Blockchain A-Z: Build a Blockchain, Crypto, & Smart Contract

Master blockchain fundamentals through a plan of attack that covers high-level overviews, cryptography, SHA-256, immutable ledger, mining, Byzantine fault tolerance, and consensus with hands-on tutorials and visual demos.

Explore how a blockchain forms a cryptographically linked chain of blocks, each with its own hash and the previous hash, creating an immutable ledger and protecting against tampering.

Explore how SHA256 hash creates a 64-character hexadecimal fingerprint (256-bit) of any digital document and underpins blockchain by illustrating determinism, the avalanche effect, and one-way collision resistance.

Explore how the immutable ledger of blockchains links blocks with cryptographic hashes, preventing tampering and protecting ownership records like title deeds in government ledgers.

Expand the blockchain across thousands of computers in a distributed peer-to-peer network, use majority consensus to detect tampering, and restore data when errors occur, enabling trust in a trustless environment.

Explore how mining secures blockchains by varying the nonce to influence the hash, linking blocks with the previous hash while handling multiple transactions and preserving an immutable ledger.

Miners iterate nonces to generate hashes below a target, using SHA-256, leading zeros, and the avalanche effect to secure a block and advance the blockchain.

Explore the Byzantine fault tolerance concept through the generals problem, using majority-based consensus to withstand traitors, and see how blockchain and decentralized systems tolerate up to one third traitors.

Explore how consensus protocols defend the blockchain from attackers and resolve competing chains, with a focus on proof-of-work mining, nonce puzzles, block verification, and incentives.

Explore how proof-of-work resolves block conflicts by extending the longest chain through hashing power and consensus. See how majority hashing power determines consensus and how orphan blocks and rewards emerge.

Demonstrate how blockchains secure data with sha-256 hashing, mining, and linked blocks. Observe tamper resistance across a distributed peer-to-peer network and token transactions.

Set up your Python environment with Anaconda and Spyder, build a general blockchain, then decentralize it into the at coin cryptocurrency and create a smart contract for a simulated ICO.

Install Flask and Postman to build and test a blockchain: set up a web app with Flask and use Postman to mine blocks and manage AT coin transactions.

Start building a blockchain architecture using a class, initialize the chain, and create the genesis block, then define a create block method to mine future blocks.

Define a create_block function that builds the next block after mining, using the mined proof and previous_hash to set block's index, timestamp, proof, and previous_hash, then append and return it.

Define a get_previous_block method that returns the last block from the blockchain using self.chain[-1], setting up the upcoming proof of work and mining step.

Explore how a proof of work uses a hard to find, easy to verify puzzle with previous and new proofs, a non-symmetric sha256 hash, and four leading zeros.

Develop a blockchain validation function that checks each block's proof of work (four leading zeros) and the previous hash using a sha256 hash of sorted json blocks.

Learn to implement is_chain_valid in this blockchain tutorial, validating each block by comparing previous hashes and verifying proof of work with four leading zeros, completing part one.

Build a Flask-based web app to interact with your blockchain, mine a block through proof of work, and retrieve the full chain via simple get requests.

Implement a Flask route mine_block to mine a new block by solving proof_of_work with the previous block, then return the mined block via JSON with HTTP 200.

Create a get chain endpoint to fetch and display the full blockchain as JSON, including the chain data and its length, via a get request in Postman.

Run a Flask-based blockchain demo, test GET chain, mine blocks, and POST requests via Postman, and verify the Genesis block with proof one and previous hash zero. Explore decentralized networks.

Demonstrate the homework solution by using the is chain valid function to check blockchain validity via the is valid get request and test it with Postman.

Plan module two strategy, covering Bitcoin basics, the technology, protocol, and token layers, and the software-governed monetary policy. Explore mining, mempools, orphaned blocks, 51% attack, and mining hardware.

Explore how Bitcoin is a protocol, not just a coin, enabling blockchain-based transactions across three layers: technology, protocol and coin, and token.

Bitcoin's monetary policy is controlled by its software, featuring a halving every 210,000 blocks, four years, reducing the reward from 50 to 25 to 12.5, with a 21 million cap.

Understand mining difficulty by comparing the current target to the max target and the effect of leading zeros. See how two-week adjustments stabilize Bitcoin mining.

Tour a Bitcoin mine to see how mining operates at scale. Learn how hash power, cooling, and energy use fuel rigs to solve cryptographic puzzles and enforce proof of work.

Discover how mining pools combine hashing power to distribute the nonce search across members, avoid double work, and reward contributions proportionally while relieving solo miners' headaches.

Explore the nonce range in blockchain mining, a 32-bit 4 billion value, how varying the nonce changes the hash to meet the target, and how the timestamp creates new opportunities.

Learn how miners select unconfirmed transactions from the mempool by prioritizing higher fees, while mining pools allocate work and adjust blocks via nonce and timestamp.

Miners fill blocks near one megabyte, prioritizing high-fee transactions as demand shifts; charts show transactions per block and fee trends, with mining pools offering transaction accelerators.

Explore how mining hardware evolved from CPUs to GPUs to ASICs, compare SHA-256 and ETH hash, and discuss cloud mining and memory-hard constraints.

Discover how mempools act as distributed staging areas for transactions in a peer-to-peer blockchain network, with each node maintaining its own mempool and relaying transactions until mined into a block.

