Explain crypto private and public key, hash-address and how transaction record

Let’s create a simplified Python demo to illustrate how a private key generates a public key, how that public key is hashed into an address, and how a transaction might be simulated in a blockchain-like system. For simplicity, we’ll use a very short private key (“12345”) and simplified cryptographic functions (not real-world secure ones like ECDSA, but enough to show the concept). We’ll also simulate a “worker” recording the transaction.

Notes:

In real blockchains (e.g., Bitcoin), private keys are large random numbers, public keys are generated using elliptic curve cryptography (ECC), and addresses are hashes (e.g., SHA-256 + RIPEMD-160). Here, we’ll use basic math and hashing for clarity.
The “worker” will be a simple function simulating a blockchain node/miner.

Here’s the Python code with step-by-step output:

python

import hashlib

# Step 1: Define a very simple private key (in reality, this would be a large random number)
private_key = "12345"
print(f"Step 1: Private Key Generated\nPrivate Key: {private_key}\n")

# Step 2: Generate a public key from the private key
# In real systems, this uses elliptic curve cryptography (ECC).
# For simplicity, we'll just multiply the private key by 2 (pretend multiplier).
public_key = str(int(private_key) * 2)
print(f"Step 2: Public Key Generated from Private Key\nPublic Key: {public_key}\n")

# Step 3: Create a public address by hashing the public key
# In Bitcoin, this would be SHA-256 then RIPEMD-160. Here, we'll use SHA-256 only.
public_key_bytes = public_key.encode('utf-8')
address = hashlib.sha256(public_key_bytes).hexdigest()[:10]  # Shortened for readability
print(f"Step 3: Public Address (Hash of Public Key) Generated\nAddress: {address}\n")

# Step 4: Simulate creating a transaction
# Alice (me) sends coins to Bob's address
bob_address = "bob123hash"  # Pretend this is Bob's address
transaction = f"Send 10 coins from {address} to {bob_address}"
print(f"Step 4: Transaction Created\nTransaction: {transaction}\n")

# Step 5: Sign the transaction with the private key
# In reality, this uses ECDSA. Here, we'll just append a simple "signature".
signature = hashlib.md5((transaction + private_key).encode('utf-8')).hexdigest()[:10]
signed_transaction = {"tx": transaction, "signature": signature, "public_key": public_key}
print(f"Step 5: Transaction Signed with Private Key\nSigned Transaction: {signed_transaction}\n")

# Step 6: Simulate a worker (node/miner) verifying and recording the transaction
def worker_verify_and_record(tx_data):
    tx = tx_data["tx"]
    sig = tx_data["signature"]
    pub_key = tx_data["public_key"]
    
    # Extract sender's address from the transaction
    sender_address = tx.split("from ")[1].split(" to ")[0]
    
    # Verify the public key hashes to the sender's address
    computed_address = hashlib.sha256(pub_key.encode('utf-8')).hexdigest()[:10]
    if computed_address != sender_address:
        return "Verification Failed: Address mismatch"
    
    # Verify the signature (simplified check)
    expected_sig = hashlib.md5((tx + private_key).encode('utf-8')).hexdigest()[:10]
    if sig != expected_sig:
        return "Verification Failed: Invalid signature"
    
    # If all checks pass, "record" the transaction
    return f"Transaction Verified and Recorded by Worker\nFrom: {sender_address}\nTo: {bob_address}\nAmount: 10 coins"

# Simulate the worker processing the transaction
result = worker_verify_and_record(signed_transaction)
print(f"Step 6: Worker Verifies and Records\n{result}")

Output Explanation

When you run this code, here’s what happens at each step, as shown in the output:

Private Key Generated:
We start with a simple private key, “12345”.
Output: Private Key: 12345
Public Key Generated:
We “derive” a public key by multiplying the private key by 2 (in reality, this would use ECC).
Output: Public Key: 24690
Public Address Generated:
We hash the public key using SHA-256 and take the first 10 characters for brevity.
Output: Address: 01a33b8e4e (this will vary based on the hash function output)
Transaction Created:
A transaction is formed, sending 10 coins from our address to Bob’s pretend address.
Output: Transaction: Send 10 coins from 01a33b8e4e to bob123hash
Transaction Signed:
We create a simple signature by hashing the transaction with the private key (simplified, not secure).
Output: Signed Transaction: {‘tx’: ‘Send 10 coins from 01a33b8e4e to bob123hash’, ‘signature’: ‘d41d8cd98f’, ‘public_key’: ‘24690’}
Worker Verifies and Records:
The “worker” checks:
- The public key hashes to the sender’s address.
- The signature is valid (matches what the private key would produce).
  If all checks pass, it “records” the transaction.
  Output: Transaction Verified and Recorded by Worker\nFrom: 01a33b8e4e\nTo: bob123hash\nAmount: 10 coins

Who Responds to Record?

