# What is Blockchain?

<mark style="color:$info;">Blockchain can be described as a value-exchange protocol. It can be used to track ownership, transfers and provenance of assets.</mark>

<figure><img src="https://2773531205-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FwPYQpCxrPJoaRvqUIVza%2Fuploads%2FE5Q2fESqD08H8gHKTnIW%2FWhat%20is%20Blockchain.png?alt=media&#x26;token=a0f3536b-44c0-4ad1-9d9f-a5752c61542f" alt=""><figcaption></figcaption></figure>

## 🧠 Cypherpunks and Digital Currency

<mark style="color:$info;">In the 1990s,</mark> <mark style="color:$info;"></mark><mark style="color:$info;">**Cypherpunks**</mark> <mark style="color:$info;"></mark><mark style="color:$info;">began to experiment with the concept of a</mark> <mark style="color:$info;"></mark><mark style="color:$info;">**digital currency**</mark> <mark style="color:$info;"></mark><mark style="color:$info;">that was not dependent on an organization issuing it.</mark>

<mark style="color:$info;">This sort of digital money would be:</mark>

* <mark style="color:$info;">Identifiable as being</mark> <mark style="color:$info;"></mark><mark style="color:$info;">**scarce**</mark> <mark style="color:$info;"></mark><mark style="color:$info;">and</mark> <mark style="color:$info;"></mark><mark style="color:$info;">**limited in supply**</mark>
* <mark style="color:$info;">Acceptable as money since it would be</mark> <mark style="color:$info;"></mark><mark style="color:$info;">**provably difficult to create**</mark>

<mark style="color:$info;">In</mark> <mark style="color:$info;"></mark><mark style="color:$info;">**1998**</mark><mark style="color:$info;">,</mark> <mark style="color:$info;"></mark><mark style="color:$info;">**Wei Dai**</mark> <mark style="color:$info;"></mark><mark style="color:$info;">proposed</mark> <mark style="color:$info;"></mark><mark style="color:$info;">**“b-money”**</mark><mark style="color:$info;">, an anonymous, distributed electronic cash system.</mark>\
\&#xNAN;*<mark style="color:$info;">b-money was never implemented</mark>*<mark style="color:$info;">, but it inspired later work on blockchain.</mark>

<figure><img src="https://2773531205-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FwPYQpCxrPJoaRvqUIVza%2Fuploads%2F0taNQHYgt65b57e1Vn6I%2FWei%20Dai.png?alt=media&#x26;token=64922ebb-3f48-4085-8c1e-c5259ce83b81" alt=""><figcaption></figcaption></figure>

{% hint style="info" %}
*b-money was never implemented*, but it inspired later work on blockchain.
{% endhint %}

<mark style="color:$info;">In</mark> <mark style="color:$info;"></mark><mark style="color:$info;">**2004**</mark><mark style="color:$info;">, a system called</mark> <mark style="color:$info;"></mark><mark style="color:$info;">**Reusable Proof of Work**</mark> <mark style="color:$info;"></mark><mark style="color:$info;">was introduced by</mark> <mark style="color:$info;"></mark><mark style="color:$info;">**Hal Finney**</mark><mark style="color:$info;">.</mark>\ <mark style="color:$info;">This system was designed to</mark> <mark style="color:$info;"></mark><mark style="color:$info;">**enable users to verify the transfer of tokens in real-time**</mark><mark style="color:$info;">.</mark>

***

## 🚀 Then Came Bitcoin

<mark style="color:$info;">In</mark> <mark style="color:$info;"></mark><mark style="color:$info;">**2008**</mark><mark style="color:$info;">, an anonymous person or group using the pseudonym</mark> <mark style="color:$info;"></mark><mark style="color:$info;">**Satoshi Nakamoto**</mark> <mark style="color:$info;"></mark><mark style="color:$info;">introduced the concept of</mark> <mark style="color:$info;"></mark><mark style="color:$info;">**distributed blockchains**</mark><mark style="color:$info;">.</mark>

He modified the blockchain architecture to allow the addition of extra blocks without requiring them to be signed by trusted parties.

<figure><img src="https://2773531205-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FwPYQpCxrPJoaRvqUIVza%2Fuploads%2FH08WccVsDbUQvcjweTti%2FFirst%20Forum%20Post%20Introducing%20Bitcoin.png?alt=media&#x26;token=1f2e792f-a34b-40d0-a8c4-5cbc2df7ad7d" alt=""><figcaption></figcaption></figure>

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## ⛓️ What Is a Blockchain?

