Block Chain¶

block chain on bitcoin

既然選更長的分支，那我用很低的難度去求解怎麼辦?

客戶端在眾多分支中找到符合當前難度且最長的。

欄位介紹¶

{
"hash":"000000000000000000011f35a721c6065b447eef96640ce0ca9ba9a98edd9a26",
"size":986803,
"height":494333,
"version":536870912,
"merkleroot":"eb60eac626c77e2719621f3d2bc5379f43f5a62b5994e184520eb290bb31960c",
"tx":["..........."],
"time":1510663787,
"nonce":3267589382,
"bits":"1800ce4b",
"difficulty":1364422081125.1475,
"chainwork":"000000000000000000000000000000000000000000b09e2108dc9f58fa17f83e",
"confirmations":9,
"previousblockhash":"0000000000000000001072fdaa28f5b128009e8580f6080ca82063f9a912cbbc","nextblockhash":"0000000000000000000960da72f18edad9d101fb5c3a2ac1ecbfea7600d82575",
"reward":12.5,
"isMainChain":true,
"poolInfo":{"poolName":"AntMiner","url":"https://bitmaintech.com/"}}

hash¶

Block hashing algorithm

hash256(hash256(Version+hashPrevBlock+hashMerkleRoot+Time+Bits+Nonce))

Field	Purpose	Updated when...	Size (Bytes)
Version	Block version number	You upgrade the software and it specifies a new version	4
hashPrevBlock	256-bit hash of the previous block header	A new block comes in	32
hashMerkleRoot	256-bit hash based on all of the transactions in the block	A transaction is accepted	32
Time	Current timestamp as seconds since 1970-01-01T00:00 UTC	Every few seconds	4
Bits	Current target in compact format	The difficulty is adjusted	4
Nonce	32-bit number (starts at 0)	A hash is tried (increments)	4
https://en.bitcoin.it/wiki/Block_hashing_algorithm

Warning

The output of blockexplorer displays the hash values as big-endian numbers
but python3 hashlib is little end

CODE on Python3

'''
source
support blockexplorer & blockchain
https://blockexplorer.com/api/block/000000000000000000011f35a721c6065b447eef96640ce0ca9ba9a98edd9a26
or
https://blockchain.info/rawblock/000000000000000000011f35a721c6065b447eef96640ce0ca9ba9a98edd9a26
'''
import hashlib
import codecs
import struct

'''
import hashlib using "little-end" but blockexplorer is "biggest-end" ,we need convert biggest-end to little-end
'''
def btol(st):
    if len(st)%2 !=0:
        return "error need 2 pair"
    else:
        ans=""
        for i in range(int(len(st)/2)):
            index=i*2
            ans=st[index]+st[index+1]+ans
        return ans
''' we can get sample on blockexplorer '''    
Version="536870912" #4bytes so need 8 hex
hashPrevBlock="0000000000000000001072fdaa28f5b128009e8580f6080ca82063f9a912cbbc"#32bytes
hashMerkleRoot="eb60eac626c77e2719621f3d2bc5379f43f5a62b5994e184520eb290bb31960c"#32bytes
Time="1510663787"#4bytes
Bits="1800ce4b"#4bytes
Nonce="3267589382"#4bytes

control=input("blockexplorer.com Data input \"1\" blockchain.info Date input \"2\" \n")

if control.isdecimal():
    if int(control)==1:
        pass
    elif int(control)==2:
        Bits=str(hex(int(Bits))[2:]).zfill(8)
    else:
        print("error please input 1 or 2")
        exit(1)
else:
    print("error please input 1 or 2")
    exit(1)

header_hex = (
btol(str(hex(int(Version))[2:]).zfill(8)) +
btol(hashPrevBlock) +
btol(hashMerkleRoot) +
btol(str(hex(int(Time))[2:]).zfill(8)) +
btol(Bits) +
btol(str(hex(int(Nonce))[2:])).zfill(8))



header_bin = codecs.decode(header_hex, "hex")
hash = hashlib.sha256(hashlib.sha256(header_bin).digest()).digest()


