Blockchain use cases beyond crypto

Introduction

Blockchain is not just for money. It helps keep records safe and clear for many jobs.

Tracking where food comes from to keep it safe.

Making sure your medical records are private and correct.

Keeping track of who owns land or buildings.

Making voting fair and hard to cheat.

Sharing music or art rights so creators get paid.

Syntax

Blockchain / Solidity

blockchain {
  data: {
    key: value
  }
  hash: string
  previous_hash: string
  timestamp: datetime
}

This is a simple way to show how data is stored in a block.

Each block links to the one before it using previous_hash.

Examples

This block stores information about food origin for safety tracking.

Blockchain / Solidity

block {
  data: {"food_origin": "farm123"}
  hash: "abc123"
  previous_hash: "xyz789"
  timestamp: "2024-06-01T12:00:00Z"
}

This block keeps a medical record safe and private.

Blockchain / Solidity

block {
  data: {"medical_record": "patient456"}
  hash: "def456"
  previous_hash: "abc123"
  timestamp: "2024-06-01T12:05:00Z"
}

Sample Program

This program creates a simple blockchain to store different types of data beyond money, like food origin and medical records. It shows how each block links to the previous one with a hash.

Blockchain / Solidity

class Block:
    def __init__(self, data, previous_hash):
        from datetime import datetime
        import hashlib
        self.data = data
        self.timestamp = datetime.utcnow().isoformat()
        self.previous_hash = previous_hash
        self.hash = self.calculate_hash()

    def calculate_hash(self):
        sha = hashlib.sha256()
        sha.update((str(self.data) + self.timestamp + self.previous_hash).encode())
        return sha.hexdigest()


class Blockchain:
    def __init__(self):
        self.chain = [self.create_genesis_block()]

    def create_genesis_block(self):
        return Block("Genesis Block", "0")

    def add_block(self, data):
        previous_hash = self.chain[-1].hash
        new_block = Block(data, previous_hash)
        self.chain.append(new_block)

    def print_chain(self):
        for i, block in enumerate(self.chain):
            print(f"Block {i}:")
            print(f"  Data: {block.data}")
            print(f"  Timestamp: {block.timestamp}")
            print(f"  Hash: {block.hash}")
            print(f"  Previous Hash: {block.previous_hash}\n")


# Example: Tracking food origin and medical record
bc = Blockchain()
bc.add_block({"food_origin": "farm123"})
bc.add_block({"medical_record": "patient456"})
bc.print_chain()

Important Notes

Each block has a unique hash that depends on its data and the previous block's hash.

This linking makes it very hard to change old data without breaking the chain.

Blockchain can be used for many things that need safe, clear records.

Summary

Blockchain is useful beyond money for safe and clear records.

It links data blocks so changes are hard to hide.

Common uses include food safety, medical records, land ownership, voting, and creative rights.

Practice

1. Which of the following is a common use of blockchain technology beyond cryptocurrency?

easy

A. Creating new digital currencies only

B. Running traditional centralized databases

C. Tracking the origin and movement of goods in supply chains

D. Replacing all internet servers

Solution

1. Step 1: Understand blockchain beyond money

   Blockchain is used to keep safe and clear records, not just for digital money.

2. Step 2: Identify common non-crypto uses

   Tracking goods in supply chains is a popular use case to ensure transparency and trust.

3. Final Answer:

   Tracking the origin and movement of goods in supply chains -> Option C

4. Quick Check:

   Blockchain use beyond crypto = Tracking goods [OK]

Hint: Think of blockchain as a secure record keeper beyond money [OK]

Common Mistakes:

• Thinking blockchain only creates cryptocurrencies
• Confusing blockchain with regular databases
• Assuming blockchain replaces all internet servers

2. Which syntax correctly describes a smart contract in blockchain?

easy

A. contract SmartContract { function run() public {} }

B. smart contract run() {}

C. contract = SmartContract()

D. function smartContract run()

Solution

1. Step 1: Recognize smart contract syntax

   Smart contracts are written like small programs with a contract keyword and functions.

2. Step 2: Check syntax correctness

   contract SmartContract { function run() public {} } uses correct syntax with 'contract' keyword and function declaration.

3. Final Answer:

   contract SmartContract { function run() public {} } -> Option A

4. Quick Check:

   Correct smart contract syntax = contract SmartContract { function run() public {} } [OK]

Hint: Look for 'contract' keyword and function inside braces [OK]

Common Mistakes:

• Missing 'contract' keyword
• Using assignment instead of declaration
• Incorrect function declaration syntax

3. What will be the output of this simplified blockchain smart contract code snippet?

mapping(address => uint) public votes;
function vote() public {
  votes[msg.sender] += 1;
}
vote() called twice by same address.

medium

A. votes[msg.sender] = 1

B. votes[msg.sender] = 2

C. votes[msg.sender] = 0

D. Error: duplicate voting not allowed

Solution

1. Step 1: Understand the vote function

   Each call to vote() increases the caller's vote count by 1 in the votes mapping.

2. Step 2: Calculate votes after two calls

   Calling vote() twice adds 1 twice, so votes[msg.sender] becomes 2.

3. Final Answer:

   votes[msg.sender] = 2 -> Option B

4. Quick Check:

   Two votes increment count to 2 [OK]

Hint: Each call adds 1, so two calls add up to 2 [OK]

Common Mistakes:

• Assuming only one vote allowed
• Thinking votes reset after each call
• Confusing mapping with array

4. Identify the error in this blockchain voting smart contract snippet:

mapping(address => bool) public voted;
function vote() public {
  require(!voted[msg.sender]);
  voted[msg.sender] = true;
  votes += 1;
}

medium

A. votes variable is not declared

B. require statement syntax is wrong

C. voted mapping should be uint not bool

D. Function vote() missing return type

Solution

1. Step 1: Check variable declarations

   The code uses 'votes += 1' but 'votes' is not declared anywhere.

2. Step 2: Verify other parts

   require syntax and voted mapping type are correct; vote() functions in Solidity do not need return type.

3. Final Answer:

   votes variable is not declared -> Option A

4. Quick Check:

   Undeclared variable 'votes' causes error [OK]

Hint: Check if all variables used are declared [OK]

Common Mistakes:

• Assuming require syntax is wrong
• Thinking bool mapping is incorrect
• Expecting return type in void functions

5. You want to build a blockchain system to manage digital rights for music tracks. Which feature is most important to include beyond basic blockchain storage?

hard

A. Anonymous voting for favorite tracks

B. A cryptocurrency token for trading music

C. A centralized database for faster queries

D. Smart contracts to automate royalty payments

Solution

1. Step 1: Understand digital rights management needs

   Managing rights requires automatic, trustworthy payment distribution to artists.

2. Step 2: Identify blockchain feature for automation

   Smart contracts can run code to automate royalty payments when music is used or sold.

3. Step 3: Evaluate other options

   Cryptocurrency tokens and voting are unrelated; centralized database loses blockchain benefits.

4. Final Answer:

   Smart contracts to automate royalty payments -> Option D

5. Quick Check:

   Automate payments with smart contracts [OK]

Hint: Use smart contracts to automate rules and payments [OK]

Common Mistakes:

• Choosing cryptocurrency token instead of automation
• Using centralized database losing blockchain trust
• Confusing voting with rights management