diff --git a/alex.keys b/alex.keys
deleted file mode 100644
index 0d5f7d7..0000000
Binary files a/alex.keys and /dev/null differ
diff --git a/block.dat b/block.dat
deleted file mode 100644
index 74ee6ec..0000000
Binary files a/block.dat and /dev/null differ
diff --git a/mike.keys b/mike.keys
deleted file mode 100644
index 61de7bc..0000000
Binary files a/mike.keys and /dev/null differ
diff --git a/period_2/01-sockets/801/client.py b/period_2/01-sockets/801/client.py
new file mode 100644
index 0000000..2788c82
--- /dev/null
+++ b/period_2/01-sockets/801/client.py
@@ -0,0 +1,26 @@
+import socket
+
+HOST = socket.gethostbyname("localhost")
+PORT = 5050
+
+# create a message input
+message = input("Please enter a message: ")
+
+# create and bind socket
+socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+socket.connect((HOST, PORT))
+
+
+
+# send message
+socket.sendall(message.encode())
+
+# socket.recvmsg(1024)
+
+print("Message sent")
+socket.close()
+
+
+
+
+
diff --git a/period_2/01-sockets/801/server.py b/period_2/01-sockets/801/server.py
new file mode 100644
index 0000000..860d4e7
--- /dev/null
+++ b/period_2/01-sockets/801/server.py
@@ -0,0 +1,21 @@
+import socket
+
+HOST = socket.gethostbyname("localhost")
+PORT = 8080
+
+# create and bind socket
+socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+socket.bind((HOST, PORT))
+
+# become a server socket
+socket.listen(2)
+
+# accept connections
+while True:
+    connection, address = socket.accept()
+    print("Connection from", address)
+    data = connection.recv(1024)
+    print("Received: ", data.decode())
+    connection.close()
+    break
+
diff --git a/period_2/01-sockets/802/client.py b/period_2/01-sockets/802/client.py
new file mode 100644
index 0000000..9e16085
--- /dev/null
+++ b/period_2/01-sockets/802/client.py
@@ -0,0 +1,28 @@
+import socket
+
+HOST = socket.gethostbyname("145.137.113.215")
+PORT = 5055
+
+# create a message input
+message = "1001519"
+
+# create and bind socket
+socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+socket.connect((HOST, PORT))
+
+
+
+# send message
+socket.sendall(bytes(message, "utf-8"))
+data = socket.recv(1024)
+
+# socket.recvmsg(1024)
+
+print("Message sent")
+
+socket.close()
+
+
+
+
+
diff --git a/period_2/01-sockets/803/client.py b/period_2/01-sockets/803/client.py
new file mode 100644
index 0000000..ca50e3f
--- /dev/null
+++ b/period_2/01-sockets/803/client.py
@@ -0,0 +1,31 @@
+import socket
+
+HOST = socket.gethostbyname("localhost")
+PORT = 5052
+
+def send(msg):
+
+
+    # create a message input
+    message = msg.encode("utf-8")
+
+    # create and bind socket
+    socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    socket.connect((HOST, PORT))
+
+    # send message
+    socket.send(b'-' * (64 - len(str(len(message)).encode("utf-8"))))
+    socket.send(message)
+
+    socket.recv(1024)
+
+    print("Message sent")
+    socket.close()
+
+message = input("Please enter a message: ")
+
+if message == "":
+    send("!DISCONNECT")
+
+else:
+    send(message)
\ No newline at end of file
diff --git a/period_2/01-sockets/803/server.py b/period_2/01-sockets/803/server.py
new file mode 100644
index 0000000..1de9242
--- /dev/null
+++ b/period_2/01-sockets/803/server.py
@@ -0,0 +1,34 @@
+import socket
+# Get local machine name
