[213] ethereum

DEVIEW 2015-09-15 [email protected] Aeron Buchanan, V1, CC BY-SA 3.0

THE WORLD COMPUTER


"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


The computer that anyone can program and everyone can trust


A planetary-scalevirtual machine:

Trusted Computation and Storage Service Platform


Peer-to-peer network:


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


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


Intrinsic features include:

Cryptographic Identity Checking and Custom Payment Logic


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


Ethereum Contracts are

EVM code + Persistent Storage


Ethereum Contracts are

EVM code + Persistent Storage

EthereumVirtualMachine


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





The contract's storage is loaded into RAM

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


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


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

https://chriseth.github.io/browser-solidity


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


Cryptographically Signed Instructions

State Data


Ethereum“daemon”

Instructions

State Data

ÐΞVp2pEthereumInterface

Instructions

State Data

JSON RPC



Instructions

State Data


Instructions

State Data

JSON RPC

Ideally: local machine via http



Instructions

State Data


Instructions

State Data

JSON RPC

Web browser(e.g. Mist)

Alethzero/Alethone

Eth (C++) Geth (Go)

Pythereum (Python)

Also: Java, Javascript, Haskell …


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}


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.


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



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



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.


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


CL

IEN

TS

Tra

nsac

tion

Poo

l

UTXOsblockn-1

UTXOsblockn

select

Classic Blockchains

verify

Po

W


Ethereum is explicitly state-based

Blocks record state-updates.

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


So what is Ethereum good for?


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

http://www.nyc.gov/

http://openclipart.org/detail/19483/businessman-on-phone

https://openclipart.org/detail/167795/money-20

https://openclipart.org/detail/166612/google-places


Taxi Escrow Taxi Escrow Taxi Escrow

Example: taxi escrow contract


THE WORLD COMPUTER

[213] ethereum

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