Term 1 S3 Lesson 1: Blockchain Data Overview

Blockchain vs Traditional Databases

Blockchain as a dataset - overview

Blockchain as a dataset?
traditional database characteristics
blockchain characteristics
Traditional Database vs Blockchain

Traditional Database Characteristics

Network - Centralized
Functions - Create, Read, Update, Delete (CRUD)
Mutability - mutable (can be updated after adding to the database)
Authorization - Centralized
Transparency - Low

Blockchain Characteristics

Network - Distributed
- Pro: Control given to nodes
- Con: Must achieve consensus
Functions - Read, append and validate
- Pros: accurate historical record; faster read and write
- Con: must achieve consensus
Mutability - Immutable
- Pro: permanent historical record
- Con: storage space
Authorization - Distributed
- Pro: Extremely secure
- Con: Cannot dispute transactions
Transparency - High
- Pro: everyone has access
- Con: No permission control

Do you need a blockchain?

Blockchain Questions Overview

Do you need a database
Does it require shared write access
Will you need to create the trust between users
Canyou operate without trusted 3rd parties
Can you operate without control over permissions

(preview: 3 types of blockchains - public, private and hybrid)

Blockchain Types

public
private
hybrid: shared private network combined with not publicly available data

https://www.ibm.com/blogs/blockchain/2017/05/the-difference-between-public-and-private-blockchain/

https://hackernoon.com/3-popular-types-of-blockchains-you-need-to-know-7a5b98ee545a

Which type to use

Here are 3 questions to help you determine which type of blockchain is right for your situation.

Will transactions be public?
Will other companies need access to your data?
Should some information be public while other information is restricted?

P2P Network vs Client-Server Model Overview

Client Server Model

Client - makes requests
Server - responds to client

P2P network

network of computers that share access to files with each other

P vs C

Infrastructure: single server (corporations) vs collection of nodes (mining farms)
Cost: expensive vs cheap
Control: authority vs network
Security: high vs low
Stability: stable vs unstable

Explore Blockchain Data

Blockchain Explorer

https://blockexplorer.com/

Block - Block Header + Block Transactions

Block header: metadata about the block, including hash value
Block Transactions:
- Coinbase (aka. first transaction)
- input, output, fee, # of confirmations, # amount sent

Explore: Search block #

Explore blockchain data in JSON

Block header:

hash
confirmations
strippedsize
size
weight
height
version
versionHEX
merkleroot
tx (transaction hash values)
time
mediantime
nonce
bits
difficulty
chanwork
perviousblockhash

Block transactions:

txid
hash

vin

"vin":[
    {
        "coinbase": "039ff1072...",
        "sequence": 3579139394
    }
],

vout (some are not shown)

"vout":]{
    "value": 12.52201057
    "n": 0,
    "scriptPubKey":{"..."}
  	},{
  	"value": 0.00000000,
  	"n":1,
  	"scriptPubKey":{"..."}
}

Raw data are just hex strings

Nonce是Number once的缩写，在密码学中Nonce是一个只被使用一次的任意或非重复的随机数值。在加密技术中的初始向量和加密散列函数都发挥着重要作用，在各类验证协议的通信应用中确保验证信息不被重复使用以对抗重放攻击(Replay Attack)

https://baike.baidu.com/item/Nonce/2525414?fr=aladdin

Practice Blockchain Data

see: https://github.com/xiaozhenliu/udacity-blockchain.git

Explore Bitcoin’s Codebase

https://github.com/bitcoin/bitcoin

Genesis Block: /src/chainparams.cpp, line 20
Original Timestamp: line 54
Other Variables

BIPs and Forks

Bitcoin Improvement Proposals: Technical documents used to issue changes to the bitcoin core client
- Written by community members
- Voted on by miners
- Accepted or denied
- Implemented by developers
Forks:
- hardfork
- softfork
- source code fork

Blockchain Nanodegree Notes 20181026