+HOST = socket.gethostname("localhost")
+PORT = 5050
+
+def handleClient(clientsocket):
+    while True:
+        # Receive no more than 1024 bytes
+        msg = clientsocket.recv(1024)
+        if not msg:
+            break
+        clientsocket.send(msg)
+    clientsocket.close()
+
+def start():
+    # Create a socket object
+    serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+
+
+    # Bind to the port
+    serversocket.bind((HOST, PORT))
+
+    # Queue up to 5 requests
+    serversocket.listen(5)
+
+    while True:
+        # Establish a connection
+        clientsocket, addr = serversocket.accept()
+
+        print("Got a connection from %s" % str(addr))
+
+        msg = 'Thank you for connecting' + "\r\n"
+        clientsocket.send(msg.encode('ascii'))
+        clientsocket.close()
\ No newline at end of file
diff --git a/period_2/01-sockets/804/client.py b/period_2/01-sockets/804/client.py
new file mode 100644
index 0000000..8ed6636
--- /dev/null
+++ b/period_2/01-sockets/804/client.py
@@ -0,0 +1,30 @@
+import socket
+
+HOST = socket.gethostbyname("localhost")
+PORT = 5053
+ADDR = (HOST, PORT)
+HEADER = 64
+FORMAT = "utf-8"
+
+server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+server.connect(ADDR)
+
+def send(message):
+    message = message.encode(FORMAT)
+    msg_length = len(message)
+    send_length = str(msg_length).encode(FORMAT)
+    send_length += b' ' * (HEADER - len(send_length))
+    server.send(send_length)
+    server.send(message)
+    print(server.recv(2048).decode(FORMAT))
+
+def handleSend():
+    connected = True
+    while connected:
+        message = input("Please enter a message: ")
+        if message == "!DISCONNECT":
+            connected = False
+        else:
+            send(message)
+
+handleSend()
\ No newline at end of file
diff --git a/period_2/01-sockets/804/server.py b/period_2/01-sockets/804/server.py
new file mode 100644
index 0000000..c7c5caf
--- /dev/null
+++ b/period_2/01-sockets/804/server.py
@@ -0,0 +1,44 @@
+import socket
+import threading
+
+HOST = socket.gethostbyname("localhost")
+PORT = 5053
+ADDR = (HOST, PORT)
+HEADER = 64
+FORMAT = "utf-8"
+
+server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+server.bind(ADDR)
+
+def handleClient(conn, addr):
+    client_name = conn.recv(HEADER).decode(FORMAT)
+    print(f"[NEW CONNECTION] {client_name} connected.")
+    connected = True
+    while connected:
+        msg_length = conn.recv(HEADER).decode(FORMAT)
+        if msg_length:
+            msg_length = int(len(msg_length))
+            msg = conn.recv(msg_length).decode(FORMAT)
+            if msg == "!DISCONNECT":
+                connected = False
+            print(f"[{client_name}] {msg}")
+            conn.send("Msg received".encode(FORMAT))
+
+    conn.send("Bye bye".encode(FORMAT))
+    conn.close()
+    print(f"[DISCONNECTED] {client_name} disconnected.")
+    print(f"[ACTIVE CONNECTIONS] {threading.activeCount() - 2}]")
+
+
+
+def start():
+    server.listen()
+    print(f"[LISTENING] Server is listening on {HOST}")
+    while True:
+        conn, addr = server.accept()
+        thread = threading.Thread(target=handleClient, args=(conn, addr))
+        thread.start()
+        print(f"[ACTIVE CONNECTIONS] {threading.activeCount() - 1}")
+
+print("[STARTING] server is starting...")
