DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

THE WORLD COMPUTER

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

"IBM System 360 tape drives" by Erik Pitti from San Diego, CA, USA - IBM System/360 MainframeUploaded by Mewtu. Licensed under CC BY 2.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:IBM_System_360_tape_drives.jpg#/media/File:IBM_System_360_tape_drives.jpg

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

The computer that anyone can program and everyone can trust

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

A planetary-scalevirtual machine:

Trusted Computation and Storage Service Platform

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Peer-to-peer network:

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Peer-to-peer network:Robust to connection problems and attacks

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Peer-to-peer network:New connections can be made to repair connectivity

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Intrinsic features include:

Cryptographic Identity Checking and Custom Payment Logic

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Three classes of instruction:1. Create a new Contract (program)2. Execute a Function of a specific Contract3. Transfer ether

Cryptographically Signed Instructions

State Data

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Ethereum Contracts are

EVM code + Persistent Storage

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Ethereum Contracts are

EVM code + Persistent Storage

EthereumVirtualMachine

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Every time a contract execution is initiated:

A fresh new VM singleton is instantiated

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Every time a contract execution is initiated:

A fresh new VM singleton is instantiated

The contract's code is loaded into ROM

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Every time a contract execution is initiated:

A fresh new VM singleton is instantiated

The contract's code is loaded into ROM

The contract's storage is loaded into RAM

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Every time a contract execution is initiated:

A fresh new VM singleton is instantiated

The contract's code is loaded into ROM

The contract's storage is loaded into RAM

A usual raft of VM components are initialized: PC, memory, stack, message data, etc

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

EVM opcodes are tailored to Ethereum's specific set-up:0x00: STOP0x01: ADD0x02: MUL0x03: SUB0x04: DIV0x05: SDIV0x06: MOD0x07: SMOD0x08: ADDMOD0x09: MULMOD0x0A: EXP0x0B: SIGNEDEXTEND0x10: LT0x11: GT0x12: SLT0x13: SGT0x14: EQ0x15: ISZERO0x16: AND

0x17: OR0x18: XOR0x19: NOT0x1A: BYTE0x20: SHA30x30: ADDRESS0x31: BALANCE0x32: ORIGIN0x33: CALLER0x34: CALLVALUE0x35: CALLDATALOAD0x36: CALLDATASIZE0x37: CALLDATACOPY0x38: CODESIZE0x39: CODECOPY0x3A: GASPRICE0x3B: EXTCODESIZE0x3C: EXTCODECOPY0x40: BLOCKHASH

0x00: STOP0x01: ADD0x02: MUL0x03: SUB0x04: DIV0x05: SDIV0x06: MOD0x07: SMOD0x08: ADDMOD0x09: MULMOD0x0A: EXP0x0B: SIGNEDEXTEND0x10: LT0x11: GT0x12: SLT0x13: SGT0x14: EQ0x15: ISZERO0x16: AND

0x41: COINBASE0x42: TIMESTAMP0x43: NUMBER0x44: DIFFICULTY0x45: GASLIMIT0x50: POP0x51: MLOAD0x52: MSTORE0x53: MSTORE80x54: SLOAD0x55: SSTORE0x56: JUMP0x57: JUMPI0x58: PC0x59: MSIZE0x5A: GAS0x5B: JUMPDEST0x6X: PUSHX0xF0: CREATE

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Many tools and several compilers have been created to help write Ethereum contracts to skip the need to code in assembler.

Today I will focus on the Solidity programming language, which can be compiled using:

the solc executable online at https://chriseth.github.io/browser-solidity using the geth javascript consoleimplicitly in the alethzero/alethone GUI orintrinsically in the Mix IDE

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Make money at home – create your own currency

contract token { mapping (address => uint) public coinBalanceOf; event CoinTransfer(address sender, address receiver, uint amount);

/* Initializes contract with initial supply tokens to the creator of the contract */ function token(uint supply) { coinBalanceOf[msg.sender] = (supply || 10000); }

/* Very simple trade function */ function sendCoin(address receiver, uint amount) returns(bool sufficient) { if (coinBalanceOf[msg.sender] < amount) return false; coinBalanceOf[msg.sender] -= amount; coinBalanceOf[receiver] += amount; CoinTransfer(msg.sender, receiver, amount); return true; }} Code example by

Alex Van De Sande

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Cryptographically Signed Instructions

State Data

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Ethereum“daemon”

Instructions

State Data

ÐΞVp2pEthereumInterface

Instructions

State Data

JSON RPC

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Ethereum“daemon”

Instructions

State Data

ÐΞVp2pEthereumInterface

Instructions

State Data

JSON RPC

Ideally: local machine via http

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Ethereum“daemon”

Instructions

State Data

ÐΞVp2pEthereumInterface

Instructions

State Data

JSON RPC

Web browser(e.g. Mist)

Alethzero/Alethone

Eth (C++) Geth (Go)

Pythereum (Python)

Also: Java, Javascript, Haskell …

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

JSON RPC example:

// Requestcurl -X POST --data '{"jsonrpc":"2.0","method":"eth_getBalance","params":["0x407d73d8a49eeb85d32cf465507dd71d507100c1", "latest"],"id":1}'

// Result{ "id":1, "jsonrpc": "2.0", "result": "0x0234c8a3397aab58" // 158972490234375000}

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Problem:

If anyone can upload contracts and anyone can have them be executed, DDOSing the network becomes trivial.

Solution:

Anti-spam payment token required for running contract code.

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Problem:

If anyone can upload contracts and anyone can have them be executed, DDOSing the network becomes trivial.

Solution:

Anti-spam payment token required for running contract code.

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Ether buys GAS to fuel the EVM

Every opcode instruction executed by the EVM uses up Gas.

https://openclipart.org/detail/83173/tsdpetrol-pump

MULADDSHA3

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Ether buys GAS to fuel the EVM

Every opcode instruction executed by the EVM uses up Gas.

If the VM instance runs out of Gas then execution stops.

https://openclipart.org/detail/226524/fuel-gauge

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Ether buys GAS to fuel the EVM

An amount of Gas is bought using ether when the instruction to execute a contract's code is accepted by the Ethereum network,

and given to the VM that is created to fulfill the instruction.

Only if execution completes successfully are the effects of the execution saved.

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Transfer Funds

Run Contract

New Contract

CL

IEN

TS

balances statestaten-1

staten

Tra

nsac

tion

Poo

l

Po

W

balances state

verify

execute

select

Pro

cess

Lis

t

gas

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

CL

IEN

TS

Tra

nsac

tion

Poo

l

UTXOsblockn-1

UTXOsblockn

select

Classic Blockchains

verify

Po

W

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Ethereum is explicitly state-based

Blocks record state-updates.

This makes efficiencies, such as state-pruning, much easier and more effective.

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

So what is Ethereum good for?

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Taxi image: www.nyc.govBusinessman image: openclipart.org/detail/19483/businessman-on-phoneDollar sign: openclipart.org/detail/167795/money-20Location marker: openclipart.org/detail/166612/google-places

Example: taxi escrow contract

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Taxi Escrow Taxi Escrow Taxi Escrow

Example: taxi escrow contract

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

Taxi Escrow Taxi Escrow Taxi Escrow

Example: taxi escrow contract

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0

THE WORLD COMPUTER

DEVIEW 2015-09-15 aeron.buchanan@ethereum.org Aeron Buchanan, V1, CC BY-SA 3.0