Welcome to a series of posts where I document my thoughts and experiments as an avid tinkerer, learner, and explorer in Technology

Experiments : Creating my own Kenny Token Cryptocurrency

In the flurry of ICOs and the hype of cryprocurrencies, I set out to find out how simple it would be to create my own cryptocurrency.

As it turns out, it’s not difficult at all to create an ERC20 based token on the Ethereum network!

TL;DR - I managed to create KennyToken in under an hour!

kennytoken screenshot

Out of thin air, I created 100,000,000 KENNY tokens! You can find the creation of this on the Ethereum Ropsten Testnet Blockchain at https://ropsten.etherscan.io/token/0x9a170ac4b1458fe121498bf10693193b89d11d57

The source for Kenny Token is also available at

pragma solidity ^0.4.24;
// ----------------------------------------------------------------------------
// 'Kenny' token contract
//
// Deployed to : 0xB4097cba931F9f9d0eb18038F1E2C8cB3581c589
// Symbol : KENNY
// Name : Kenny Token
// Total supply: 100000000
// Decimals : 18
//
// Enjoy.
//
// (c) by Moritz Neto with BokkyPooBah / Bok Consulting Pty Ltd Au 2017. The MIT Licence.
// ----------------------------------------------------------------------------
// ----------------------------------------------------------------------------
// Safe maths
// ----------------------------------------------------------------------------
contract SafeMath {
function safeAdd(uint a, uint b) public pure returns (uint c) {
c = a + b;
require(c >= a);
}
function safeSub(uint a, uint b) public pure returns (uint c) {
require(b <= a);
c = a - b;
}
function safeMul(uint a, uint b) public pure returns (uint c) {
c = a * b;
require(a == 0 || c / a == b);
}
function safeDiv(uint a, uint b) public pure returns (uint c) {
require(b > 0);
c = a / b;
}
}
// ----------------------------------------------------------------------------
// ERC Token Standard #20 Interface
// https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md
// ----------------------------------------------------------------------------
contract ERC20Interface {
function totalSupply() public constant returns (uint);
function balanceOf(address tokenOwner) public constant returns (uint balance);
function allowance(address tokenOwner, address spender) public constant returns (uint remaining);
function transfer(address to, uint tokens) public returns (bool success);
function approve(address spender, uint tokens) public returns (bool success);
function transferFrom(address from, address to, uint tokens) public returns (bool success);
event Transfer(address indexed from, address indexed to, uint tokens);
event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
}
// ----------------------------------------------------------------------------
// Contract function to receive approval and execute function in one call
//
// Borrowed from MiniMeToken
// ----------------------------------------------------------------------------
contract ApproveAndCallFallBack {
function receiveApproval(address from, uint256 tokens, address token, bytes data) public;
}
// ----------------------------------------------------------------------------
// Owned contract
// ----------------------------------------------------------------------------
contract Owned {
address public owner;
address public newOwner;
event OwnershipTransferred(address indexed _from, address indexed _to);
constructor() public {
owner = msg.sender;
}
modifier onlyOwner {
require(msg.sender == owner);
_;
}
function transferOwnership(address _newOwner) public onlyOwner {
newOwner = _newOwner;
}
function acceptOwnership() public {
require(msg.sender == newOwner);
emit OwnershipTransferred(owner, newOwner);
owner = newOwner;
newOwner = address(0);
}
}
// ----------------------------------------------------------------------------
// ERC20 Token, with the addition of symbol, name and decimals and assisted
// token transfers
// ----------------------------------------------------------------------------
contract KennyToken is ERC20Interface, Owned, SafeMath {
string public symbol;
string public name;
uint8 public decimals;
uint public _totalSupply;
mapping(address => uint) balances;
mapping(address => mapping(address => uint)) allowed;
// ------------------------------------------------------------------------
// Constructor
// ------------------------------------------------------------------------
constructor() public {
symbol = "KENNY";
name = "Kenny Token";
decimals = 18;
_totalSupply = 100000000000000000000000000;
balances[0xB4097cba931F9f9d0eb18038F1E2C8cB3581c589] = _totalSupply;
emit Transfer(address(0), 0xB4097cba931F9f9d0eb18038F1E2C8cB3581c589, _totalSupply);
}
// ------------------------------------------------------------------------
// Total supply