<figure><img src="https://2773531205-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FwPYQpCxrPJoaRvqUIVza%2Fuploads%2FEf8kYtNK0s0UHF1m1X4W%2FHow%20blockchain%20works.png?alt=media&#x26;token=41b3e372-f414-47c0-a5b9-c21ba3008535" alt=""><figcaption></figcaption></figure>

{% tabs %}
{% tab title="In a nutshell" %}
📘  A blockchain is a *distributed online database* made up of blocks (or ledgers), each containing a timestamp and a reference to the previous block.

It is:

* **Continuously growing**
* **Publicly verifiable**
* **Connected in sequence**
* **Tamper-resistant**

🛡️ Blockchain is often called a **distributed ledger** because it's:

* Verified by a **global network of computers**
* Not stored in any single location
* **More secure** from hacking

When a transaction occurs:

1. It is **broadcast to the network**
2. Each node **verifies and encrypts** it
3. Once verified, it is **added to the block**
4. The record is visible to all, but **user identities remain anonymous**
   {% endtab %}

{% tab title="Extensive " %}
Blockchain is often referred to as a distributed ledger because it is constantly being updated and verified by a network of computers around the world. It is not stored in a single location, which makes it more secure from hacking attacks. When a transaction is made, it is broadcast to the network, then each computer on the network verifies the transaction. Also each transaction is encrypted. Once the transaction is verified, it is added to the block. All this information is public and everyone can see the transactions that have been made. However, the identities of the people involved in the transaction are anonymous, as long as there is no link between your wallet address and your identity.
{% endtab %}
{% endtabs %}

***

## 📓 Simplifying Blockchain: The National Ledger

<figure><img src="https://2773531205-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FwPYQpCxrPJoaRvqUIVza%2Fuploads%2FBSk9ZtKKRtzcEs2p1L1Q%2FSimplifying%20Blockchain.png?alt=media&#x26;token=076c43df-d75c-44cd-962a-8af9da90e3eb" alt=""><figcaption></figcaption></figure>

{% tabs %}
{% tab title="In a nutshell" %}
Still confused? Think of a **blockchain as an accounting book**, or better yet, your country’s **national ledger**.

* Every event or transaction is recorded
* **No central authority** controls it
* Every citizen has a **copy**
* New updates are **shared with all**
  {% endtab %}

{% tab title="Extensive " %}
Still confused about what a blockchain actually is? Let’s simplify it. Think of a blockchain as an accounting book. You may ask, an accounting book of what? Think of it as a book or ledger for a specific network. Imagine it’s like your country’s national ledger or accounting book. In this ledger, every transaction or event that occurs within the country is meticulously recorded. Now, who’s in control of this ledger? Well, it’s not under the control of any single entity – it’s a collective effort. Every citizen in the country plays a role in maintaining this ledger, and every citizen gets an identical copy of it. Whenever a new transaction occurs, it’s added to the ledger, and this updated version is distributed to all citizens.
{% endtab %}
{% endtabs %}

***

## ⚠️ Stopping the Bad Guys

{% tabs %}
{% tab title="In a nutshell" %}
In any system, there will be bad actors who try to:

* Falsify transactions
* Inflate balances
* Create money from thin air

That would cause **inflation** and **harm the whole system**.

But in blockchain:

* The network **reviews all transactions**
* Ledgers are **compared across nodes**
* The **majority rules** and rejects fake entries

{% hint style="info" %}
This is **decentralization** in action: decisions made collectively by participants — **not by any central authority**.
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{% endtab %}

{% tab title="Extensive " %}
However, in any system, there’s always the potential for bad actors. These individuals might attempt to deceive the network by creating false transactions, claiming they have more money than they actually do. If these false transactions were accepted, it would essentially mean creating money out of thin air, leading to inflation and a devaluation of the currency. This harms everyone. That’s where the strength of decentralization comes into play.&#x20;

The citizens, or the network users, compare their ledger copies and review the transaction history to ensure the truth is being told. Through a democratic process, the majority determines whether to accept or reject these questionable transactions. This is the essence of decentralization in a blockchain. The power rests with the majority, and decisions are made collectively.&#x20;
{% endtab %}
{% endtabs %}

***

## 🧩 In a Nutshell

A **blockchain** is:

* A **decentralized**, **immutable**, online database
* Verified by a **global peer-to-peer network**
* Public but **pseudonymous**

{% hint style="info" %}
Just like each country has unique laws, **each blockchain** has its **own rules, structure, and goals**.
{% endhint %}