+start()
\ No newline at end of file
diff --git a/period_2/01-sockets/807_T07_A07_SendReceiveBlock_Local/BlockChain.py b/period_2/01-sockets/807_T07_A07_SendReceiveBlock_Local/BlockChain.py
new file mode 100644
index 0000000..c20e155
--- /dev/null
+++ b/period_2/01-sockets/807_T07_A07_SendReceiveBlock_Local/BlockChain.py
@@ -0,0 +1,25 @@
+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.blockHash = None
+        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
\ No newline at end of file
diff --git a/period_2/01-sockets/807_T07_A07_SendReceiveBlock_Local/Signature.py b/period_2/01-sockets/807_T07_A07_SendReceiveBlock_Local/Signature.py
new file mode 100644
index 0000000..740ee1a
--- /dev/null
+++ b/period_2/01-sockets/807_T07_A07_SendReceiveBlock_Local/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
\ No newline at end of file
diff --git a/period_2/01-sockets/807_T07_A07_SendReceiveBlock_Local/Transaction.py b/period_2/01-sockets/807_T07_A07_SendReceiveBlock_Local/Transaction.py
new file mode 100644
index 0000000..518ac8f
--- /dev/null
+++ b/period_2/01-sockets/807_T07_A07_SendReceiveBlock_Local/Transaction.py
@@ -0,0 +1,100 @@
+from gzip import READ
+from operator import truediv
+from optparse import AmbiguousOptionError
+
+REWARD_VALUE = 25.0
+NORMAL = 0
+REWARD = 1
+
+from Signature import *
+
+class Tx:
+    def __init__(self, type = NORMAL):
+        
+        self.type = type
+        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):
+
+        if self.type == REWARD:
+            if len(self.inputs)!=0 and len(self.outputs)!=1:
+                return False
+            return True
+        
+        else:
+            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
diff --git a/period_2/01-sockets/807_T07_A07_SendReceiveBlock_Local/TxBlock.py b/period_2/01-sockets/807_T07_A07_SendReceiveBlock_Local/TxBlock.py
new file mode 100644
index 0000000..4bb47ed
--- /dev/null
+++ b/period_2/01-sockets/807_T07_A07_SendReceiveBlock_Local/TxBlock.py
@@ -0,0 +1,63 @@
+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_VALUE = 25.0
+leading_zeros = 2
+next_char_limit = 20
+
+class TxBlock (CBlock):
+
+    def __init__(self, previousBlock):
+        self.nonce = "A random nonce"
+        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
+        
+        if self.nonce != "A random nonce":
+            if not self.good_nonce():
+                return False
+        
+        total_in, total_out = self.__count_totals()
+        
+        Tx_Balance = round(total_out - total_in, 10)
+        
+        if  Tx_Balance > REWARD_VALUE:
+            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()
+        return this_hash[:leading_zeros] == b'\x00'*leading_zeros
+
+    def find_nonce(self):
+        for i in range(10000000):
+            self.nonce = i
+            if self.good_nonce():
+                return self.nonce
+        return None
diff --git a/period_2/01-sockets/807_T07_A07_SendReceiveBlock_Local/client.py b/period_2/01-sockets/807_T07_A07_SendReceiveBlock_Local/client.py
new file mode 100644
index 0000000..5f3b118
--- /dev/null
+++ b/period_2/01-sockets/807_T07_A07_SendReceiveBlock_Local/client.py
@@ -0,0 +1,11 @@
+import pickle
+import socket
+
+PORT = 5005
+
+def sendObj(ip_address, obj):
+    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    sock.connect((ip_address, PORT))
+    sock.send(pickle.dumps(obj))
+    sock.close()
+    return False
\ No newline at end of file
diff --git a/period_2/01-sockets/807_T07_A07_SendReceiveBlock_Local/client_t.py b/period_2/01-sockets/807_T07_A07_SendReceiveBlock_Local/client_t.py
new file mode 100644
index 0000000..76fad33
--- /dev/null
+++ b/period_2/01-sockets/807_T07_A07_SendReceiveBlock_Local/client_t.py
@@ -0,0 +1,36 @@
+from TxBlock import *
+from Transaction import *
+from Signature import *
+