// ------------------------------------------------------------------------
function totalSupply() public constant returns (uint) {
return _totalSupply - balances[address(0)];
}
// ------------------------------------------------------------------------
// Get the token balance for account tokenOwner
// ------------------------------------------------------------------------
function balanceOf(address tokenOwner) public constant returns (uint balance) {
return balances[tokenOwner];
}
// ------------------------------------------------------------------------
// Transfer the balance from token owner's account to to account
// - Owner's account must have sufficient balance to transfer
// - 0 value transfers are allowed
// ------------------------------------------------------------------------
function transfer(address to, uint tokens) public returns (bool success) {
balances[msg.sender] = safeSub(balances[msg.sender], tokens);
balances[to] = safeAdd(balances[to], tokens);
emit Transfer(msg.sender, to, tokens);
return true;
}
// ------------------------------------------------------------------------
// Token owner can approve for spender to transferFrom(...) tokens
// from the token owner's account
//
// https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md
// recommends that there are no checks for the approval double-spend attack
// as this should be implemented in user interfaces
// ------------------------------------------------------------------------
function approve(address spender, uint tokens) public returns (bool success) {
allowed[msg.sender][spender] = tokens;
emit Approval(msg.sender, spender, tokens);
return true;
}
// ------------------------------------------------------------------------
// Transfer tokens from the from account to the to account
//
// The calling account must already have sufficient tokens approve(...)-d
// for spending from the from account and
// - From account must have sufficient balance to transfer
// - Spender must have sufficient allowance to transfer
// - 0 value transfers are allowed
// ------------------------------------------------------------------------
function transferFrom(address from, address to, uint tokens) public returns (bool success) {
balances[from] = safeSub(balances[from], tokens);
allowed[from][msg.sender] = safeSub(allowed[from][msg.sender], tokens);
balances[to] = safeAdd(balances[to], tokens);
emit Transfer(from, to, tokens);
return true;
}
// ------------------------------------------------------------------------
// Returns the amount of tokens approved by the owner that can be
// transferred to the spender's account
// ------------------------------------------------------------------------
function allowance(address tokenOwner, address spender) public constant returns (uint remaining) {
return allowed[tokenOwner][spender];
}
// ------------------------------------------------------------------------
// Token owner can approve for spender to transferFrom(...) tokens
// from the token owner's account. The spender contract function
// receiveApproval(...) is then executed
// ------------------------------------------------------------------------
function approveAndCall(address spender, uint tokens, bytes data) public returns (bool success) {
allowed[msg.sender][spender] = tokens;
emit Approval(msg.sender, spender, tokens);
ApproveAndCallFallBack(spender).receiveApproval(msg.sender, tokens, this, data);
return true;
}
// ------------------------------------------------------------------------
// Don't accept ETH
// ------------------------------------------------------------------------
function () public payable {
revert();
}
// ------------------------------------------------------------------------
// Owner can transfer out any accidentally sent ERC20 tokens
// ------------------------------------------------------------------------
function transferAnyERC20Token(address tokenAddress, uint tokens) public onlyOwner returns (bool success) {
return ERC20Interface(tokenAddress).transfer(owner, tokens);
}
}
view raw kennytoken.sol hosted with ❤ by GitHub

Prior knowledge before exploration

Solidity programming language

Much of the heavy lifting in creating an ERC20 cryptocurrency has been done and is available as public references, eg

Learning Solidity was made easy and fun with CryptoZombies - a game where you progress thru the levels by learning and completing Solidity code

Next explorations

Having explored a bit of Solidity as a programming language, the next steps are to explore creating smart contracts with a framework.

Frameworks that ease development by including built-in support for automated testing for smart contracts, support for deployment management to testnet and mainnet, and frameworks that cover both the backend smart contract as well as the frontend via Web3.js

A shortlist includes