lessons period 2

period_2/02-sockets/902/BlockChain.py

@@ -0,0 +1,24 @@
+from cryptography.hazmat.backends import default_backend
+from cryptography.hazmat.primitives import hashes
+
+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

period_2/02-sockets/902/Client_test.py

@@ -0,0 +1,65 @@
+from TxBlock import *
+from Transaction import *
+from Signature import *
+
+from SocketUtil import *
+
+SERVER = 'localhost'
+TCP_PORT = 5050
+
+if __name__ == "__main__":
+
+    alex_prv, alex_pbc = generate_keys()
+    mike_prv, mike_pbc = generate_keys()
+    rose_prv, rose_pbc = generate_keys()
+    mara_prv, mara_pbc = generate_keys()
+
+    Tx1 = Tx()
+    Tx1.add_input(alex_pbc, 2.3)
+    Tx1.add_output(mike_pbc, 1.0)
+    Tx1.add_output(rose_pbc, 1.1)
+    Tx1.sign(alex_prv)
+
+    Tx2 = Tx()
+    Tx2.add_input(rose_pbc, 2.3)
+    Tx2.add_input(mike_pbc, 1.0)
+    Tx2.add_output(alex_pbc, 3.1)
+    Tx2.sign(mike_prv)
+    Tx2.sign(rose_prv)
+
+    B1 = TxBlock(None)
+    B1.addTx(Tx1)
+    B1.addTx(Tx2)
+
+    server = newServerSocket(SERVER)
+    
+    print('A connection to the server is established.')
+
+    # -------------------------------------
+    sendObj(SERVER, Tx2)
+    print('Server is in Receiving mode ...')
+    Obj = recvObj(server)
+    if Obj:
+        print('Data: ', type(Obj),'\n')
+    else:
+        print('No object received')
+
+    # -------------------------------------
+    sendObj(SERVER, B1)
+    print('Server is in Receiving mode ...')
+    Obj = recvObj(server)
+    if Obj:
+        print('Data: ', type(Obj),'\n')
+    else:
+        print('No object received')
+
+    # -------------------------------------
+    print('Server is in Receiving mode ...')
+    Obj = recvObj(server)
+    if Obj:
+        print(Obj)
+    else:
+        print('No object received')
+
+    print("Success! The connection is released.")  # If returns after time, then successful
+    server.close()

period_2/02-sockets/902/Signature.py

@@ -0,0 +1,41 @@
+from cryptography.exceptions import *
+from cryptography.hazmat.primitives.asymmetric import rsa
+from cryptography.hazmat.primitives import hashes
+from cryptography.hazmat.primitives.asymmetric import padding
+from cryptography.hazmat.primitives import serialization
+
+def generate_keys():
+    private_key = rsa.generate_private_key(public_exponent=65537,key_size=2048)
+    public_key = private_key.public_key()
+
+    pbc_ser = public_key.public_bytes(
+        encoding=serialization.Encoding.PEM,
+        format=serialization.PublicFormat.SubjectPublicKeyInfo)
+    return private_key, pbc_ser
+
+def sign(message, private_key):
+    message = bytes(str(message), 'utf-8')
+    signature = private_key.sign(
+        message,
+        padding.PSS(mgf=padding.MGF1(hashes.SHA256()), salt_length=padding.PSS.MAX_LENGTH),
+        hashes.SHA256()
+        )
+    return signature
+
+def verify(message, signature, pbc_ser):
+    message = bytes(str(message), 'utf-8')
+    public_key = serialization.load_pem_public_key(pbc_ser)
+    try:
+        public_key.verify(
+            signature,
+            message,
+            padding.PSS(mgf=padding.MGF1(hashes.SHA256()),
+            salt_length=padding.PSS.MAX_LENGTH),
+            hashes.SHA256()
+            )
+        return True
+    except InvalidSignature:
+         return False
+    except:
+        print("Error executing 'public_key.verify'")
+        return False

period_2/02-sockets/902/SocketUtil.py

@@ -0,0 +1,38 @@
+import socket
+import pickle
+import select
+
+TCP_PORT = 5050
+BUFFER_SIZE = 1024
+
+
+def newServerSocket(ip_addr):
+    server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    server_socket.bind((ip_addr, TCP_PORT))
+    server_socket.listen()
+    return server_socket
+
+
+def recvObj(socket):
+    ready_to_read, ready_to_write, in_error = select.select([socket], [], [socket], 20)
+    if socket in ready_to_read:
+        print('Server is ready to receive data ...')
+        connected_socket, addr = socket.accept()
+        print('Server is receiving data ...')
+        all_data = b''
+        while True:
+            data = connected_socket.recv(BUFFER_SIZE)
+            if not data:
+                break
+            all_data = all_data + data
+        return pickle.loads(all_data)
+    return None
+
+
+def sendObj(ip_addr, obj):
+    soc = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    soc.connect((ip_addr, TCP_PORT))
+    data = pickle.dumps(obj)
+    soc.send(data)
+    soc.close()
+    return False

