BlockChain implementation by python

BlockChain on Python
한국폴리텍대학(Korea Polytechnics)
스마트금융과(dept. of Smart Finance)

Overview
 Characteristics of blockchain
 Python
 Simple Http Server by Python
Make your own code and APIs
 Block, Hashing
 Transaction
Design your transaction model
 Making Block
 Merge with your BlockChain and Http Server
 Propagating Block to other nodes

Characteristic of BlockChain
 Transactions
 Blocks
 Snapshot or Chaining between Blocks
 Hash for a integrity
 Validating of existing Blocks
 Interface or Interact with other nodes
 etc…

Python
development environment
 Python
 Anaconda
 Jupyter
 Pycharm
 Ftp, Linux Server, REST Test Tool(ARC, Post Man, Fiddler,…)
 Git, File Compare Tools …

Simple HTTP Server
by Python (GET)
참조 : https://mafayyaz.wordpress.com/2013/02/08/writing-simple-http-server-in-python-with-rest-and-json/
참조 : https://docs.python.org/3/library/http.server.html?highlight=basehttprequesthandler#http.server.BaseHTTPRequestHandler

Simple HTTP Server
by Python (GET) – Review
 python 문자열 다루기 : split

Simple HTTP Server
by Python (GET) – Review
 좀 더 Python 한 방법은?

Practice #1
 사용자가 요청한 주소의 Query String을 분해하여 HTML로 리턴하시오.
예>
http://localhost:8080/api/v1/getrecord?city=seoul&zipcode=08206&mobile=01012341234&nickname=cat
위 요청에 대한 응답 (HTML)
city : seoul
zipcode : 08206
mobile : 01012341234
nickname : cat

Practice #2
 서버에서 python socket serve를 실행하자
 포트 번호 : 80 + 학번 끝 두자리로 설정
 116번 서버에 본인 작업 디렉토리에서 소켓 서버를 실행하고
http://192.168.110.116:80xx/api/v1/ping 을 호출했을 때 본문없이 200 응답을 리턴
예시> 학번 끝자리가 23번인 학생의 경우
본인의 소켓서버를 116번 서버의 /home/smrt0023/ 폴더에 업로드 
소켓서버를 실행(포트번호는 8023) 
교수가 http://192.168.110.116:8023/api/v1/ping 을 호출했을때 200 OK 응답을 주면 성공

Fiddler로 테스트하기
GET POST(application/json) POST(form based)

Postman 설치
 [H/W] 크롬 웹스토어에서 postman 으로 검색하고 설치 & 테스트

Simple HTTP Server
by Python (POST)
application/json;encode=utf-8
ctype pdict

Simple HTTP Server
by Python (POST)

Practice #3
 Make your own APIs on Development Server
 포트 번호 : 80 + 학번 끝 두자리로 설정
 API Spec 작성 및 테스트 결과를 Development Server에 업로드
- 업로드 위치 : /home/smrt00xx/…
- 실행 : python 000.py
- 테스트 : http://192.168.110.116:80xx/api/v1/addrecord
- API Spec. : API기본정보(요청URL, 포맷, 방식), 요청변수, 출력결과, 에러코드

Practice #3 (Cont.)
항목 정보 비고
요청URL http://192.168.110.116:80XX/api/v1/addrecord
요청Format JSON 형식
예> {“key1": [“value1",“value2"], “key2": “value1"}
요청Method POST
출력Format 입력요청한 JSON을 코드소유자 정보 추가하여 리턴
예> {“key1": [“value1",“value2"], “key2": “value1“, author:hwy}
결과code 성공시 200
실패시 403
…
 API Specification 예시

blockchain implementation on
python

Genesis Block
 6 Attributes
• Index – it’s position in the blockchain
• Previous Hash – the hash of the block that came before the current block
• Timestamp – the time the block was created
• Data – the information (e.g. transactions) that the block carries
• Hash – the hash of the block itself.
• proof – proof of work

블록의 구조
class Block:
#A basic block contains, index (blockheight), the previous hash, a timestamp, tx information, a nonce, and the current hash
def __init__(self, index, previousHash, timestamp, data, proof, currentHash):
self.index = index
self.previousHash = previousHash
self.timestamp = timestamp
self.data = data
self.currentHash = currentHash
self.proof = proof
출처 : http://blockxchain.org/2017/06/04/simple-local-python-blockchain-pt1/
블록의 높이
거래 데이터
블록생성시점
이전블록의 해쉬값(이전블록의 연결고리, 스냅샷)
현재 블록의 해쉬값
작업증명 값( XX횟수)