+from client 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)
+
+    sendObj(SERVER, B1)
+
+    sendObj(SERVER, Tx2)
diff --git a/period_2/01-sockets/807_T07_A07_SendReceiveBlock_Local/server.py b/period_2/01-sockets/807_T07_A07_SendReceiveBlock_Local/server.py
new file mode 100644
index 0000000..1e9cdf1
--- /dev/null
+++ b/period_2/01-sockets/807_T07_A07_SendReceiveBlock_Local/server.py
@@ -0,0 +1,21 @@
+import socket
+import pickle
+import TxBlock
+
+PORT = 5050
+
+def newConnection(ip_address):
+    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    sock.bind((ip_address, PORT))
+    sock.listen(2)
+    return sock
+
+def recvObj(socket):
+    new_sock, address = socket.accept()
+    data = new_sock.recv(1024)
+    print("Received: ", data)
+    data = pickle.loads(data)
+    new_sock.close()
+    return data
+
+
diff --git a/period_2/01-sockets/807_T07_A07_SendReceiveBlock_Local/server_t.py b/period_2/01-sockets/807_T07_A07_SendReceiveBlock_Local/server_t.py
new file mode 100644
index 0000000..c3d077b
--- /dev/null
+++ b/period_2/01-sockets/807_T07_A07_SendReceiveBlock_Local/server_t.py
@@ -0,0 +1,50 @@
+import TxBlock
+import socket
+import pickle
+
+from server import *
+
+SERVER = 'localhost'
+TCP_PORT = 5050
+# BUFFER_SIZE = 1024
+
+if __name__ == "__main__":
+
+    server = newConnection(SERVER)
+
+    newB = recvObj(server)
+    # print(newB.data[0])
+    # print(newB.data[1])
+
+    if (newB.is_valid()):
+        print("Success! Transaction is valid.")
+    else:
+        print("Error! Transaction invalid.")
+
+    if newB.data[0].inputs[0][1] == 2.3:
+        print("Success! Input value matches.")
+    else:
+        print("Error! Wrong input value for block 1, transaction 1.")
+
+    if newB.data[0].outputs[1][1] == 1.1:
+        print("Success! Output value matches.")
+    else:
+        print("Error! Wrong output value for block 1, transaction 1.")
+
+    if newB.data[1].inputs[0][1] == 2.3:
+        print("Success! Input value matches.")
+    else:
+        print("Error! Wrong input value for block 1, transaction 1.")
+
+    if newB.data[1].inputs[1][1] == 1.0:
+        print("Success! Input value matches.")
+    else:
+        print("Error! Wrong input value for block 1, transaction 1.")
+
+    if newB.data[1].outputs[0][1] == 3.1:
+        print("Success! Output value matches.")
+    else:
+        print("Error! Wrong output value for block 1, transaction 1.")
+
+    newTx = recvObj(server)
+    # print(newTx)
diff --git a/period_2/01-sockets/808_T08_A08_SendReceiveBlock_P2P/client_t.py b/period_2/01-sockets/808_T08_A08_SendReceiveBlock_P2P/client_t.py
new file mode 100644
index 0000000..c13fc49
--- /dev/null
+++ b/period_2/01-sockets/808_T08_A08_SendReceiveBlock_P2P/client_t.py
@@ -0,0 +1,36 @@
+from TxBlock import *
+from Transaction import *
+from Signature import *
+
+from client import *
+
+SERVER = 'localhost'
+TCP_PORT = 5005
+
+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.TxBlock(None)
+    B1.addTx(Tx1)
+    B1.addTx(Tx2)
+
+    sendObj(SERVER, B1)
+
+    sendObj(SERVER, Tx2)
diff --git a/period_2/01-sockets/808_T08_A08_SendReceiveBlock_P2P/server_t.py b/period_2/01-sockets/808_T08_A08_SendReceiveBlock_P2P/server_t.py
new file mode 100644
index 0000000..12ad431
--- /dev/null
+++ b/period_2/01-sockets/808_T08_A08_SendReceiveBlock_P2P/server_t.py
@@ -0,0 +1,57 @@
+import TxBlock
+import socket
+import pickle
+
+from server import *
+
+
+local_hostname = socket.gethostname()
+# local_ip = socket.gethostbyname(local_hostname)
+local_ip = '192.168.1.103'
+
+
+TCP_PORT = 5005
+BUFFER_SIZE = 1024
+
+if __name__ == "__main__":
+
+    server = newConnection(local_ip)
+    print(f"[LISTENING] Server is listening on {local_ip}")
+
+
+    newB = recvObj(server)
+    # print(newB.data[0])
+    # print(newB.data[1])
+
+    if (newB.is_valid()):
+        print("Success! Transaction is valid.")
