Someone I know is currently involved in a project associated with acquisition, transfer, storing, and processing confidential data. As I have an experience with IT security, I was asked about which encryption method suits the problem the best. When I listened carefully to the problem, I asked to clarify: “Do you really need encryption? Or password should be sufficient?”

What are the difference between cryptography and password protection anyway? The following is the illustration contrasting those two. Imagine that you have a secret document that you do not want others but few number of people to read. If you put it in a box and put a padlock to seal the box, that’s password protection. If you on the other hand, translate the document into codes that only you and few others can read and then burn the original document, then that is encryption.

The next question would be: which one is safer? Is one method more secure than the other? I would say that depends on the necessity, though generally speaking encryption is the safer method. However if that makes you think it is always better to use encryption, then there are some aspects you should consider.

• For password, size of the documents should not matter that much. Basically it does not make any difference to the padlock if you put 5 pages or 50 pages of documents into the box. While for encryption, you will need more effort to code 50 pages rather than just 5 pages. Let us not forget the one who want to read the document will also have to translate all those 50 pages, especially if there are many parties to read those. This process is called decryption by the way.
• For data distributing, encryption should be safer. If you send a message in a locked box and then someone intentionally break that box and read your message, then you are done for. However if you are sending coded message, even when it is intercepted, the interceptor would not be able to read the message (assuming only the intended readers know the code that is).

There are also consideration of strong/weak password and strong/weak encryption, in analogy to strong/weak padlock and hard/easy code. In computer, stronger in both terms means more computational power needed.

As I learned the project requirement, I came up with this suggestion:

• For storage, as the data amount is enormous, strong encryption will make data reading and processing slower. Therefore, good password is better than choosing a half-good encryption for instance.
• For distribution, it turns out that the data has two parts: highly confidential (small size) and low confidentiality (large size). I recommended using encryption for the high confidential data and simply zip-password the other.

There are pros and cons of every method. By writing this, I hope this discussion can help you understand which method better suits which need. In my friend’s case, the above discussion was proven to be exceptionally handy. Just saying B-)

# A Combinatorics Problem

Let $1,2,3,...,n$ be an ascending sequence of number. If swapping the $i^{th}$ and ${i+1}^{th}$ position is considered as one step for $i \in \{1,...,n-1\}$, then determine the least number of steps needed to reorder the sequence to be a descending one ($n,n-1,...,1$).  How can you be sure that your number is indeed the least number of steps?

P.S. Even though this problem looks like a toy problem, it definitely isn’t. This is a dumbing down version of a real problem I’ve solved in using a computer program before. I really saved a lot of time by solving this problem 😀

# Souvenirs from Bandung part 2 (and Bulgaria) :D

When I packed my bag to go to Bandung on Wednesday I only put in one shirt for Thursday although I planned to stay until Friday. I thought, “hey, it’s Bandung and I travel there to shop, why would I pack so many shirts? I should just go buy some”. I probably shouldn’t have oversimplified things. Though one of the reason I went to Bandung is to shop, my shopping time frame is pretty tight and sometimes I can be a bit picky. Thus, I fail to find even a single suitable shirt~ when the shirt match, the price doesn’t and vice versa 😆 Luckily I met my junior Oskar who gave me souvenirs from his short visit in Bulgaria for International Mathematics Competition. Why am I so lucky? Because one of the souvenir is T-shirt, yeaaay, problem solved 😉

Thank you so much Os 🙂 Here’s the photo of the souvenirs:

# Souvenirs from Bandung part 1 (MAC)

MAC, stands for Mathematics Aid Center, is a consultation room in Mathematics Study Program of ITB. If you’re an ITB student and have problems regarding Mathematics, especially problems from courses, you are welcomed to come and ask for assistance. I used to manage this room for a long time. Too long perhaps, for my name is clearly associated with MAC, as well as MAC’s name is associated to me 😆 Anyway, I had an opportunity to visit this nostalgic room yesterday, met the new coordinator, as well as some of the assistants.

The moment I stepped in, Akbar, an assistant in MAC and a good friend welcomed me by presenting his Master thesis problem right away. He clearly didn’t miss me that much, did he? 😀 Continue reading “Souvenirs from Bandung part 1 (MAC)”

# The barber that shaves all and only those who do not shave themselves

This is not a posting about shaving/barber.. but this may change your perspective about shaving.. forever. Okay I exaggerated, that’s only me I guess 😀 This is actually a posting about a logical puzzle and paradox, and no shaving experience is required to understand this paradox 😆 The antimony itself is the following:

Suppose there is this hypothetical village where all male citizens keep their face clean from hair by shaving. There’s only one barber there, and this barber shaves all and only those men who do not shave themselves. The question is, given that the barber is a male.. who shave the barber?