Explore how orphaned blocks occur when two chains exist, learn why the longest chain wins, and why six confirmations protect against double spending and mempool activity.

Discover what the 51% attack is and is not, showing how majority hash power can rewrite the chain, cause a double spend, and disrupt mempool confirmations until longest chain wins.

Derive the current target from the block's bits field by decoding hexadecimal, determining the byte length, and constructing the 64-digit hex target used in blockchain difficulty.

Explore how blockchain transactions work, focusing on UTXO models, wallets, signatures with private and public keys, and privacy, then demystify fees, SegWit, and HD wallets across Bitcoin and altcoins.

Explore how unspent transaction outputs drive Bitcoin transactions by linking inputs to outputs. Learn why each transaction spends full inputs and how change returns to the sender.

Explore where transaction fees come from by analyzing the difference between inputs and outputs in a bitcoin transaction, including change, multiple utxos, and the role of miners and blocks.

Explore how wallets compute your balance by scanning the blockchain for unspent transaction outputs (UTXOs). The wallet adds these outputs to show a balance, with no centralized ledger.

Explore how private and public keys enable secure, private transactions on a blockchain by signing messages with a private key and verifying them with a public key.

Demonstrate how private keys generate public keys and how signatures verify transactions by linking a message to a private key via a public key for tamper-proof verification.

SegWit moves the signature data out of the main transaction into its own channel as a backward-compatible soft fork, freeing space to include more transactions within a one-megabyte block.

Differentiate public key and bitcoin address, noting the address is derived from the public key via SHA-256. Keep the private key secret and use the address to receive funds.

Explore hierarchically deterministic wallets and how a master private key derives multiple private keys, public keys, and addresses using bip32 to enhance privacy while enabling oversight.

Create the Hadcoin cryptocurrency by extending the module 1 blockchain, decentralize the network across multiple nodes, mine blocks, and implement consensus using Python, Flask, and the requests library.

Build a cryptocurrency by adding transactions and a basic consensus across nodes. Create a pre-block transactions list, implement add_transaction, and manage block indexing before mining.

Implement transaction handling and block creation to turn a blockchain into cryptocurrency. Prepare a consensus mechanism that synchronizes the longest chain across a decentralized network of nodes.

Implement the replace_chain method to solve the consensus problem by replacing the current chain with the longest chain from the network of nodes, using get_chain responses and is_chain_valid checks. The method iterates over network nodes, compares chain lengths, validates candidates, updates self.chain when a longer valid chain exists, and returns true or false to indicate replacement.

Mine the blockchain to convert it into a cryptocurrency by integrating transactions, creating a random node address, and posting new transactions to blocks.

Enable a post request to add a transaction to the blockchain by posting a JSON with sender, receiver, and amount; return the next block index and a 201 status.

Learn how to decentralize a blockchain by connecting new nodes with a post request and JSON file, then replace out-of-date chains to achieve consensus across the network.

Implement the replace_chain endpoint to replace the chain with the longest one, using is_chain_replaced, a get request, and a json node list for network synchronization.

Prepare JSON files for node addresses and transactions, set up three Python servers on ports 5001–5003, and format a ready-to-post had coins transaction for Postman.

Demonstrate building a decentralized blockchain by running three nodes, connecting them with Postman, mining blocks, and transferring AdCoin to demonstrate consensus via chain replacement.

Explore Ethereum fundamentals, smart contracts, and decentralized applications. Understand the Ethereum Virtual Machine, gas, DAOs, forks, initial coin offerings, white papers, and Web 3.0 implications.

Explore ethereum, a platform for building on top of its blockchain through smart contracts. See how it enables a decentralized world computer that runs programs across participant computers.

Explain that smart contracts are code running on the blockchain, executing if this then that and updating state across all nodes. Contrast Bitcoin Script and Solidity's Turing completeness and loops.

Decentralized applications use a front end and smart contracts as the API to interact with the blockchain, as shown by Steemit's twitter-like, blockchain-based interface.

Explain how the Ethereum Virtual Machine isolates smart contracts to protect privacy and prevent viruses. Describe how the gas system prices each operation, stopping infinite loops and encouraging efficient code.

Explore decentralized autonomous organizations and how smart contracts on the blockchain automate governance, operations, and growth without traditional human management.

Study the 2016 DAO attack on Ethereum, where a smart contract flaw led to a $50 million hack and a hard fork that split Ethereum and Ethereum Classic.

Learn the difference between soft and hard forks in blockchain, including Ethereum and Ethereum Classic after the DAO attack, and Bitcoin's SegWit, Bitcoin Cash, and Bitcoin Gold forks.

Explore soft and hard forks with real-life Bitcoin and Ethereum examples, compare tightening versus loosening rules, and understand how block size debates and SegWit shape the blockchain.

Explore how ICOs fund ideas on token and protocol layers and compare them to IPOs. See how tokens differ from shares, giving funding without ownership in traditional companies.

Analyze an ico case study where a founder issues 1 million tokens, sells half at $2, and crowds funds a theme park, illustrating token use and speculative demand.

Explore how blockchain startups use whitepapers to explain tokens, coins, and decentralized storage or energy platforms, and learn to identify strong projects like Sia, Power Ledger, and Provenance.

Compare web 2.0's centralized servers and interactive frontends with web 3.0's decentralized blockchain and smart contracts, and explore user data ownership and devices powering networks.