基于区块链的安全协议设计

Blockchain & e-voting Introduction to Blockchain

12Blockchain &cryptocurrency

3Blockchain &PDP 4Road

map

Conclusion

5

1 Introduction to Blockchain

Blockchain

• A chain of blocks

•Public ledger/database

•Records all transactions across P2P network •Shared between participants

•How Blockchain works?

-example…

Public Decentr

alized Distribu

ted

Immuta

ble

Can not be tampered

Approved by most peers

No central party

Publicly accessible

Main features

Four characterized elements

Components Record source, destination, amounts,etc…Transaction Block Blockchain A chain of blocks

A list of transactions

trans:H()prev:H()trans:H()prev:H()

trans:H()

prev:H()H()H()

H()H()H()H()

transaction transaction transaction transaction

Components

trans:H()

prev:H()trans:H()prev:H()

trans:H()prev:H()H()H()

H()H()H()H()

transaction transaction transaction transaction

transaction Block Blockchain

Components

******

Traditional blockchain protocols were designed with script language

make a protocols like this

or Blockchain2.0----Ethereum

Ethereum

•Blockchain with expressive programming language

–Programming language makes it ideal for smart

contracts(Turing-complete)

• A smart contract is a computer program executed in a secure environment that directly controls digital assets –Most public blockchains are for

cryptocurrencies (Can only transfer coins

between users)

–Smart contracts enable much more applications

Difference: Bitcoin vs Ethereum •“A Peer-to-Peer Electronic Cash System”•Satoshi Nakamoto(Pseudonymous)•Intentionally-limited scripting language •UTXO-based framework

•Released January 3,2009

•10 minutes block time

Difference: Bitcoin vs Ethereum •“Generalized state-transition machine”•Vitalik Buterin (co-founder of Bitcoin Magazine)•Turing-complete programming language •Account-based framework

•Released July 30,2015

•15-second block time

E n e r g y Shippin g Government Healthcare Financ e

Cryptocurrency

Blockchain Insurance Trading Key management Manusfacturing Voting

IoT Transportation Funding S m a r t C o n t r a c t

2 Blockchain &cryptocurrency

•Thousands of cryptocurrencies are launched •Various features and demands

•Top 2: Bitcoin &Ethereum

Bitcoin privacy

•The block chain is a history of every Bitcoin transaction ever!

•Identifiers are public keys not names(“pseudonyms”)•You can make as many public keys as you want

•But these still leak information!