About Prateek Joshi

I want the machines to see the world ... see the world the way I see it!

Elliptic Curve Cryptography: Part 4/4 – How Do We Use Elliptic Curves?

1 mainIn the previous blog post, we discussed about elliptic curves and saw what they look like. We also looked at some of their special properties that enable it to be a good trapdoor function. But this is still very mathematical, right? The curves are great to look at and we understand general concept of elliptic curves, but how do we use them in real life? The curves denoted by those equations don’t represent the curves that are used in cryptography. In the real world, things are digitized. We need to convert things into bits and move them around quickly. So how do we do it?   Continue reading

Elliptic Curve Cryptography: Part 3/4 – What Is An Elliptic Curve?

1 mainIn the previous blog post, we discussed why RSA will not be sufficient anymore. We looked at how machines are getting stronger, and that we cannot rely on factorization as our primary mathematical foundation. We also talked a bit about what we are looking for in our new system, and then said a quick hello to elliptic curves. In this blog post, we will see what elliptic curves are. As always, we will keep the equations to a minimum, and instead, try to understand the underlying concept. Let’s go ahead, shall we?   Continue reading

Elliptic Curve Cryptography: Part 2/4 – Why Do We Need It?

1 mainIn our previous blog post, we discussed public key cryptography and how it works in general. The RSA is so powerful because it comes with rigorous mathematical proofs of security. The authors basically proved that breaking the system is equivalent to solving a very difficult mathematical problem. When we say “difficult”, what it means is that it would take trillions of years to break it even if all the supercomputers in the world were to work in parallel. By the way, this is just one encoded message! The problem in question here is prime number factorization. It is a very well-known problem and has been studied for a very long time. So if it’s such a difficult problem, why do we need something new? What’s the problem here?   Continue reading

Elliptic Curve Cryptography: Part 1/4 – Why Should We Talk About It?

1 mainElliptic curve cryptography is one of the most powerful techniques used in the field of modern cryptography. Just to be clear, elliptic curves have nothing to do with ellipses. I agree that the name can be slightly misleading, but once we discuss what elliptic curves are, it will become much clearer. So as you may have already guessed, elliptic curve cryptography (ECC) is based on the properties of elliptic curves. ECC is very useful in internet security and it is being deemed as the successor to the almighty RSA crypto system. If that didn’t make sense to you, don’t worry! We are going to discuss everything in detail. A lot of of websites are increasingly using ECC to secure everything like customer data, connections, passing data between data centers, etc. So what makes ECC so special? Is it strong enough to take over the world?   Continue reading

What’s The Use Of Function Pointers In C++?

1 mainWhen we talk about C++ programming, functions and pointers are very important. A function is basically a series of steps packaged into a nice unit. A pointer is an object that refers to a value stored in memory. So why not just combine them and create something really useful! Function pointer is exactly what you think it is. A function pointer is a variable that stores the address of a function. We can call this function using the function pointer. But why would we want to do that? This looks like a roundabout way of doing things, right? What’s the purpose of having it in the first place?   Continue reading

What Is A Markov Chain?

1 mainIf you have studied probability theory, then you must have heard Markov’s name. When we study probability and statistics, we tend to deal with independent trials. What this means is that if you conduct an experiment a lot of times, we assume that the outcome of one trial doesn’t influence the outcome of the next trial. For example, let’s say you are tossing a coin. If you toss the coin 5 times, you are bound to get either heads or tails with equal probability. If the outcome of the first toss is heads, it doesn’t tell us anything about the next trial. But what if we are dealing with a situation where this assumption is not true? If we are dealing with something like estimating the weather, we cannot assume that today’s weather is not affected by what happened yesterday. If we go ahead with the independence assumption here, we are bound to get wrong results. How do we formulate this kind of model?   Continue reading

What Is Manifold Learning?

1 mainMachine learning is being used extensively in fields like computer vision, natural language processing, and data mining. In many modern applications that are being built, we usually derive a classifier or a model from an extremely large data set. The accuracy of the training algorithms is directly proportional to the amount of data we have. So most modern data sets often consist of a large number of examples, each of which is made up of many features. Having access to a lot of examples is very useful in extracting a good model from the data, but managing a large number of features is usually a burden to our algorithm. The thing is that some of these features may be irrelevant, so it’s important to make sure the final model doesn’t get affected by this. If the feature sets are complex, then our algorithm will be slowed down and it will be very difficult to find the global optimum. Given this situation, a good way to approach it would be to reduce the number of features we have. But if we do that in a careless manner, we might end up losing information. We want to reduce the number of features while retaining the maximum amount of information. Now what does it have to with manifold learning? Why do we care about reducing the dimensionality of our data?   Continue reading

The Concept Of Homogeneous Coordinates

1 mainPeople in computer vision and graphics deal with homogeneous coordinates on a very regular basis. They are actually a nice extension of standard three dimensional vectors and allow us to simplify various transforms and their computations. When I say “transformations”, I am talking about all those special effects on the screen, and the corresponding movements and scaling of various objects. But why do we need homogeneous coordinates to do all that? Why can’t we just move the objects around? Well, we can’t directly do that, not easily anyway! This will become clear soon. The concept of homogeneous coordinates is fundamental when we talk about cameras. In order to design our algorithms, we need to understand how the cameras are looking at the real world. This is in fact utilized heavily by game programmers as well. So what is it all about? Why is it so important?   Continue reading

What Is Maximum Likelihood Estimation?

1 mainLet’s say you are trying to estimate the height of a group of people somewhere. If the group is small enough, you can just measure all of them and be done with it. But in real life, the groups are pretty large and you cannot measure each and every person. So we end up having a model which will estimate the height of a person. For example, if you are surveying a group of professional basketball players, you may have a model which will be centered around 6’7″ with a variance of a couple of inches. But how do we get this model in the first place? How do we know if this model is accurate enough to fit the entire group?   Continue reading

Using Hash Function In C++ For User-Defined Classes

mainIf you are a programmer, you must have heard the term “hash function”. In its most general form, a hash function projects a value from a set with many members to a value from a set with a fixed number of members. We basically convert the input into a different form by applying a transformation function. Hash functions map data of arbitrary length to data of a fixed length. The values returned by a hash function are called hash values. An interesting thing to note is that hash functions are not reversible. This means that you cannot recover the original data from hashed values. This property makes it one of the most useful data structures known to mankind. Hash functions are used extensively in internet security. In this post, we will talk about C++ STL and how to use hash functions with user defined classes.   Continue reading