The History and Mathematics of Codes and Code Breaking

Month: October 2012 Page 2 of 3

Oh What a Tangled Web

A Tricky Web of Trust

The passage in Little Brother that really intrigued me was the passage about “a web of trust” found on pages 153 and 154. The previous passage talked about public keys versus private keys and the risks associated with these keys. It is very difficult to make the public key incredibly public and a middle man can easily confuse the two people trying to communicate by secretly intercepting, reading and changing messages. The only way to ensure that communication is secure is to meet in person and swap keys, thus creating a secure web of trust limited by the pure number of people you can meet up with in person. However, if people keep passing on all of their keys to people they trust the ring grows and encompasses a larger group where secure communication is possible.

I think this is incredibly interesting since it seems then that any terrorist or criminal group would use this to communicate. Most partners in crime meet in person and would be able to devise such a plan to evade any potential middle men trying to intercept their communications. The passage seems to say that if you trust someone enough and see him or her in person, you can absolutely ensure safe communication with him or her. This ties into our discussions on whether the cryptographers or decrypters are winning and if such strong cryptos should even be allowed. In this case, the passage seems to be claiming that cryptographers will always win if they employ this strategy. This leads to questioning whether these encrypted messages are truly protecting innocent people or if they are masking and hiding criminals and terrorists. The argument could beOh What a Tangled Web made that cryptography that is unbreakable unless trust is broken is considered too strong and can be used too easily for harm. While this cryptography method may be used to protect individual’s privacy, I assume it would also be used to enable dangerous communication and activity.


Image: Oh What a Tangled Web by Jenny Downing, Flickr (CC)

Privacy: The True Meaning

In Chapter 4 of Little Brother, Doctorow gives a great definition and explanation of what privacy is and how it is sometimes construed in the modern age when he relates keeping information private and going to the bathroom. He explains that there is not anything inherently wrong, weird, or shameful about going to the bathroom, but that everyone would be hesitant about doing it in public with hundreds of people watching. Of course we would all agree with this, so then why is it wrong to keep some things we do on the internet private? The answer that Doctorow wants to get across is that it is not wrong at all, “it’s about your life belonging to you.”

The reason this particular passage stood out to me the most was because I have always agreed that you should be allowed to keep certain things private on the internet without it being considered weird or wrong, but I never could really come up with a really good reason why. When I read this part of the novel, I was frankly kind of amazed. An analogy that seems so far-fetched at first glance, worked perfectly to explain how I feel about privacy on the Internet. That particular passage was so well done and relatable that after reading it I found myself being much more empathetic towards Marcus as the novel progressed.

Image: “Please!,” by Josh Hallett, Flickr (CC)

Unsolved Mysteries Resources

And some resources from our class on unsolved mysteries last week…

Babbage and Lovelace Resources

As promised, some links about Charles Babbage and Ada Lovelace…

And here’s my Prezi showing Babbage’s technique for breaking the Vigenere cipher.

Illegal Cryptography is Illegal Mathematics

The excerpt in Doctorow’s Little Brother that caught my attention the most and interested me was the very beginning of Chapter 17. Mathematics is an integral part of our society and the technological advances behind its development. Also, isn’t Cryptography just another application of math? So when Doctorow explained that the “government classed crypto as a munition and made it illegal for anyone to export or use it on national security grounds,” it jumped out to me how ridiculous this statement was. The thought of having “illegal math” is like throwing people in jail because they were thinking creatively. The NSA has a standard maximum strength cipher and no one was allowed to create a cipher stronger than that standard. When a graduate student may have created a possible cipher in a paper, the NSA decided to ban the publishing of this paper. Reading about this in Little Brother made me realize the extent of our freedom of expression nowadays. If these crypto wars in the 19th century continued and the government prevailed, then modern advancements in technology would have never have even happened. I believe that we depend more on free cryptography than we may realize because it spawns innovative thinking and creations.

The Power of Publicity


In Cory Doctorow’s Little Brother, the author examines the boundaries of invasion of privacy in today’s society. As the main character, Marcus, and his friends fight against the  U.S. Department of Homeland Security’s intense surveillance of all citizens following an astronomical terrorist attack, they must establish methods for communicating without their messages being interrupted by the DHS, whose head members are scrambling to accumulate evidence that Winston took part in planning the attack. 

In chapter six of Doctorow’s social criticism, Marcus explains that he will need to encrypt his messages to avoid the prying eyes of the government. In his brief discussion of cryptography and its effectiveness, Marcus makes a startling affirmation. “You have to publish a cipher to know that it works,” he claims. While this idea initially seems to violate the idea of cryptography, encoding messages to keep the content safe from being revealed to anyone but the intended receiver, after some thought Marcus’s bold statement reveals his true wisdom. He explains that while he could create his own cipher, he would never know if it was secure from others because he had created it himself without first testing its security. Contrary to “anyone” who can create their own cipher system that to them is unbreakable, Marcus suggests first publicizing said cipher system before use. This method would release one’s code into cyber space or print, encouraging others to attempt to crack it. Marcus concludes his argument by simply stating that in today’s society, you do not simply create your own cipher and assume it is secure; rather, he emphasizes using “stuff” that has been around forever, but has never been successfully cracked.

I initially found Marcus’s assertion that publicizing one’s cipher was the ultimate way to ensure security to be naive, but with further examination found it to be most insightful. Initially publishing the cipher you created to see if others could indeed break it seems silly. You would not be able to utilize the cipher if it is released and then cracked, and simply utilizing the cipher without checking its security could be more efficient; however, if you publish your cipher for everyone to see, and encourage others to break it, you are utilizing the most valuable source for ensuring its security. Ultimately, having an insecure cipher is more detrimental than losing speediness while searching for an effective cipher.

