Why Crypto?

As any self-respecting writeup should do, this post is going to explain what cryptography is all about and why it is important.

So to answer the first question, let’s look at the definition of a seemingly unrelated word:

System: a set of principles or procedures according to which something is done; an organized scheme or method.

I got that off of Merriam Webster. But why is that important now?

Well, what you need to recognize is that most of what you see around you is indeed a system. You getting the newspaper every morning?

That’s a system. The paper has to get printed in the newspaper office, given to a delivery person, who then has to get on some mode of transport to come to your address, and then get to your address and hand it over to you (or like in the picture above, throw it over).

Let’s look closer at this scenario. If there is some problem in any of the steps, you don’t get your newspaper. For example, if the printing press suddenly stops working, then the newspaper doesn’t get printed. Or if there is no vehicle left for the delivery person to get to your house, you don’t get it. Again, if you have provided the wrong address, the newspaper will be delivered to some other destination.

I think it’s fair to say this sort of analysis is what engineering is all about. The study of how to build robust systems. To do that, you’re going to have to look for vulnerabilities. It’s a basic principle of engineering that every system in nature is going to have some flaw. What we have to do is minimize flaws or at least make them really hard to use against you.

This is especially important because there are people who are looking for flaws to exploit. Going back to the newspaper example, you could have a miserly neighbour who doesn’t want to pay for his own newspaper. So what this guy does is register his own address under your name. Thus you don’t get the paper but have to pay for it. An exceptionally poor newspaper delivery system would allow for such flaws. That’s why there are people who look after the system to make sure this doesn’t happen.

Now how does this relate to cryptography?

Well, even sending a message to another person involves systems! Let it be an ‘exercise to the reader’ to figure out the steps for sending a message ;)

Suppose you don’t want someone to see your message though. Then it’s going to be a problem to just write and send a letter. Because a person can just intercept your message and open the envelope to read it.

So you’re going to have to disguise your message in some way. And then there’s going to be someone smart who will look for a vulnerability in what you do and exploit it. And then you’re going to have to be smarter to hide it better. Then someone even smarter comes along to find out another vulnerability to exploit. And ad infinitum.

How you can hide your message is what cryptography is all about, and finding better ways to do that is what cryptographers do. You’re going to learn about those in subsequent posts.