period_2/02-sockets/902/SocketUtil_t.py

@@ -0,0 +1,18 @@
+from TxBlock import *
+from Transaction import *
+from Signature import *
+
+from SocketUtil import *
+
+TCP_PORT = 5050
+BUFFER_SIZE = 1024
+SERVER = 'localhost'
+
+if __name__ == "__main__":
+
+    server = newServerSocket(SERVER)
+    print('A connection to the server is established.')
+    Obj = recvObj(server)
+
+    print("Success! The connection is released.")  # If returns after time, then successful
+    server.close()

period_2/02-sockets/902/Transaction.py

@@ -0,0 +1,88 @@
+from Signature import *
+
+class Tx:
+    inputs = None
+    outputs =None
+    sigs = None
+    reqd = None
+    def __init__(self):
+        self.inputs = []
+        self.outputs = []
+        self.sigs = []
+        self.reqd = []
+
+    def add_input(self, from_addr, amount):
+        self.inputs.append((from_addr, amount))
+
+    def add_output(self, to_addr, amount):
+        self.outputs.append((to_addr, amount))
+
+    def add_reqd(self, addr):
+        self.reqd.append(addr)
+
+    def sign(self, private):
+        message = self.__gather()
+        newsig = sign(message, private)
+        self.sigs.append(newsig)
+               
+    def is_valid(self):
+        total_in = 0
+        total_out = 0
+        message = self.__gather()
+        for addr,amount in self.inputs:
+            found = False
+            for s in self.sigs:
+                if verify(message, s, addr):
+                    found = True
+            if not found:
+                # print ("No good sig found for " + str(message))
+                return False
+            if amount < 0:
+                return False
+            total_in = total_in + amount
+        for addr in self.reqd:
+            found = False
+            for s in self.sigs:
+                if verify(message, s, addr):
+                    found = True
+            if not found:
+                return False
+        for addr,amount in self.outputs:
+            if amount < 0:
+                return False
+            total_out = total_out + amount
+
+        # if total_out > total_in:
+        #     # print("Outputs exceed inputs")
+        #     return False
+        
+        return True
+
+    def __gather(self):
+        data=[]
+        data.append(self.inputs)
+        data.append(self.outputs)
+        data.append(self.reqd)
+        return data
+
+    def __repr__(self):
+
+        repr_str = "INPUTS:\n"
+        for addr, amt in self.inputs:
+            repr_str = repr_str + str(amt) + "from" + str(addr) + "\n"
+
+        repr_str += "OUTPUTS:\n"
+        for addr, amt in self.outputs:
+            repr_str = repr_str + str(amt) + "to" + str(addr) + "\n"
+
+        repr_str += "EXTRA REQUIRED SIGNATURES:\n"     
+        for req_sig in self.reqd:
+            repr_str = repr_str + str(req_sig) + "\n"
+
+        repr_str += "SIGNATURES:\n"     
+        for sig in self.sigs:
+            repr_str = repr_str + str(sig) + "\n"
+
+        repr_str += "END\n"
+        
+        return repr_str

period_2/02-sockets/902/TxBlock.py

@@ -0,0 +1,60 @@
+from BlockChain import CBlock
+from Signature import generate_keys, sign, verify
+from cryptography.hazmat.primitives import hashes
+from cryptography.hazmat.backends import default_backend
+
+import random
+
+reward = 25.0
+leading_zeros = 2
+next_char_limit = 20
+
+class TxBlock(CBlock):
+
+    nonce = "A random nonce"
+
+    def __init__(self, previousBlock):
+        super(TxBlock, self).__init__([], previousBlock)
+
+    def addTx(self, Tx_in):
+        self.data.append(Tx_in)
+
+    def __count_totals(self):
+        total_in = 0
+        total_out = 0
+        for tx in self.data:
+            for addr, amt in tx.inputs:
+                total_in = total_in + amt
+            for addr, amt in tx.outputs:
+                total_out = total_out + amt
+        return total_in, total_out
+
+    def is_valid(self):
+        if not super(TxBlock, self).is_valid():
+            return False
+        for tx in self.data:
+            if not tx.is_valid():
+                return False
+        total_in, total_out = self.__count_totals()
+        if total_out - total_in - reward > 0.000000000001:
+            return False
+        return True
+
+    def good_nonce(self):
+        digest = hashes.Hash(hashes.SHA256(), backend=default_backend())
+        digest.update(bytes(str(self.data), 'utf8'))
+        digest.update(bytes(str(self.previousHash), 'utf8'))
+        digest.update(bytes(str(self.nonce), 'utf8'))
+        this_hash = digest.finalize()
+
+        if this_hash[:leading_zeros] != bytes(''.join(['\x4f' for i in range(leading_zeros)]), 'utf8'):
+            return False
+        return int(this_hash[leading_zeros]) < next_char_limit
+
+    def find_nonce(self):
+        for i in range(1000000):
+            self.nonce = ''.join([
+                chr(random.randint(0, 255)) for i in range(10*leading_zeros)])
+            if self.good_nonce():
+                return self.nonce
+        return None