+    else:
+        print("Error! Transaction invalid.")
+
+    if newB.data[0].inputs[0][1] == 2.3:
+        print("Success! Input value matches.")
+    else:
+        print("Error! Wrong input value for block 1, transaction 1.")
+
+    if newB.data[0].outputs[1][1] == 1.1:
+        print("Success! Output value matches.")
+    else:
+        print("Error! Wrong output value for block 1, transaction 1.")
+
+    if newB.data[1].inputs[0][1] == 2.3:
+        print("Success! Input value matches.")
+    else:
+        print("Error! Wrong input value for block 1, transaction 1.")
+
+    if newB.data[1].inputs[1][1] == 1.0:
+        print("Success! Input value matches.")
+    else:
+        print("Error! Wrong input value for block 1, transaction 1.")
+
+    if newB.data[1].outputs[0][1] == 3.1:
+        print("Success! Output value matches.")
+    else:
+        print("Error! Wrong output value for block 1, transaction 1.")
+
+    newTx = recvObj(server)
+    # print(newTx)
diff --git a/period_2/02-sockets/901_T01_A01_CS_MultiCon_Sync_NonB_Recv.zip/client.py b/period_2/02-sockets/901_T01_A01_CS_MultiCon_Sync_NonB_Recv.zip/client.py
new file mode 100644
index 0000000..ff3e7dd
--- /dev/null
+++ b/period_2/02-sockets/901_T01_A01_CS_MultiCon_Sync_NonB_Recv.zip/client.py
@@ -0,0 +1,52 @@
+import socket
+from threading import Timer
+
+HEADER = 64
+PORT = 5053
+FORMAT = 'utf-8'
+DISCONNECT_MESSAGE = "!DISCONNECT"
+HOST_IP = 'localhost'
+
+ADDR = (HOST_IP, PORT)
+
+client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+client.connect(ADDR)
+client_name = input('please enter your name: ')
+client.send(client_name.encode(FORMAT))
+print(client.recv(2048).decode(FORMAT))
+
+def send(msg):
+    message = msg.encode(FORMAT)
+    msg_length = len(message)
+    send_length = str(msg_length).encode(FORMAT)
+    send_length += b' ' * (HEADER - len(send_length))
+    client.send(send_length)
+    client.send(message)
+    print(client.recv(2048).decode(FORMAT))
+
+def stop_the_client():
+    global cont_flag
+    mes = DISCONNECT_MESSAGE
+    send(mes)
+    cont_flag = False
+
+cont_flag = True
+while cont_flag:
+    timeout = 20
+    timeout_thread = Timer(timeout, send, args=(DISCONNECT_MESSAGE,))
+    timeout_thread.start()
+
+    if not cont_flag:
+        print("the connection is closed by the server")
+        break
+    print('--------------------------')
+    print('You can send a message to server')
+    print('to stop connection, press enter on a blank message')
+    mes = input('Your message: ')
+    if mes:
+        send(mes)
+    else:
+        send(DISCONNECT_MESSAGE)
+        cont_flag = False
+
+    timeout_thread.cancel()
diff --git a/period_2/02-sockets/901_T01_A01_CS_MultiCon_Sync_NonB_Recv.zip/server.py b/period_2/02-sockets/901_T01_A01_CS_MultiCon_Sync_NonB_Recv.zip/server.py
new file mode 100644
index 0000000..b199056
--- /dev/null
+++ b/period_2/02-sockets/901_T01_A01_CS_MultiCon_Sync_NonB_Recv.zip/server.py
@@ -0,0 +1,65 @@
+import socket 
+import threading
+import select
+
+HEADER = 64
+PORT = 5053
+local_ip = socket.gethostbyname('localhost')
+ADDR = (local_ip, PORT)
+FORMAT = 'utf-8'
+DISCONNECT_MESSAGE = "!DISCONNECT"
+
+server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+server.bind(ADDR)
+
+def handle_client(conn, addr):
+    client_name = conn.recv(2048).decode(FORMAT)
+
+    print(f"\n[NEW CONNECTION] {client_name}@{addr} is connected.")
