Unlock the Secrets of Asymmetric Cryptography — With Private Key Indeed

Beginner´s Guide to Important Blockchain Concept

6 min readJul 6, 2022

I don’t fully understand blockchain and at this point, I’m too afraid to ask.

If this doesn’t apply to you, feel free to skip this and read other more technical pieces. This article even includes an image of a frog 🐸 and lego buildings 🏰, which should be a red flag for anyone more advanced in crypto technology.

I am not a crypto expert, but I know some graduate math which I’m going to utilize to explain the intuition behind blockchain technology.

The series are so far divided into two parts. (I am accepting any tips on what the topics of next parts should be about.)

Asymmetric cryptography — why is everyone mentioning something with private keys and elliptic curves?
Elliptic curves — what math they accommodate that is so amazing to be used for securing our money?

Now it’s time to bite the bullet.

So what is blockchain?

I heard someone asking if blockchain = bitcoin, or if blockchain is a scam. Imagine you are to write a definition of blockchain in one sentence — what do you say?

Similarly to punk, blockchain is not dead. 🎸🎶One of the most cited definitions says:

A blockchain is a growing list of records, called blocks, that are securely linked together using cryptography.
Source: [1]

I imagine blockchain like a thick virtual accounting book. 📖 This “book” contains a lot of info on who paid whom, who owns what etc. But you cannot just come and write into this “book” that you own a Big Ben or that I just sent you 1000 dollars.

You indeed need to prove it and that is where the cryptography comes to the scene. You should keep in mind the terms in bold — make sure you understand them.

In the said “book” you put transactions (info about what happened with your money, properties etc. etc.). These transactions are also called records — you record them somewhere in a secure way and so everyone can see them.

The transactions are organized into so-called blocks. Blocks are data structures where transactions are permanently recorded. One block can contain hundreds or thousands of transactions. Transactions can vary in size but on average are about 250Bytes, so each block can contain about 4000 transactions.

Cryptography is the tool for ensuring that the blockchain is created securely — no one can receive the same money twice, one property cannot belong to more people, everyone can see and verify what transactions have been recorded to the blocks.

Source: building 1, building 2, building 3 (you can thank me later for lego recommendations.)

In reality, the blocks look kind of ugly. Below you can see an example of a single block — the Block 170 — a special block. It contains the first ever bitcoin transaction between two humans.

Why does the block look this way? It is a result of a “cryptographic process”. This is, in part, what the code behind a rudimentary blockchain looks like.

Back to the question that quite a few people are asking:

“Is blockchain the same as bitcoin?”

Blockchain is the technology that underpins Bitcoin and it was developed specifically for Bitcoin. So, Bitcoin was the first example of blockchain in action. That’s why the two names are so often used interchangeably.

Debunking asymmetric cryptography

The cryptography used for recording blockcs to blockchain is one of more common types of cryptography. We have two basic types:
1. Symmetric

2. Asymmetric

I have seen a third type — hash functions — as a separate type. However, we will not dive into other ways of encryption here. Instead we break down the asymmetric (public key) cryptography, which is usually used for blockchain.

Imagine you own a house (which is not easy, considering the current market situation, but you can try to imagine.)

You probably also own a key to your house, maybe even a security code for front door alarm. Now, suppose you become friend with a colleague at work and you want to invite them for a coffee. Will you give them a copy of your key? Probably not. Your key is your property. It is your private key that you keep for yourself.

But you still want to invite that friend, so they need some info about your house. So you give them your address — an information that the friend uses to reach you. You can give this address more friends, they can share it and if you forget, you can just look at your mailbox where the address is writen, or just see a cadaster. This is like a public key.

In a proper terminology, private key is used to decrypt the data (unlock the house and your mailbox, where you have received your message). Public key is used to encrypt the data (to send your message to the recipient).

Recall that cryptography is a tool for writing transactions into blocks with the intention of keeping the data secret and safe. In the asymmetric cryptography, two keys are used: the public key for encryption and the private key for decryption.

Why is asymmetric cryptography cooler?

Now, back to the two types of cryptography. The one we just described is the asymmetric one. How does it differ from the symmetric one?

Symmetric — involves only one key to encrypt and decrypt data. Imagine that you want someone to send you a gift to your home address, so you give them a copy of your own key to go to your house and put the gift in your living room.

2. Asymmetric — uses public key (to encrypt the data) and private key (to decrypt the data).

So what are two big advantages of asymmetric cryptography?

It is computationally impossible to derive the private key corresponding to a given public key. There is some cool math behind why is this impossible, which we explain in the next part about elliptic curves.
It is possible to prove that you know the private key corresponding to a public key without revealing any useful information about the private key itself.

There are more types of asymmetric cryptography — two of them being very common. One is the elliptic curves cryptography, the other is RSA cryptography which somehow revolves around prime numbers.

Summary

Blockchain is something like a big “accounting book” of transactions (records).
Transactions are pieces of data (info about money transactions, ownership, art etc.) that someone records.
Block is a set of transactions.
Cryptography is a method to encrypt and decrypt a secret message. Among other things, it is used to create blockchain.
One of the main types of cryptography is the asymmetric cryptography — that is often used in blockchain technology.
Public key and private key are the key components (haha) of asymmetric cryptography. Public key is known publicly and used to encrypt a message that you want to send. Private key is known only to its owner and is used to decrypt the message.
Asymmetric cryptography has more types, such as elliptice curves cryptography, which will be explained in the second part of this series.

Did you like this article a bit and would like to read part two about elliptic curves? 〰️➿

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