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new file: Blockchain/Blockchain.sm
new file: Blockchain/SigningKey.sm new file: Blockchain/main.sf
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‎Blockchain/Blockchain.sm

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#!/usr/bin/ruby
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# Code translated from:
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# https://github.com/Savjee/SavjeeCoin
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include SigningKey
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import SigningKey::SigningKey
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class Transaction(fromAddress, String toAddress, Number amount) {
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has timestamp = Date()
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has signature = nil
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# Creates a SHA256 hash of the transaction
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-> calculateHash() -> String {
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[fromAddress, toAddress, amount, timestamp].dump.sha256
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}
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/*
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* Signs a transaction with the given signingKey (which is an Elliptic keypair
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* object that contains a private key). The signature is then stored inside the
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* transaction object and later stored on the blockchain.
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*/
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-> signTransaction(SigningKey signingKey) {
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# You can only send a transaction from the wallet that is linked to your
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# key. So here we check if the fromAddress matches your publicKey
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if (signingKey.getPublic != fromAddress) {
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die('You cannot sign transactions for other wallets!')
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}
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# Calculate the hash of this transaction, sign it with the key
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# and store it inside the transaction obect
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const hashTx = self.calculateHash
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const sig = signingKey.sign(hashTx)
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signature = sig
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}
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/**
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* Checks if the signature is valid (transaction has not been tampered with).
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* It uses the fromAddress as the public key.
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*/
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-> isValid() -> Bool {
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# If the transaction doesn't have a from address we assume it's a
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# mining reward and that it's valid. You could verify this in a
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# different way (special field for instance)
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if (fromAddress == nil) {
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return true
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}
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if (signature == nil) {
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die ('No signature in this transaction');
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}
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SigningKey().keyFromPublic(fromAddress).verify(signature, self.calculateHash)
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}
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}
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class Blockchain::Block (Date timestamp, Array transactions, String previousHash = '') {
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has nonce = 0
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has hash = nil
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method init {
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hash = self.calculateHash
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}
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/**
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* Returns the SHA256 of this block (by processing all the data stored
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* inside this block)
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*/
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-> calculateHash() -> String {
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[previousHash, timestamp, transactions, nonce].dump.sha256
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}
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/**
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* Starts the mining process on the block. It changes the 'nonce' until the hash
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* of the block starts with enough zeros (= difficulty)
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*/
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-> mineBlock(Number difficulty) {
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var target_prefix = "0"*difficulty
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while (hash.first(difficulty) != target_prefix) {
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++nonce
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hash = self.calculateHash
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}
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STDERR.say("Block mined: #{hash}")
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}
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/**
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* Validates all the transactions inside this block (signature + hash) and
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* returns true if everything checks out. False if the block is invalid.
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*/
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-> hasValidTransactions() -> Bool {
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transactions.all { .isValid }
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}
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}
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class Blockchain (Number difficulty = 2, Array pendingTransactions = [], Number miningReward = 100) {
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has chain = []
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method init {
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chain = [self.createGenesisBlock]
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}
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-> createGenesisBlock() -> Blockchain::Block {
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Blockchain::Block(Date.parse('2021-10-07', '%Y-%m-%d'), [], '0')
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}
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/**
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* Returns the latest block on our chain. Useful when you want to create a
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* new Block and you need the hash of the previous Block.
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*/
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-> getLatestBlock() -> Blockchain::Block {
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chain.last
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}
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/**
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* Takes all the pending transactions, puts them in a Block and starts the
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* mining process. It also adds a transaction to send the mining reward to
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* the given address.
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*/
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-> minePendingTransactions(String miningRewardAddress) {
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const rewardTx = Transaction(nil, miningRewardAddress, miningReward)
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pendingTransactions.push(rewardTx)
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const block = Blockchain::Block(Date.now, pendingTransactions, self.getLatestBlock.hash)
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block.mineBlock(difficulty)
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STDERR.say('Block successfully mined!')
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chain.push(block)
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pendingTransactions = []
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}
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/**
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* Add a new transaction to the list of pending transactions (to be added
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* next time the mining process starts). This verifies that the given
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* transaction is properly signed.
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*/
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-> addTransaction(Transaction transaction) {
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if (!transaction.fromAddress || !transaction.toAddress) {
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die('Transaction must include from and to address')
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}
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# Verify the transaction
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if (!transaction.isValid()) {
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die('Cannot add invalid transaction to chain')
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}
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if (transaction.amount <= 0) {
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die('Transaction amount should be higher than 0')
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}
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# Making sure that the amount sent is not greater than existing balance
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if (self.getBalanceOfAddress(transaction.fromAddress) < transaction.amount) {
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die('Not enough balance')
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}
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pendingTransactions.push(transaction)
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self
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}
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/**
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* Returns the balance of a given wallet address.
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*/
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-> getBalanceOfAddress(String address) -> Number {
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var balance = 0;
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chain.each {|block|
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block.transactions.each {|trans|
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if (trans.fromAddress == address) {
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balance -= trans.amount
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}
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if (trans.toAddress == address) {
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balance += trans.amount
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}
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}
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}
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return balance
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}
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/**
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* Returns a list of all transactions that happened
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* to and from the given wallet address.
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*/
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-> getAllTransactionsForWallet(String address) -> Array {
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var txs = []
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chain.each {|block|
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block.transactions.each {|tx|
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if ((tx.fromAddress == address) || (tx.toAddress == address)) {
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txs.push(tx)
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}
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}
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}
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STDERR.printf("get transactions for wallet count: %s\n", txs.length)
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return txs
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}
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/**
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* Loops over all the blocks in the chain and verify if they are properly
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* linked together and nobody has tampered with the hashes. By checking
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* the blocks it also verifies the (signed) transactions inside of them.
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*/
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-> isChainValid() -> Bool {
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# Check if the Genesis block hasn't been tampered with by comparing
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# the output of createGenesisBlock with the first block on our chain
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if (self.createGenesisBlock.dump != chain.first.dump) {
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return false
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}
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# Check the remaining blocks on the chain to see if there hashes and
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# signatures are correct
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chain.each_cons(2, {|previousBlock, currentBlock|
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if (previousBlock.hash != currentBlock.previousHash) {
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return false
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}
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if (!currentBlock.hasValidTransactions) {
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return false
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}
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if (currentBlock.hash != currentBlock.calculateHash) {
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return false
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}
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})
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return true
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}
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}

