Archive | January 2011

An Offer You Cannot Refuse

Currency - by bradipo

Imagine that you are on a game show.  Consider the following two scenarios:

The host has given you $2000 to begin with.  You are now given a choice – you can stay with your money or participate in the “Double or Nothing”.  Should you choose the event, the host would flip a fair coin.  Should the coin land heads, you will get an extra $2000.  Should it land tails, you lose the $2000 you have.

The host has given you $4000 to begin with.  You are now given a choice – you can participate pay a fine of $2000 or participate in the “Trap of Doom” event.  Should you choose the event, the host would flip a fair coin.  Should the coin land heads, you get to keep all $4000.  Should it land tails, you loose all $4000 to the “Trap of Doom”.

Would you participate in the “Double or Nothing” event?  Would you participate in the “Trap of Doom”?  Are your answers different?

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Ciphers: Hiding in Plain Sight

Icon from Nuvola icon theme for KDE 3.x.

Image via Wikipedia

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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United We Stand: The Tale of a Polymer

What is a polymer?

Polymers are all around us. They are in our cars, they are in our adhesives, they are in our food, and they are in our bodies. Plastics, rubbers, glues, starches, and even DNA are all polymers. What could all of these things possibly have in common? The answer lies in the name. Polymer is a word stemming from the Greek words for many, poly, and parts, meros. A polymer is simply a molecule which is made up of many parts. These parts, called monomers, are often many repetitions of only one or two molecules, though it is conceivable that a polymer in which every monomer differs from every other can be produced.

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