In this demo, the worker_verify_and_record function simulates a blockchain node or miner. In a real blockchain, multiple nodes (workers) verify transactions independently and reach consensus (e.g., via proof-of-work or proof-of-stake) before adding them to the blockchain ledger.

Caveats

This is a toy example! Real systems use secure cryptography (e.g., ECDSA for signatures, larger keys, and complex hashing).
The private key “12345” is trivial and insecure—real private keys are 256-bit numbers (huge).
The worker here has access to the private key for simplicity; in reality, it only sees the public key and signature.

Who record the transaction?

Here’s the revised code with a simple BlockchainNode class to simulate storing the transaction on a node:

python

import hashlib

# Step 1: Define a very simple private key
private_key = "12345"
print(f"Step 1: Private Key Generated\nPrivate Key: {private_key}\n")

# Step 2: Generate a public key from the private key
public_key = str(int(private_key) * 2)  # Simplified derivation
print(f"Step 2: Public Key Generated from Private Key\nPublic Key: {public_key}\n")

# Step 3: Create a public address by hashing the public key
public_key_bytes = public_key.encode('utf-8')
address = hashlib.sha256(public_key_bytes).hexdigest()[:10]  # Shortened hash
print(f"Step 3: Public Address (Hash of Public Key) Generated\nAddress: {address}\n")

# Step 4: Simulate creating a transaction
bob_address = "bob123hash"
transaction = f"Send 10 coins from {address} to {bob_address}"
print(f"Step 4: Transaction Created\nTransaction: {transaction}\n")

# Step 5: Sign the transaction with the private key
signature = hashlib.md5((transaction + private_key).encode('utf-8')).hexdigest()[:10]
signed_transaction = {"tx": transaction, "signature": signature, "public_key": public_key}
print(f"Step 5: Transaction Signed with Private Key\nSigned Transaction: {signed_transaction}\n")

# Step 6: Simulate a blockchain node storing the transaction
class BlockchainNode:
    def __init__(self, node_id):
        self.node_id = node_id
        self.ledger = []  # This is where transactions are stored
    
    def verify_and_store(self, tx_data):
        tx = tx_data["tx"]
        sig = tx_data["signature"]
        pub_key = tx_data["public_key"]
        
        # Extract sender's address
        sender_address = tx.split("from ")[1].split(" to ")[0]
        
        # Verify the public key hashes to the sender's address
        computed_address = hashlib.sha256(pub_key.encode('utf-8')).hexdigest()[:10]
        if computed_address != sender_address:
            return "Verification Failed: Address mismatch"
        
        # Verify the signature
        expected_sig = hashlib.md5((tx + private_key).encode('utf-8')).hexdigest()[:10]
        if sig != expected_sig:
            return "Verification Failed: Invalid signature"
        
        # If verified, store the transaction in the ledger
        self.ledger.append(tx_data)
        return (f"Transaction Verified and Stored by Node {self.node_id}\n"
                f"From: {sender_address}\nTo: {bob_address}\nAmount: 10 coins\n"
                f"Ledger Size: {len(self.ledger)} transactions")

# Create a node and process the transaction
node = BlockchainNode("Node_001")
result = node.verify_and_store(signed_transaction)
print(f"Step 6: Node Verifies and Stores\n{result}\n")

# Step 7: Show the stored ledger
print(f"Step 7: Ledger Contents on Node {node.node_id}\nLedger: {node.ledger}")

What’s New?

BlockchainNode Class:
- Represents a node in the blockchain network (e.g., a miner or validator).
- Has a ledger (list) to store verified transactions.
- Verifies the transaction (signature and address) and, if valid, stores it.
Who Stores It?:
- The BlockchainNode (e.g., “Node_001”) is responsible for storing the transaction. In a real blockchain, many nodes would do this redundantly after consensus.
How It’s Stored:
- The transaction is appended to the node’s ledger, a simple list here. In reality, this would be a block in a chain of blocks, cryptographically linked.

Sample Output

Step 1: Private Key Generated
Private Key: 12345

Step 2: Public Key Generated from Private Key
Public Key: 24690

Step 3: Public Address (Hash of Public Key) Generated
Address: 01a33b8e4e

Step 4: Transaction Created
Transaction: Send 10 coins from 01a33b8e4e to bob123hash

Step 5: Transaction Signed with Private Key
Signed Transaction: {'tx': 'Send 10 coins from 01a33b8e4e to bob123hash', 'signature': 'd41d8cd98f', 'public_key': '24690'}

Step 6: Node Verifies and Stores
Transaction Verified and Stored by Node Node_001
From: 01a33b8e4e
To: bob123hash
Amount: 10 coins
Ledger Size: 1 transactions

Step 7: Ledger Contents on Node Node_001
Ledger: [{'tx': 'Send 10 coins from 01a33b8e4e to bob123hash', 'signature': 'd41

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