Intro to Cryptocurrencies and Smart Contracts

Day 2

Ethan Buchmanethan@coinculture.info

Aug 20 2017 Toronto

Contents

- Blockchain Platforms- Bitcoin- Ethereum- Tendermint

Blockchain Platforms

Public Cryptocurrencies: Proof of Work

Public Cryptocurrencies: Proof of Stake

Public Cryptocurrencies: App Coins

Public Cryptocurrencies: Storage Coins

Public Cryptocurrencies: Tomorrow

Blockchain Platforms

Bitcoin

Addresses

http://www.righto.com/2014/02/bitcoins-hard-way-using-raw-bitcoin.html

Transactions

Transactions

Transaction Scripts

- Output: scriptPubKey- conditions that must be met to spend

these outputs

- Input: scriptSig- data satisfying the conditions of the

scriptPubKey

Transaction Scripts - P2PKH

Pay-2-Pubkey-HashscriptPubKey: OP_DUP OP_HASH160 <pubKeyHash> OP_EQUALVERIFY OP_CHECKSIG

scriptSig: <sig> <pubKey>

https://blockchain.info/tx/cadbe6ea2bdc089f7093d532cecdd10dde69c124722b35a009538497536e80a7

Transaction Scripts - P2PKH

Pay-2-Pubkey-HashscriptPubKey: OP_DUP OP_HASH160 <pubKeyHash> OP_EQUALVERIFY OP_CHECKSIG

scriptSig: <sig> <pubKey>

https://blockchain.info/tx/9f456b95ea97cfc9dcb6eec6c5d42afef2974b49517894251fba974ad1fd5910

Transaction Scripts - P2PKH

Transaction Scripts - MultiSig

MultiSigscriptPubKey: <m> <A pubkey> [B pubkey] [C pubkey...] <n> OP_CHECKMULTISIG

scriptSig: OP_0 <A sig> [B sig] [C sig...]

https://blockchain.info/tx/59609f66c65c85c2990ed5699275e99eb9af358dece111107eddbed02100cb34

Transaction Scripts - MultiSig

MultiSigscriptPubKey: <m> <A pubkey> [B pubkey] [C pubkey...] <n> OP_CHECKMULTISIG

scriptSig: OP_0 <A sig> [B sig] [C sig...]

https://blockchain.info/tx/a1dd1e764940543e7ca53a05f7c15e7ca1b35a88dac82802cf4a19db77340e8e

Transaction Scripts - P2SH (Multisig)

Pay-2-Script-HashscriptPubKey: OP_HASH160 <Hash160(redeemScript)> OP_EQUAL

scriptSig: <sig> [sig] [sig...] <redeemScript>

https://blockchain.info/tx/5fb8e21e4e5d0557f0bb6ec3d8c4f4b7968e39c9c3d1af486322c3098ae633a3

Transaction Scripts - P2SH (Multisig)

Pay-2-Script-HashscriptPubKey: OP_HASH160 <Hash160(redeemScript)> OP_EQUAL

scriptSig: <sig> [sig] [sig...] <redeemScript>

https://blockchain.info/tx/24c5a606501655c00345c485fb11771103d95e15bffe3e2f10c62fa66bead654https://chainquery.com/bitcoin-api/decodescript

Transaction Scripts - P2SH (CSV)

OP_IF 2 <pubkey1> <pubkey2> 2 OP_CHECKMULTISIG

OP_ELSE10 OP_CHECKSEQUENCEVERIFY OP_DROP OP_DUP OP_HASH160 <addr> OP_EQUALVERIFY OP_CHECKSIG

OP_ENDIF

Redeem condition 1: https://blockchain.info/tx/3fa26dc97735f657bdf997360b3de698e1e8b92f4dc88193a38be926ff183e0c

Redeem condition 2: https://blockchain.info/tx/4ba75dfe11988663cfcbbc8911eedee1f867d99fa744a6137e885315b3a073e1

https://chainquery.com/bitcoin-api/decodescript

Transaction Scripts - Embedding Data

OP_RETURNscriptPubKey: OP_RETURN <data>

scriptSig: N/A

https://blockchain.info/tx/d29c9c0e8e4d2a9790922af73f0b8d51f0bd4bb19940d9cf910ead8fbe85bc9b