블록데이터 리턴
 Sequence Diagram
readBlockchain
블록체인 DB가 존재한다면?
if yes, DB를 읽어서 return
else 빈 데이터를 return

Source Code
블록체인 DB가 존재 X
빈 데이터를 return

At the moment,
블록데이터가 없는 상황
 블록데이터 생성이 필요
 신규API를 생성하여 Genesis Block을 생성해야 함
~/block/generateBlock를 추가하자
 블록을 구성할 데이터(Transaction Data)는 어떻게 구성할 것인가?
일단은, 임시 랜덤데이터를 구성하자
transaction = 'UserID ' + str(txFrom) + " sent " + str(amount) + ' bitTokens to UserID ' + str(txTo) + ". “
차후, 개인 또는 그룹별 블록체인 비즈니스 아이디어를 반영한 트랜잭션으로 수정예정

Source Code
(~/block/generateBlock)
 API Interface

블록데이터 생성 흐름
getTxDatareadBlockchainmineNewBlock
else, “Genesis Block” 생성하여 return
calculateHashgenerateNewBlock writeBlockchain
해쉬값이 우리가 정한 난이도와 일치한다면?
if yes, 블록체인 기록
else, generateNewBlock 반복

mineNewBlock
def mineNewBlock(difficulty = 5, blockchainPath = 'blockchain.csv'):
blockchain = readBlockchain(blockchainPath)
txData = getTxData()
timestamp = time.time()
proof = 0
newBlockFound = False
print('Mining a block...')
while not newBlockFound:
#print("Trying new block proof...")
newBlockAttempt = generateNextBlock(blockchain, txData, timestamp, proof)
if newBlockAttempt.currentHash[0:difficulty] == '0'*difficulty:
stopTime = time.time()
timer = stopTime - timestamp
print('New block found with proof', proof, 'in', round(timer, 2), 'seconds.')
newBlockFound = True
else:
proof += 1
blockchain.append(newBlockAttempt)
writeBlockchain(blockchain)
def mine(blocksToMine = 5):
for _ in range(blocksToMine):
mineNewBlock()

def getLatestBlock(blockchain):
return blockchain[len(blockchain)-1]
def generateNextBlock(blockchain, blockData, timestamp, proof):
previousBlock = getLatestBlock(blockchain)
nextIndex = int(previousBlock.index) + 1
nextTimestamp = timestamp
nextHash = calculateHash(nextIndex, previousBlock.currentHash, nextTimestamp, proof, blockData)
return Block(nextIndex, previousBlock.currentHash, nextTimestamp, blockData, proof, nextHash)
배열
generateNextBlock

def calculateHash(index, previousHash, timestamp, data, proof):
value = str(index) + str(previousHash) + str(timestamp) + str(data) + str(proof)
sha = hashlib.sha256(value.encode('utf-8'))
return str(sha.hexdigest())
Hash 대상 : 현재 블록의 인덱스 + 이전 블록의 Hash + 현 블록의 TimeStamp + 현 블록의 거래데이터 + PoW(#)
calculateHash

Genesis Block
 Now we can create genesis block.
def getGenesisBlock():
timestamp = time.time()
print("# timestamp를 찍어본다.")
print("time.time() => %f n" % timestamp)
tempHash = calculateHash(0,'0',timestamp,"My very first block",0)
print(tempHash)
return Block(0, '0', timestamp, "My very first block", 0, tempHash)
blockchain = [getGenesisBlock()]
DB에 생성된 블록이 없을 경우 호출됨
현 블록의 해쉬값을 생성
(index, previousHash, timestamp, data, proof)

블록체인 데이터 조회하기
 블록데이터 조회
~/block/getBlockData로 조회하자

So far we can
 Create a genesis block
 Hash blocks
 Create additional blocks

Practice #3
 Design Your Own Transaction Data

이제 검증을 위한 API를 추가해 봅시다.
 검증로직 설계
 신규API를 생성하여 검증대상인 블록체인 데이터를 받아야 함(POST)
~/block/validateBlock/를 추가하자
- input과 output은 어떻게 설계해야 하는가?