+    connection_message = f"...\nHi {client_name}! \nYou are successfully connected to the server {ADDR}"
+    conn.send(connection_message.encode(FORMAT))
+    connected = True
+    while connected:
+        ready_to_read, ready_to_write, in_error = select.select([conn], [], [conn], 20)
+        print(f"ready_to_read: {ready_to_read}")
+        if len(ready_to_read):
+            print(f"ready_to_read: {ready_to_read}")
+            msg_length = conn.recv(HEADER).decode(FORMAT)
+            print(f"msg_length: {msg_length}")
+            if msg_length:
+
+                msg_length = int(msg_length)
+                msg = conn.recv(msg_length).decode(FORMAT)
+                if msg == DISCONNECT_MESSAGE:
+                    connected = False
+
+            print(f"[{client_name}@{addr}]>> {msg}")
+            return_message = f'Server received your message: "{msg}"'
+            conn.send(return_message.encode(FORMAT))
+        else:
+            connected = False
+            return_message = f"\nTimeout! {client_name} is disconnected from the server {ADDR}"
+            conn.send(return_message.encode(FORMAT))
+
+    bye_message = f"\nBye {client_name}!"
+    conn.send(bye_message.encode(FORMAT))
+    conn.close()
+    print(f"[ACTIVE CONNECTIONS] {threading.active_count() - 2}")
+    
+    # bye_message = f"\nBye {client_name}!"
+    # conn.send(bye_message.encode(FORMAT))
+    conn.close()
+    print(f"[ACTIVE CONNECTIONS] {threading.active_count() - 2}")    
+
+def start():
+    server.listen()
+    print(f"[LISTENING] Server is listening on {local_ip}")
+    while True:
+        conn, addr = server.accept()
+        thread = threading.Thread(target=handle_client, args=(conn, addr))
+        thread.start()
+        print(f"[ACTIVE CONNECTIONS] {threading.active_count() - 1}")
+
+
+print("[STARTING] server is starting...")
