brings up an interesting point; he cites the Declaration of Independence, which states that “that whenever any form of government becomes destructive of these ends, it is the right of the people to alter or abolish it, and to institute new government…” (p.180). Essentially, the book is introducing an interesting argument; when are acts considered terrorism, and when are they considered a method to alter our government?

In my opinion, terrorists aim to cause fear. They destroy buildings and cause violence to try to strike fear into the hearts of people who live in a certain country, or worship a certain way, or hold a certain opinion. The acts they are taking might be an attempt to alter the government, but it is done in a way that is completely unacceptable and malicious. However, most protesters are out there because they believe there needs to be a change to the way our country works and they believe they need to speak up about it. They are out there because they believe that they have a duty to change a government that is not serving them. So if they are out there with this intent, why do authorities so often try to stop them? When the Declaration of Independence was issued, America acted on their words of abolishing a government by fighting a war. Today, though, social and political movements are being shut down for far, far less than engaging in warfare. Many movements are shut down simply because they are challenging the status quo in a way that is not deemed appropriate by local authorities. A prime example of this is the protests happening in Ferguson, MO. Even if protesters are engaging in civil disobedience, don’t they have a right to attempt to inspire change in their own government? In the Gettysburg Address, Lincoln stated that America was a “government by the people, for the people”. However, now it seems that some believe our government is so important that the people can no longer change it. Basically, we are calling some of our citizen’s terrorists when all that they are doing is trying to change a system that was supposed to work for them in the first place.

Security and Privacy

In the thirteenth chapter, the students talk about a question that "Under what circumstances should the federal government be prepared to suspend the Bill of Rights?" What they are talking exactly, in other words, is that should government suspend the Bill of Rights at extreme environments. This is a classic question in the works about the against between weak people and strong government. In the book "1984" and the movie "V for Vendetta" show us a picture of the terrific future when the government has huge power and ignores the rights of individuals. In fact, I thought the answer to this question depends on the side people choose. In the book, the author describes a teacher, Mr Anderson, who the reader might think her as a stubborn supporter of the government. In other hand, Marcus and his friends are the firm fighter for freedom. Some people might thought the privacy is much better than the security and some support the opposite opinion. I'm in the middle. I agree that the privacy of individual is very important, but I also think it's reasonable to sacrifice the privacy to make sure the security. Some people might point out that the government could grab the rights of people with this reason. I had to say any extreme is bad. The key point is to get the balance between the two side.

The Failure of Trust Itself

As I was reading Little Brother, I was intrigued by the points that Cory Doctorow made. Some of his arguments were interesting since Marcus was purely intent that the DHS was terrible. It seemed that the US would turn into chaos from the inside out because of another terrorist attack. We do not actually see the adult side. Without Marcus, the tactics the DHS was using to track down terrorists would have definitely been more efficient. The jailing teenagers’ part was a little extreme, but the other tactics such as following unusual routes could prove to be useful in tracking drug deals and even potential terrorist attacks.

That is not what intrigued me the most. The most interesting part of the book for me came at the beginning of chapter 10. This is where I finally understood how public/private key encryption works. We mentioned it a few times in class, but the beginning of chapter 10 explains the logistics of it. Using only public key encryption is useless because it is not a secret. Anyone on the web will be able to read the messages you encrypt. However, using both a public and private key is a very secure means of communication. The message is encrypted twice, both with a public key and a private key. There is still a very sneaky way of bypassing this. Billy could trick Bob, who is trying to send a message to Jim, into thinking that Billy’s public key is actually Bob’s public key. In this way, Billy can intercept Jim’s messages and become a man in the middle. In order to actually maintain secrecy, one must establish a web of trusts. But even this web of trusts can be infiltrated, as evidenced by the events later in the novel. That is the inherent flaw in the private/public key encryption. It involves around human trust, which can be easily betrayed by anything from money to power. Human trust is what fails here in the situation provided in Cory Doctorow's novel.

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