Validation Blocks

Validation Blocks
def isValidChain(bcToValidate):
genesisBlock = []
bcToValidateForBlock = []
# Read GenesisBlock
try:
with open('blockchain.csv', 'r') as file:
blockReader = csv.reader(file)
for line in blockReader:
block = Block(line[0], line[1], line[2], line[3], line[4], line[5])
genesisBlock.append(block)
break
except:
print("file open error in isValidChain")
pass
# transform given data to Block object
for line in bcToValidate:
# print(type(line))
# index, previousHash, timestamp, data, currentHash, proof
block = Block(line['index'], line['previousHash'], line['timestamp'], line['data'], line['currentHash'], line['proof'])
bcToValidateForBlock.append(block)
#if it fails to read block data from db(csv)
if not genesisBlock:
print("fail to read genesisBlock")
return False
# compare the given data with genesisBlock
if not isSameBlock(bcToValidateForBlock[0], genesisBlock[0]):
print('Genesis Block Incorrect')
return False
tempBlocks = [bcToValidateForBlock[0]]
for i in range(1, len(bcToValidateForBlock)):
if isValidNewBlock(bcToValidateForBlock[i], tempBlocks[i - 1]):
tempBlocks.append(bcToValidateForBlock[i])
else:
return False
return True
CSV REST Call
Genesis
Block
Genesis
Block
=

Practice #4
 Design Post API of a new transaction data

Transaction Data
 As-Is Transaction Data (5 random data)
“UserID <random number> sent <random number> bitTokens to UserID <random number>.”
 To-Be Transaction Data
index currentHash timestamp transaction data
<<Block>>
<<Transactions>>
commitYN sender amount receiver UUID(unique #)
채굴포함여부

class txData
 5 attributes
블록 포함여부(채굴) : commitYN
송신자 : sender
금액 : amount
수신자 : receiver
고유식별값 : uuid
class txData:
def __init__(self, commitYN, sender, amount, receiver, uuid):
self.commitYN = commitYN
self.sender = sender
self.amount = amount
self.receiver = receiver
self.uuid = uuid

POST API 추가하기
(transaction data)

Transaction Data
(Dictionary  Instance of class txData)
import uuid 필요
예> 369a1e95-3723-4b26-8ab8-9bcc2c5938f0

Write
Transaction
Data
<<temp csv>><<txData csv>>
new tx data
<<temp csv>> <<txData csv>>

getTxData 수정
예> [6b3b3c1e-858d-4e3b-b012-8faac98b49a8]UserID hwang sent 333 bitTokens to UserID kim.

Update txData of csv #1
(when it has been mined)
 채굴되었다면?

Update txData of csv #2
정규표현식
row[4]row[0]

Practice #5
 Design Post API of a sending transaction data

set up
 library, global variables
타 노드로 채굴 정보를 POST하기 위한 라이브러리
노드간 인터페이스 API
노드 정보(서버IP, Port) 를 저장하는 파일

broadcast block when it mined
타 노드로 전파

broadcastNewBlock
방금 채굴된 블록을 포함한 블록체인 정보를
인접 노드의 API(receiveNewBlock)로
POST 호출하여 전달

readNodes
노드 정보(서버IP, Port) 를 읽어오기

addNode
http://localhost:8099/node/addNode?127.0.0.1:8096

receive new block info
g_receiveNewBlock = "/node/receiveNewBlock"

compare blockchain info
 latest block +1 != broadcasted last block
latest block == broadcasted last block
latest block +1 < broadcasted last block
latest block +1 > broadcasted last block
 latest block +1 == broadcasted last block

initSvr (1/2)
 인접 노드 정보 구하기

initSvr (2/2)
 블록체인 정보 구하기
g_bcFileName = "blockchain.csv"

related sites…
 __dict__ 설명 : https://wikidocs.net/1743
 json.dump 설명 : http://pythonstudy.xyz/python/article/205-JSON-%EB%8D%B0%EC%9D%B4%ED%83%80
https://kimdoky.github.io/python/2017/11/11/library-book-chap8-4.html
https://docs.python.org/3/library/json.html
 람다식 설명 : https://wikidocs.net/64

정규표현식(Regular Expression)
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BlockChain implementation by python

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