+start()
\ No newline at end of file
diff --git a/period_2/02-sockets/902/BlockChain.py b/period_2/02-sockets/902/BlockChain.py
new file mode 100644
index 0000000..d3879c9
--- /dev/null
+++ b/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
\ No newline at end of file
diff --git a/period_2/02-sockets/902/Client_test.py b/period_2/02-sockets/902/Client_test.py
new file mode 100644
index 0000000..1f0c60d
--- /dev/null
+++ b/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()
diff --git a/period_2/02-sockets/902/Signature.py b/period_2/02-sockets/902/Signature.py
new file mode 100644
index 0000000..740ee1a
--- /dev/null
+++ b/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
\ No newline at end of file
diff --git a/period_2/02-sockets/902/SocketUtil.py b/period_2/02-sockets/902/SocketUtil.py
new file mode 100644
index 0000000..320bd26
--- /dev/null
+++ b/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
diff --git a/period_2/02-sockets/902/SocketUtil_t.py b/period_2/02-sockets/902/SocketUtil_t.py
new file mode 100644
index 0000000..b922221
--- /dev/null
+++ b/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()
\ No newline at end of file
diff --git a/period_2/02-sockets/902/Transaction.py b/period_2/02-sockets/902/Transaction.py
new file mode 100644
index 0000000..7f2fe0e
--- /dev/null
+++ b/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
diff --git a/period_2/02-sockets/902/TxBlock.py b/period_2/02-sockets/902/TxBlock.py
new file mode 100644
index 0000000..879fece
--- /dev/null
+++ b/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
diff --git a/period_2/02-sockets/903/BlockChain.py b/period_2/02-sockets/903/BlockChain.py
new file mode 100644
index 0000000..d3879c9
--- /dev/null
+++ b/period_2/02-sockets/903/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
\ No newline at end of file
diff --git a/period_2/02-sockets/903/Miner_a.py b/period_2/02-sockets/903/Miner_a.py
new file mode 100644
index 0000000..e36c03f
--- /dev/null
+++ b/period_2/02-sockets/903/Miner_a.py
@@ -0,0 +1,86 @@
+
+from SocketUtil import *
+import TxBlock as Tx
+# import Tx
+
+SERVER = 'localhost'
+
+wallet_list = [SERVER]
+tx_list = []
+
+def minerServer(my_ip, wallet_list):
+    miner_server_socket = newServerSocket(my_ip, 5050)
+
+    # receive 2 transactions
+    for i in range(10):
+        newTx = recvObj(miner_server_socket)
+        if isinstance(newTx, Tx):
+            tx_list.append(newTx)
+            print("Received Tx")
+        if len(tx_list) == 2:
+            break
+
+    if len(tx_list) < 2:
+        print("Error! Not enough transactions received.")
+        return
+    
+    # collect into block
+    newBlock = TxBlock(None)
+    for tx in tx_list:
+        newBlock.addTx(tx)
+
+    # find nonce
+    newBlock.find_nonce()
+    if newBlock.good_nonce():
+        print("Success! Nonce is valid.")
+    else:
+        print("Error! Nonce is invalid.")
+        return
+    
+    # send that block to each in wallet_list
+    for wallet in wallet_list:
+        sendObj(wallet, newBlock)
+
+    return
+
+
+    # Open Server Connection
+    # Rec'v 2 transactions
+    # Collect into block
+    # Find nonce
+    # Send that block to each in walle_list
+    # return
+
+
+def minerServer(my_ip, wallet_list):
+    # open server connection for the miner
+    server_socket = newServerSocket(my_ip, 5050)
+    print('Server is ready to receive data ...')
+
+    # receive 2 transactions
+    data = recvObj(server_socket)
+    print('Server is receiving data ...')
