PythonCurrency/BlockChain.py at main · BlckChainDev/PythonCurrency · GitHub

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#BlockChain.py
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import hashes


class someClass:
    string = None
    num = 328965
    def __init__(self, mystring):
        self.string = mystring
    def __repr__(self):
        return self.string + "^^^" + str(self.num)

class CBlock:
    data = None
    previousHash = None
    previousBlock = None
    def __init__(self, data, previousBlock):
        self.data = data
        self.previousBlock = previousBlock
        if previousBlock != None:
            self.previousHash = previousBlock.computeHash()
    def computeHash(self):
        digest = hashes.Hash(hashes.SHA256(), backend=default_backend())
        digest.update(bytes(str(self.data),'utf8'))
        digest.update(bytes(str(self.previousHash),'utf8'))
        return digest.finalize()
    def is_valid(self):
        if self.previousBlock == None:
            return True
        return self.previousBlock.computeHash() == self.previousHash

if __name__ == '__main__':
    root = CBlock('I am root', None)
    B1 = CBlock(b'I am a child.', root)
    B2 = CBlock('I am B1s brother', root)
    B3 = CBlock(12354, B1)
    B4 = CBlock(someClass('Hi there!'), B3)
    B5 = CBlock("Top block", B4)

    for b in [B1, B2, B3, B4, B5]:
        if b.is_valid():
            print ("Success! Hash is good.")
        else:
            print ("ERROR! Hash is no good.")

    B3.data=12345
    if B4.is_valid():
        print ("ERROR! Couldn't detect tampering.")
    else:
        print ("Success! Tampering detected.")

    print(B4.data)
    B4.data.num = 99999
    print(B4.data)
    if B5.is_valid():
        print ("ERROR! Couldn't detect tampering.")
    else:
        print ("Success! Tampering detected.")