The only possible answer is.. the barber himself, of course. Since from the sentence “… this barber shaves all and only those men who do not shave themselves” we know that any man in the village is either shaved by himself or by the barber. So the barber can only be shaved by himself (the barber) or by the barber. However, is it true that the barber shave himself. Owh.. come on Hafiz, how often have I said to you that when you have eliminated the impossible, whatever remains, however improbable, must be the truth?
Continue reading “The barber that shaves all and only those who do not shave themselves”

You’re a mathematics student? Ever wondered who is the advisor of your advisor? Or are you interested in history of mathematicians? Then this website is for you.

The Mathematics Genealogy Project is a database project which mission is to compile information about all mathematicians in the world~or at least those who already received their Doctoral degree. In this website you can find the following info about a mathematician: Continue reading “Who’s (the daddy of) your daddy?”

# No sir.. we can’t get through the singularity (part 2)

Hahaha.. I finally get back to this topic after leaving it for more than a month. This posting is the sequel of this one which discussed the gravitational singularity of the sun. Anyway, as I wrote in the first post, that I write because I remembered a scene in a movie titled Sunshine. Coincidentally, the movie was aired on Global TV few days after the post published 😀 Also, about that first post, a friend asked me about the simplification into two dimensional model. My defense was that the particle will always move on a fixed plane around the sun. To see this you can compute the angular momentum $m(X \times V)$, where $X$ is the position vector and $V$ is the velocity vector. Then, you can compute the derivative, which is equal to 0. Thus, the angular momentum is constant and then the position vector lies on a fixed plane orthogonal to angular momentum 😉 Continue reading “No sir.. we can’t get through the singularity (part 2)”

# Unintended surprise

Last semester, I sat in graduate complex analysis class taught by Pak Wono Setya Budhi.. Thank you very much for letting me study inside your class sir 😀 Instead of only sitting in and hearing the lecture, I was also working on the assignments and participating in class discussion. But I chose not to attend both exams~the mid and the final. Some of you may know that I usually get out early from the exam room. One extreme case was when I went out after less than 30 minutes in an 120 minutes exam (I finished in 20 minutes and it would be extremely boring to wait for another 100 minutes inside :P). And I don’t wanna induce panic in this class where I was only sitting in~ha3x just kidding guys 😆

So I skipped the mid test, but in the next lecture hours I asked my classmate the questions and took a picture of it so I can work on them later. This morning I browsed through my gallery and stumbled on the picture

# No sir.. we can’t get through the singularity (part 1)

Few days ago I suddenly remembered a movie titled Sunshine that was released in 2007.. It was directed by Danny Boyle (Slumdog Millionaire) and there are many stars in the movie including Chris Evans, Cillian Murphy, Michelle Yeoh and so on. In the movie, for unexplained reason, sun, the nearest star to earth is dying. Therefore a group of scientists are sent to drop a nuclear bomb to sun to reignite it. It was a great movie by the way, but that’s not why I am writing this post.. I remembered a scene where the physicist (played by Cillian Murphy) cannot calculate the trajectory or speed (or whatever) because in his calculation sun plays the role of singularity..

From wikipedia, gravitational singularity is:

 “ A gravitational singularity or spacetime singularity is a location where the quantities that are used to measure the gravitational field become infinite in a way that does not depend on the coordinate system. ”

# What happen in MAC when you’re not around

You wanna know what we assistants do in MAC ITB when you (our clients) are not around. Here’s the video.. (dewa2 MAC beraksi)

If you’re a frequent visitor of MAC you may know better that this kind of thing is definitely not the only thing happen when our clients are not around 😆 Hopefully, we can see more of this happening in MAC in the future, even when I’m no longer around.

Disclaimer: No, I’m not in the video.. 😀

# The uneasy relationship

Some of you who know me personally may know that I had been working on a research project in Elliptic Curve Cryptography (ECC). This posting is discussing an article “The uneasy relationship between Mathematics and Cryptography”, from which this post got its name, published by the “Notices of the AMS” written by Neal Koblitz~the one who first proposed ECC. You can download this publication for free at AMS website, just google Notices of the AMS to get there. The first part of this article discussed how beneficial the cooperation between mathematicians and cryptographer. The second part examined the different expectations and culture clash that occurred  and became downsides in this cooperation. I will point out several of the latter in this writing.