🪙 Crypto - A Simple Java Blockchain Implementation

This is a basic blockchain implementation in Java, demonstrating core blockchain concepts like blocks, mining, transactions, digital signatures, and wallets.

---

📁 Project Structure

Crypto/
├── src/
│   └── main/
│       └── java/
│           └── org/
│               └── arun/
│                   ├── Block.java
│                   ├── NoobChain.java
│                   ├── StringUtil.java
│                   ├── Transaction.java
│                   ├── TransactionInput.java
│                   ├── TransactionOutput.java
│                   └── Wallet.java
├── pom.xml
└── README.md

---

🚀 Getting Started

Prerequisites

• Java 8 or higher
• Maven
• IDE (e.g., IntelliJ IDEA)

Dependencies

Make sure your pom.xml includes the following (already set if you're running correctly):

<dependencies>
    <dependency>
        <groupId>org.bouncycastle</groupId>
        <artifactId>bcprov-jdk15on</artifactId>
        <version>1.70</version>
    </dependency>
    <dependency>
        <groupId>com.google.code.gson</groupId>
        <artifactId>gson</artifactId>
        <version>2.13.1</version>
    </dependency>
</dependencies>

---

🧠 How It Works

✅ Key Features

• Hashing with SHA-256
• Proof-of-Work mining with adjustable difficulty
• Transactions and Merkle root calculation
• ECDSA-based digital signatures for verification
• Basic wallet system with UTXO model
• Chain validation

---

▶️ Running the Project

Run the NoobChain.java main class from your IDE or via terminal:

mvn compile
mvn exec:java -Dexec.mainClass="org.arun.NoobChain"

---

💡 Sample Output

Creating and Mining Genesis block...
Transaction Successfully added to Block
Block Mined!!! : 000dda84948cae9926cfe5981e389403441ba26dad12dc04be214bf36c05bb73

WalletA's balance is: 100.0

WalletA is Attempting to send funds (40) to WalletB...
Transaction Successfully added to Block
Block Mined!!! : 0003ac3480367f5ffb1fab75ebd18f58ec8c92e598c96be8cbf8d75d80ed9535

WalletA's balance is: 60.0
WalletB's balance is: 40.0

WalletA Attempting to send more funds (1000) than it has...
#Not Enough funds to send transaction. Transaction Discarded.
Block Mined!!! : 00053b3d124413dfaa74f99ad180ba8e1030a7f2bdcdb7661eece79f246f6e17

WalletA's balance is: 60.0
WalletB's balance is: 40.0

WalletB is Attempting to send funds (20) to WalletA...
Transaction Successfully added to Block

WalletA's balance is: 80.0
WalletB's balance is: 20.0
Blockchain is valid

---

🛠️ To-Do / Improvements

• Implement network communication (P2P)
• Persistent storage (e.g., via database or file)
• Improved transaction pool and mempool logic
• Blockchain explorer (web UI)

---

📄 License

This project is licensed under the MIT License.

---

👤 Author

Arun –