Archive by Author | Kartik Cating-Subramanian

Ciphers: Hiding in Plain Sight

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My last post talked about cryptography, its motivation and its primitive techniques.  In this post, we shall learn about modern security techniques and how they keep us secure.  We will touch upon the mathematical basis behind modern cryptography, talk about symmetric key cryptography and talk about a technique for exchanging secrets out in the open known as the Diffie-Hellman key exchange.  To start off the discussion, I would like you to consider the following situation.  Alice is a diplomat in a foreign country and has some sensitive information that she would like to communicate to Bob, her superior.  The only means of communication available to Alice is a phone line that she and Bob knows is constantly being monitored and eves dropped on.  How could Alice and Bob communicate a message in a secure manner starting from this state?  We saw in the last post how, with some pre-decided shared secret (such as a codebook when using a substitution cipher), one could attempt to obscure a message and make it hard (but not too hard) to guess.  More curiously, starting with no secret state between the two parties, is it possible to establish a secret codebook?  In other words, sharing no secrets beforehand, is it possible to begin sharing a secret?

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Ciphers: Early Techniques

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We have all heard the word ‘encrypted’ used many times on television or in movies.  It is usually implies some form of security or an obstacle that needs to be overcome by some button pushing by a man in a lab coat.  Shows such as CSI and Law and Order use it, almost indiscriminately and often inaccurately.  So what exactly is encryption and what does it mean to say that a message is encrypted?  In this post, I shall describe the motivation behind cryptography, a number of early encryption schemes and the idea behind modern cryptography. In the second post in this series, I will describe more modern algorithms as they are used today in computers to protect your identity, privacy and security on the Internet.
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What’s cooking?

An incandescent light bulb

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Ever wondered how an electric incandescent bulb, an electric room heater or an electric stove worked?  Ever wondered how they produce so much heat and light?  Today, we will explore the working of electric bulbs and heaters.  I will given an overview of how electric power is converted to heat and light.  As a bonus, here is a quick poll to give you a teaser.

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A Fowl Dilemma

Which Came First, The Chicken or The Egg?

Image by "The Wanderer's Eye" via Flickr

Today, I will tackle the conundrum of Which came first:  the chicken or the egg? This is an age-old dilemma, confounding early philosophers.  The core argument takes the form of a catch-22.  All chicken hatch from an egg.  Hence, to have a chicken, one must first have had an egg.  But chicken eggs need to be laid by a chicken.  Hence, to have an egg, one must first have a chicken to lay it.  Phrased this way, this question does not seem to have a good solution.  Nevertheless, evolutionary biology has been able to resolve the issue with a correct but perhaps unsatisfactory answer.


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The Eternal Fall

Here is a video of some astronauts on the International Space Station (ISS).  It depicts some common (and uncommon) activities that they do aboard it.  It has background music – so turn down your volume if you are at work.

As you can see, astronauts in space operate in a ‘zero-gravity’ environment.  They float around effortlessly and don’t fall toward the ‘floor’ of the space station.  Water, in a space station such as the ISS, automatically assumes the shape of a ball and floats around.  This is indeed, quite a strange environment.  But have you ever stopped and wondered – why are the astronauts actually floating?  Is it because there is no gravity in outer space?  Is it because the earth’s pull is so weak that it no longer affects them?  Is it because they are constantly being pushed away from the earth by rockets?  Or is it something more subtle?  In this post, we shall explore the phenomenon of micro-gravity.

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Three Strokes and Out

In this post, I will discuss the working of a four stroke internal combustion engine such as the one used in most automobiles.  The engine of most modern cars runs on gasoline/petrol.  It does this by burning petrol in air and using the energy of the hot gaseous by-products to produce mechanical movement and motion of the car.  We shall explore how fuel and air are combined in the engine, how the controlled explosion is initiated and how all the heat is converted into rotational energy for the wheels.

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The Day The Earth Stood Still

Earth

What would it take to make the earth stop spinning?  This scenario is not unheard of in B-movies and bad sci-fi shows.  It isn’t uncommon to have plots involving the Earth’s core slowing down or aliens from a different galaxy stopping the Earth’s rotation.  A lot of these plots have the Earth stop spinning either instantaneously or within a very short period of time.  Intuitively, we know that spinning bodies have energy.  The Earth is a pretty massive spinning body.  How much energy would the Earth have to shed to stop rotating?  How would that energy affect us worldly inhabitants?

Here, I will discuss the physics behind rotation and rotational energy.  We shall use simple facts about the Earth’s rotation to calculate what would happen to it were it to stop spinning.

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