+    if data:
+        print('Data: ', type(data), '\n')
+    else:
+        print('No object received')
+
+    # collect into block
+    if data:
+        block = TxBlock(None)
+        block.addTx(data)
+    data = recvObj(server_socket)
+    if data:
+        block.addTx(data)
+    server_socket.close()
+
+    # find nonce
+    block.find_nonce()
+    # send that block to each in wallet_list
+    for wallet in wallet_list:
+        sendObj(wallet, block)
+
+    return
+
+
+minerServer('localhost', wallet_list)
diff --git a/period_2/02-sockets/903/Signature.py b/period_2/02-sockets/903/Signature.py
new file mode 100644
index 0000000..740ee1a
--- /dev/null
+++ b/period_2/02-sockets/903/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
\ No newline at end of file
diff --git a/period_2/02-sockets/903/SocketUtil.py b/period_2/02-sockets/903/SocketUtil.py
new file mode 100644
index 0000000..827a8fd
--- /dev/null
+++ b/period_2/02-sockets/903/SocketUtil.py
@@ -0,0 +1,41 @@
+import socket
+import pickle
+import select
+
+BUFFER_SIZE = 1024
+
+def newServerSocket(ip_addr, port):
+    server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    server_socket.bind((ip_addr, port))
+    server_socket.listen()
+    return server_socket
+
+
+def recvObj(socket):
+    inputs, outputs, errs = select.select([socket], [], [socket], 6)
+    if socket in inputs:
+        connected_socket, addr = socket.accept()
+        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, blk, port):
+    soc = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    soc.connect((ip_addr, port))
+    data = pickle.dumps(blk)
+    soc.send(data)
+    soc.close()
+    return False
+
+
+
+
+# changes on newServerConnection 
+# We modified it to accept port number as a parameter, such that when 
+# we make a server we can specify on which port bind it
\ No newline at end of file
diff --git a/period_2/02-sockets/903/Transaction.py b/period_2/02-sockets/903/Transaction.py
new file mode 100644
index 0000000..7f2fe0e
--- /dev/null
+++ b/period_2/02-sockets/903/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
diff --git a/period_2/02-sockets/903/TxBlock.py b/period_2/02-sockets/903/TxBlock.py
new file mode 100644
index 0000000..0ed9e17
--- /dev/null
+++ b/period_2/02-sockets/903/TxBlock.py
@@ -0,0 +1,64 @@
+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
+
+
+
+# count_total() needs to be public to be used in Miner
\ No newline at end of file
diff --git a/period_2/02-sockets/903/Wallet_t.py b/period_2/02-sockets/903/Wallet_t.py
new file mode 100644
index 0000000..13b7bae
--- /dev/null
+++ b/period_2/02-sockets/903/Wallet_t.py
@@ -0,0 +1,69 @@
+from SocketUtil import *
+from Transaction import *
+from Signature import *
+
+M_SERVER_IP = 'localhost'
+M_SERVER_PORT = 5005
+
+W_SERVER_IP = 'localhost'
+W_SERVER_PORT = 5006
+
+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, 4.0)
+Tx1.add_input(mike_pbc, 1.0)
+Tx1.add_output(rose_pbc, 4.8)
+Tx1.sign(alex_prv)
+Tx1.sign(mike_prv)
+
+Tx2 = Tx()
+Tx2.add_input(rose_pbc, 4.0)
+Tx2.add_output(mike_pbc, 4.0)
+Tx2.add_reqd(alex_pbc)
+Tx2.sign(rose_prv)
+Tx2.sign(alex_prv)
+
+print(Tx1.is_valid())
+print(Tx2.is_valid())
+
+try:
+    sendObj(M_SERVER_IP, Tx1, M_SERVER_PORT)
+    print("Sent Tx1")
+    sendObj(M_SERVER_IP, Tx2, M_SERVER_PORT)
+    print("Sent Tx2")
+
+except:
+    print("Error! Connection unsuccessful.")
+
+wallet_server_socket = newServerSocket(W_SERVER_IP, W_SERVER_PORT)
+
+for i in range(10):
+    newBlock = recvObj(wallet_server_socket)
+    if newBlock:
+        break
+wallet_server_socket.close()
+
+if newBlock.is_valid():
+    print("Success! Block is valid.")
+
+if newBlock.good_nonce():
+    print("Success! Nonce is valid.")
+
+tx1_found = tx2_found = False
+for tx in newBlock.data:
+    try:
+        if tx.inputs[0][0] == alex_pbc and tx.inputs[0][1] == 4.0:
+            print("Tx1 is present.")
+            tx1_found = True
+    except:
+        pass
+    try:
+        if tx.inputs[0][0] == rose_pbc and tx.inputs[0][1] == 4.0:
+            print("Tx2 is present.")
+            tx2_found = True
+    except:
+        pass
\ No newline at end of file
diff --git a/rose.keys b/rose.keys
deleted file mode 100644
index 17548a1..0000000
Binary files a/rose.keys and /dev/null differ