Cryptography

Any peer-to-peer network (especially the ones we’re going to focus on for the next couple of articles) comes with a set of risks. The most concerning among them are: Confidentiality, integrity, non-repudiation, and authentication.

Let’s take for example a peer-to-peer network between A, B and C. Let’s suppose A wants to send a message to B that A doesn’t want anyone except B to see.

Here, since C is a part of the peer-to-peer network, it might see the message and the message would thus lose it’s confidentiality.

If C sees A’s message to B and modifies it before B receives it, there is an issue with the integrity of the message received by B.

Non-repudiation is the assurance that A cannot deny sending the message to B.

Authentication is the process that let’s B know that the message has in fact come from A and not someone else posing as A.

Well, this is where cryptography comes in and solves the aforementioned problems.

The word cryptography has two parts to it, ‘crypt’ which essentially means “hidden”, and ‘graphy’, which stands for “writing”. Thus, what cryptography does is, it converts your message into a code so that no one else can read it except the intented receiver of the message. The process of converting the message to a secret code, a.k.a, cipher text, that no one can make sense of is called encryption. To encrypt a message, you need two main parts- a cipher and a key.

Cipher is the set of rules that you’re using to encode information.

Key tells you how to arrange those rules (otherwise they would be the same every time and it’d be way to easy to decode the information).

The process of unravelling the code so that the recipient of the message can read the original message from the sender is called decryption.

The are two types of keys in cryptography, namely, symmetric key cryptography and asymmetric key cryptography. We will look into this in a future blog post.