Image: In The News by paurian, Flickr (CC)

Looks Guilty, is Guilty

The brutal treatment of the protagonist, Marcus Yarrow, in Chapters 3 and 4, following the Bay Bridge bombing was something that suck out to me as I tried to put myself in the situation and how I would have reacted.  One less obvious theme related to cryptography which I noticed was the appearance of guilt that results from Marcus’ heavy defense of his privacy.  It is human nature to feel that someone who does not want to tell you everything would be hiding something bad from you.  Marcus’ actions in his first encounter with the Department of Homeland Security’s interrogation seemed to point to him trying to hide something.  Although Marcus only tried to resist for a short amount of time, and the treatment by the Department of Homeland Security was less than proper, he did show resistance which could have prompted some reaction by the DHS.

The concept of no cipher being better than a bad cipher was also present in this scene.  The idea of this is that a ciphered message which is broken could do more harm to the party enciphering than if the same message was discovered not enciphered.  Although there were no ciphers, the passwords and security precautions made by Marcus made him look guiltier just as an enciphered message could have done.  In this scene the passwords were not “broken” but instead were taken by force, which in the long run, has the same overall effect. Regardless of the means of discovering a secret, the fact that it was a secret makes it seem worse to the party discovering it.

Image: This is Secret by Trey Ratcliff

Severity Overlooked

In chapter 5, Marcus is released from prison and he returns to his home. He starts up his self-constructed laptop and realizes that something is wrong with it after the power cord refuses to stay connected. He now realizes that the entire casing of the computer was no longer aligned properly. After his parents go to sleep, Marcus rises from his bed and makes room on his desk for his laptop. He removed the outer casing and realized that the keyboard and logic-board weren’t connected properly. When Marcus looked more closely, he realized that there was something underneath the cord. It was then that he realized that his computer had been bugged. Doctorow then describes Marcus’ overwhelming anxiety and paranoia taking over. This scene stood out to me because I recently wrote a paper on data mining in which I firmly presented my opinion that privacy should be completely discarded in order to maintain security. The panic that ensues Marcus’ discovery completely opened my eyes to the seriousness of an individual’s right to privacy. Clearly I was biased in the past in that I never dealt with a violation of my rights to the degree that Marcus had to endure. Marcus states, “I’d been feeling paranoid when I got home. Now I was nearly out of my skin. It felt like I was back in jail…”. This comparison between a violation of privacy and jail depicts the seriousness of the situation.

We Don’t Know What We Have Until It’s Gone

Chapter 4 of Little Brother circles around the idea of a want for familiarity. After the main character, Marcus Yarrow, is taken hostage, he is stripped of his belongings and dignity. Marcus talks about wanting to be back with his friends and parents, as anyone would in this situation, but what intrigues me is how much we all take such familiarities for granted. As Marcus realizes he is getting onto a boat and leaving his homeland, he becomes sick to his stomach at the thought of never seeing his parents again. However, had Marcus been leaving to go on a vacation without his parents, he most likely wouldn’t have thought twice about parting with his parents. On a similar note, seeing a pizza carton’s familiar logo causes Marcus to be sad and nostalgic of his free life. Yet before taken hostage, the pizza logo was virtually meaningless. This chapter has made me realize that we take so many things for granted and don’t realize what we have until its gone. Marcus even stated that he missed his school, which he couldn’t have hated more in the first few chapters. Aside from parents and friends, we also don’t realize the freedoms we as American citizens have, and all take for granted. At the end of the chapter, Marcus is finally released and couldn’t be happier have his usual clothes back and hear the familiar sounds, which went unnoticed before this event, in his familiar city. Marcus now appreciates these feelings and items that used to be overlooked. 

Emotion vs. Logic: The Web of Trust

In Cory Doctorow’s novel, Little Brother, the protagonist Marcus Yallow and his comrades form a web of trust as a response to the DHS’s infiltration of the Xnet. The concept of a web of trust intrigued me. As a product of cryptography, the web of trust relies heavily on the actual trust between individuals and less so on the complexity of the cipher. The biggest weakness of the web of trust is not that the cipher can be broken, but that the people involved may be untrustworthy. In addition, one untrustworthy person can compromise the entire web because each person holds the others’ keys.  The danger of the web of trust is illustrated with Masha’s threat that she can compromise the whole web of trust because she is a part of it.

Another aspect of the web of trust that I found interesting was that it required the participants to meet in person. Although it reduces the convenience and accessibility of the web of trust, it greatly increases its security. As mentioned in the novel, public-key cryptography is vulnerable to the man-in-the-middle (in Marcus’s case, the DHS) and could result in the unknown interception and decryption of incriminating messages. With the web of trust, only those in the web have access to the public keys, and therefore all the messages received by others from the web are guaranteed to be legitimate.

The logic and encryption behind the web of trust is invincible to decryption. The intelligence of a cryptanalyst is irrelevant to breaking a web of trust; in fact, exploiting the instability of human relationships is the only method in which the web can be broken. Because the web’s security relies on human emotion and the trust between individuals, it could actually be potentially weaker than other forms of cryptography. The fickle nature of trust formed between friends and colleagues is a risk that could possibly equal the mathematical vulnerability of other ciphers.

Image: “wide web,” by josef.stuefer, Flickr (CC)

Page 2 of 3

Powered by WordPress & Theme by Anders Norén