'''we want to view biggest-end'''
print("view hash by big-endian")
print (codecs.encode(hash[::-1], "hex"))

size¶

Size (bytes)

height¶

代表前面有多少塊block chain ,創世第一個blockchain的hight值為零

version¶

Block version number You upgrade the software and it specifies a new version 4bytes

merkleroot¶

$H_{A} = SHA_{256}(SHA_{256}(Tx A))$

$H_{AB} = SHA_{256}(SHA_{256}(H_{A}+H_{B}))$

tx(Transactions)¶

交易訊息

time¶

Current timestamp as seconds since 1970-01-01T00:00 UTC

nonce¶

Warning

nonce只有4bytes並不代表只需要 $2^{32}$ 就可以破解sha256
有可能算完還找不到答案,就必須更改其他欄位好讓hash符合規定

bits¶

bits to target

solution1¶

bits mean

like 0x1d00ffff
all large is 32 bytes
* 0x $\color{blue}{1d}$ --- $(1d)_{16}=(26)_{10}$ so we know 26 bytes after 00ffff
* 0x $\color{red}{00ffff}$ --- target prefix
$000000\color{red}{00ffff}\color{blue}{0000000000000000000000000000000000000000000000000000}$

solution2¶

better performence

exponent=bits[0~1]

coefficient=bits[2~7]

target = coefficient * 2^(8 * (exponent – 3))

CODE on Python3

bite to target
solution1

1 2	bits="1d00ffff" print(bits[2:].ljust(2*int(bits[0:2],16),'0').zfill(64))

solution2

1	print(hex(0x00ffff2(8(0x1d - 3)))[2:].zfill(64))

difficulty¶

公式

兩種difficulty 一般使用bdiff
bdiff 定義:1困難度（difficulty）的bits=0x1D00FFFF
pdiff-target:0x00000000FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
$1=\frac{f_{conv}(0x1D00FFFF)}{f_{conv}(0x1D00FFFF)}$
exponent=bits[0-1]
coefficient=bits[2-7]

$f_{conv}(bits)$ =coefficient * 2^(8 * (exponent – 3))
$f_{conv}(\color{red}{1D}\color{blue}{00FFFF})=\color{blue}{00FFFF}_{16} * 2^{( 8 *( \color{red}{1D}_{16} - 3 ))}$
$difficulty=\frac{f_{conv}(0x1D00FFFF)}{f_{conv}(bits) }$

target mean

$target=f_{conv}(bits)$
target意思就是在挖礦的時候nonce該怎麼調整好讓hash target 越小代表難度越大

we know bits=1800ce4b difficulty(bdiff)=?

1	difficulty=0x00ffff2(8(0x1d - 3))/float(0x00ce4b2(8(0x18 - 3)))

Answer:difficulty=1364422081125.1475

Bitcoin Difficulty

chainwork¶

範例

set chainwork=10Hash 你的電腦1H/s 代表你要算玩這串區塊練區要10秒

confirmations¶

Confirmation 代表該blockchain的版本之下前面有多少塊block 一般來說等待6塊就可以確認交易

previousblockhash¶

前一個區塊鏈的HASH

reward¶

算出該區塊練所給的獎勵
2009~2012 50BTC
2013~2016 25BTC
2017~2020 12.5BTC
2020~ 6.25BTC

isMainChain¶

是不是最長的那個區塊練

poolInfo¶

礦場資訊

mining¶

example "bits":"1800ce4b"

$target=(0x00ce4b)_{16} * 2^{(8 * ((0x18)_{16} – 3))}$

Note

我們想要藉由更動nonce 來讓hash<target

target=000000000000000000CE4B000000000000000000000000000000000000000000
hash= 000000000000000000011f35a721c6065b447eef96640ce0ca9ba9a98edd9a26

Hash Rate¶

計算駭客要攻擊51%的難度

硬體參考數據
 Hashrate
注意：該換算只能參考用
Intel Xeon E5-2698 V4 $\simeq$ 800H/s
Intel Xeon Phi 7210 $\simeq$ 600H/s
天和二號
32,000顆Xeon E5主處理器和48,000個Xeon Phi協處理器
天和二號:800*32,000+48,000*600=54400000H/s=54400000MH/s=54400GH/s
全球比特幣Hashrate：7602699877 GH/s
全球比特幣/天和二號=139755
結論需要13/2萬組天和二號超級電腦才能超過51%全世界的電腦
由於目前比特幣是使用ASIC所以效能才會如此之大是cpu所無法批擬

256/8 32bytes