Transaction Scripts - Embedding Data

https://blockchain.info/address/35ty8iaSbWsj4YVkoHzs9pZMze6dapeoZ8

Transaction Scripts - Craziness

https://blockchain.info/tx/9f17f3ce43019c24baa6d679edfdddeada856f617cd9c1f6008d49be4542b768

https://blockchain.info/tx/219b5815886af9c9ff74fdbe8146731534b0c1b1dc23bfd3fab81745433bbc3f

Tools (Electrum and BitcoinJS)

Ethereum

Storing State: Accounts

- Accounts are:- Address- Balance- Nonce- Bytecode- Storage

Ether. The ethereum cryptofuel

# of transactions sent. Avoid replay attacks and the mess of inputs/outputs

Turing complete EVM assembly language.32-byte word stack, byte-array memory

32-byte word storage area. Isolated per account

Last 20 bytes of the hash of the pubkey

Storing State

Transactions

Nonce

Data

Value

To

Gas Limit

Gas Price

Sender’s transaction count

The product of these is the fee paid

Destination address. Can be a contract or another account

Amount of ether being sent

Data to be processed by a contract

Contracts

Code Storage

Calldata Stack Memory

Non-volatile

Volatile

Nonce

Data

Value

To

Gas Limit

Gas Price

Contracts

Code Storage

Calldata Stack Memory

Contracts

Code Storage

Calldata Stack Memory

Transactions

Contract Calls (“Internal Transactions”)

Contract Code

https://etherscan.io/address/0x6090a6e47849629b7245dfa1ca21d94cd15878ef

Contract State

https://etherscan.io/address/0x6090a6e47849629b7245dfa1ca21d94cd15878ef

Contract Events

Deploying Contracts

https://etherscan.io/tx/0x4c3fd67575a9254c553d906af0f2c84789502bae5a6723ea3bc345c5dcbf0751

Interacting with Contracts

https://www.myetherwallet.com/#contracts

Contract Notes

- Thoughts on Solidity: https://news.ycombinator.com/item?id=14691212- Guide: https://github.com/CoinCulture/evm-tools/

- Security:- Basics: https://blog.ethereum.org/2016/06/10/smart-contract-security/- The Docs: http://solidity.readthedocs.io/en/develop/security-considerations.html- Extensive Guide: https://github.com/ConsenSys/smart-contract-best-practices- Contract Framework: https://github.com/OpenZeppelin/zeppelin-solidity- Analysis: http://hackingdistributed.com/2016/06/16/scanning-live-ethereum-contracts-for-bugs/

- Post Mortems- Parity Wallet Bug: http://hackingdistributed.com/2017/07/20/parity-wallet-not-alone/- King of the Ether: http://www.kingoftheether.com/postmortem.html- Quadriga:

https://www.reddit.com/r/ethereum/comments/6ettq5/statement_on_quadrigacx_ether_contract_error/

Tools (MyEtherWallet, Truffle, Web3.JS)

Tendermint

The Problem

Byzantine Fault Tolerant State Machine Replication

in Any Programming Language

Somebody else’s state machine

- Zookeeper, etcd, consul- Fancy key-value store- Emphasis on distributed systems tasks (dynamic config, locking,

etc.)

- Bitcoin- “Programmable money”- “Functional programming” - no state (!), contracts renewed

every transaction- Forth like, purposefully not Turing-complete

- Ethereum- “Smart contracts”- “Contract-oriented” - stateful contracts live independently on the

blockchain- Turing complete (Ethereum Virtual Machine)

Application Blockchain Interface

SECURITY & NETWORKING PLATFORMS

APPLICATION PLATFORMS

SOCKET PROTOCOLSCGI ABCI

Tendermint

Tendermint

ABCI

- Network of “validators”, each with private key

- Validators take turns (round-robin) proposing blocks of recent transactions

- Validators vote on proposed blocks

- Once more than ⅔ vote for same block, it is committed

- Transactions in committed blocks are run against the application to get a final checksum included in the next block

ABCI

ABCI

ABCI

Tendermint

Cosmos Network (Scalable Cryptocurrency)

https://cosmos.network

More on Tendermint

https://tendermint.com

https://cosmos.network

https://github.com/tendermint/tendermint

Tendermint in a Nutshell

https://medium.com/@tendermint/tendermint-in-a-nutshell-39d9f7f66ad7

Fin

presents