‎Blockchain/SigningKey.sm

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#!/usr/bin/ruby
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var Ed25519 = require('Crypt::PK::Ed25519')
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class SigningKey() {
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has key = Ed25519.new.generate_key
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method keyFromPublic(String public) {
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key = Ed25519.new
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key.import_key_raw(pack('H*', public), 'public')
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self
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}
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method keyFromPrivate(String private) {
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key = Ed25519.new
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key.import_key_raw(pack('H*', private), 'private')
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self
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}
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method load(String file) {
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var private = File(file).read
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self.keyFromPrivate(private)
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}
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method store(String file) {
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File(file).write(self.getPrivate)
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self
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}
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method getPublic() {
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unpack('H*', key.export_key_raw('public'))
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}
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method getPrivate() {
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unpack('H*', key.export_key_raw('private'))
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}
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method sign(String message) {
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unpack('H*', key.sign_message(message))
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}
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method verify(String sig, String message) {
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key.verify_message(pack('H*', sig), message) ? true : false
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}
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}

‎Blockchain/main.sf

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#!/usr/bin/ruby
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include Blockchain
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include SigningKey
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import Blockchain::Blockchain
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import Blockchain::Transaction
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import SigningKey::SigningKey
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# Your private key goes here
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var myKey = SigningKey()
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# Another key
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var evilKey = SigningKey()
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STDERR.printf("Your private key: %s\n", myKey.getPrivate)
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# From that we can calculate your public key (which doubles as your wallet address)
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var myWalletAddress = myKey.getPublic
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# Create new instance of Blockchain class
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var sidefCoin = Blockchain(difficulty: 2)
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# Mine first block
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sidefCoin.minePendingTransactions(myWalletAddress)
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# Create a transaction & sign it with your key
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const tx1 = Transaction(myWalletAddress, evilKey.getPublic, 100)
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tx1.signTransaction(myKey)
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#tx1.signTransaction(evilKey)
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sidefCoin.addTransaction(tx1)
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# Mine block
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sidefCoin.minePendingTransactions(myWalletAddress)
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# Create second transaction
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const tx2 = Transaction(myWalletAddress, evilKey.getPublic, 50)
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tx2.signTransaction(myKey)
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sidefCoin.addTransaction(tx2)
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# Mine block
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sidefCoin.minePendingTransactions(evilKey.getPublic)
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# Create third transaction
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const tx3 = Transaction(evilKey.getPublic, myWalletAddress, 10)
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tx3.signTransaction(evilKey)
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sidefCoin.addTransaction(tx3)
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# Mine block
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sidefCoin.minePendingTransactions(myWalletAddress)
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STDERR.say("\nMy balance is: #{sidefCoin.getBalanceOfAddress(myWalletAddress)}")
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STDERR.say("Evil balance is: #{sidefCoin.getBalanceOfAddress(evilKey.getPublic)}")
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# Uncomment this line if you want to test tampering with the chain
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#sidefCoin.chain[1].transactions[0].amount = 10;
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# Check if the chain is valid
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STDERR.say("\nBlockchain valid? ", sidefCoin.isChainValid() ? 'Yes' : 'No')

‎README.md

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### Summary
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* Blockchain
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* [Blockchain](./Blockchain/Blockchain.sm)
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* [Main](./Blockchain/main.sf)
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* [SigningKey](./Blockchain/SigningKey.sm)
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* Converters
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* [Any2audio](./Converters/any2audio.sf)
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* [Any2mp3](./Converters/any2mp3.sf)

‎update_readme.pl

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my $title = $file->{name} =~ tr/_/ /r =~ s/ s /'s /gr;
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if ($file->{name} =~ /\.(\w{2,3})\z/) {
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next if $1 !~ /^sf\z/i;
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next if $1 !~ /^(?:sf|sm)\z/i;
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}
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if (-d $file->{path}) {
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}
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else {
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next if $dir eq $main_dir;
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my $naked_title = $title =~ s/\.sf\z//ri;
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my $naked_title = $title =~ s/\.(?:sf|sm)\z//ri;
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my $url_path = uri_escape($make_section_url->($file->{name}), ' ');
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$section .= (' ' x $spaces) . "* [\u$naked_title]($url_path)\n";
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}

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