diff --git a/trabalho4/AES.py b/trabalho4/AES.py
new file mode 100644
index 0000000..b32bb44
--- /dev/null
+++ b/trabalho4/AES.py
@@ -0,0 +1,21 @@
+from Crypto.Cipher import AES
+
+class AESCipher(object):
+    def __init__(self, key):
+        self.key = key
+        self.nonce = b'\xeb\x06\xfa\xa5C{3\x9d\x9dj\x18\xa2V\xe5\xcb\xc2'
+
+    def encrypt(self, raw):
+        cipher = AES.new(self.key, AES.MODE_EAX, nonce=self.nonce)
+        ciphertext, _ = cipher.encrypt_and_digest(raw.encode())
+        return ciphertext
+
+    def decrypt(self, enc):
+        if type(enc) == str:
+            enc = eval(enc)
+
+        cipher = AES.new(self.key, AES.MODE_EAX, nonce=self.nonce)
+
+        plaintext = cipher.decrypt(enc)
+        print('plaintext', type(plaintext), plaintext)
+        return plaintext.decode()
diff --git a/trabalho4/as.py b/trabalho4/as.py
new file mode 100644
index 0000000..1157e7d
--- /dev/null
+++ b/trabalho4/as.py
@@ -0,0 +1,104 @@
+from common import *
+from hashlib import sha256
+import socket
+from AES import AESCipher
+import os
+
+HOST = "127.0.0.1"
+PORT = AS_PORT
+
+def process_message(message):
+    print(message)
+    message = message.split("||")
+
+    if message[0] == "register":
+        body = message[1].split(",")
+        username = body[0]
+        password = body[1]
+        password = sha256(password.encode()).hexdigest()
+        key = message[3]
+        return register_user(username, password, key)
+    elif message[0] == "login":
+        body = message[1].split(",")
+        username = body[0]
+        password = body[1]
+        password = sha256(password.encode()).hexdigest()
+        return login(username, password)
+    elif message[0] == "request":
+        """
+        M1 = [ID_C + {ID_S + T_R + N1}Kc]
+
+        T_c_tgs = {ID_C + T_R + K_c_tgs}K_tgs
+        M2 = [{K_c_tgs + N_1}Kc + T_c_tgs]
+        """
+        body = message[1].split(",")
+
+        ID_C = body[0]
+        key = get_key(ID_C)
+        AES = AESCipher(key)
+        K_tgs = C_K_tgs
+        M2_AES = AESCipher(K_tgs)
+
+        inner_message = AES.decrypt(body[1])
+        inner_message = inner_message.split(",")
+        T_R = inner_message[1]
+        N1 = inner_message[2]
+
+        K_c_tgs = os.urandom(16)
+        T_c_tgs = f"{ID_C},{T_R},{K_c_tgs}"
+        T_c_tgs = M2_AES.encrypt(T_c_tgs)
+
+        M2 = f"{K_c_tgs},{N1}"
+        M2 = AES.encrypt(M2)
+        M2 = f"{M2},{T_c_tgs}"
+        print('sending m2', M2)
+        return M2
+    else:
+        print("Invalid message")
+
+def register_user(username, password, key):
+    with open("users.data", "a") as f:
+        f.write(f"{username},{password},{key.encode()}\n")
+    return f"success,{key}"
+
+def login(username, password):
+    with open("users.data", "r", newline='\n') as f:
+        for line in f:
+            line = line.strip()
+            line = line.replace("\n", "")
+            user, pw, key = line.split(",")
+            if user == username and pw == password:
+                key = eval(key)
+                print(f"Login succeeded!")
+                return f"success,{key}"
+        print("Login failed!")
+        return "failure"
+
+def get_key(username):
+    return C_User_Key
+
+    with open("users.data", "r", newline='\n') as f:
+        for line in f:
+            line = line.strip()
+            line = line.replace("\n", "")
+            user, _, key = line.split(",")
+            if user == username:
+                return eval(key)
+
+def main():
+    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
+        s.bind((HOST, PORT))
+        s.listen()
+        while True:
+            conn, addr = s.accept()
+            with conn:
+                print(f"Connected by {addr}")
+                data = conn.recv(4096)
+                data = data.decode()
+
+                response = process_message(data)
+
+                conn.sendall(response.encode())
+
+if __name__ == "__main__":
+    main()
\ No newline at end of file
diff --git a/trabalho4/client.py b/trabalho4/client.py
new file mode 100644
index 0000000..0548926
--- /dev/null
+++ b/trabalho4/client.py
@@ -0,0 +1,183 @@
+from common import *
+import os
+import socket
+from AES import AESCipher
+from random import randint
+
+HOST = "127.0.0.1"
+CLIENT_ID = None
+KEY = None
+
+def register_user(username, password):
+    global CLIENT_ID, KEY
+    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
+        s.connect((HOST, AS_PORT))
+        key = os.urandom(32)
+        message = f"register||{username},{password},{key}"
+        s.sendall(message.encode())
+        data = s.recv(4096)
+
+        data = data.decode()
+        if data == "success":
+            print("Login succeeded!")
+            CLIENT_ID = username
+            KEY = key
+
+def login(username, password):
+    global CLIENT_ID, KEY
+    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
+        s.connect((HOST, AS_PORT))
+        message = f"login||{username},{password}"
+        s.sendall(message.encode())
+        data = s.recv(4096)
+
+        data = data.decode()
+        data = data.split(",")
+        if data[0] == "success":
+            print(f"Login succeeded!")
+            CLIENT_ID = username
+            KEY = data[1]
+
+def print_something():
+    global CLIENT_ID, KEY
+
+    if CLIENT_ID is None:
+        print("You must register or login first!")
+        return
+
+    AES = AESCipher(C_User_Key)
+
+    ID_C = CLIENT_ID
+    ID_S = "PRINTER"
+    T_R = int(input("Enter the ticket lifetime (minutes): "))
+    T_R = T_R * 60
+    N1 = randint(0, 1000000)
+
+    M2 = None
+    M4 = None
+    M6 = None
+
+    M1_inner = f"{ID_S},{T_R},{N1}"
+    M1_inner = AES.encrypt(M1_inner)
+    M1 = f"{ID_C},{M1_inner}"
+    message = f"request||{M1}"
+    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
+        s.connect((HOST, AS_PORT))
+        print('sending m1', message)
+        s.sendall(message.encode())
+
+        data = s.recv(4096)
+        data = data.decode()
+        print('received m2', data)
+        M2 = data
+
+    '''
+    M2 = [{K_c_tgs + N_1}Kc + T_c_tgs]
+    M3 = [{ID_C + ID_S + T_R + N2}K_c_tgs + T_c_tgs]
+    '''
+    M2 = M2.split(",")
+    M2_inner = AES.decrypt(M2[0])
+    M2_inner = M2_inner.split(",")
+
+    K_c_tgs = eval(M2_inner[0])
+    N1 = M2_inner[1]
+    T_c_tgs = M2[1]
+
+    M2_AES = AESCipher(K_c_tgs)
+    N2 = randint(0, 1000000)
+
+    M3_inner = f"{ID_C},{ID_S},{T_R},{N2}"
+    M3_inner = M2_AES.encrypt(M3_inner)
+    M3 = f"{M3_inner},{T_c_tgs}"
+    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
+        s.connect((HOST, TGS_PORT))
+        message = f"request||{M3}"
+        print('sending m3', message)
+        s.sendall(message.encode())
+
+        data = s.recv(4096)
+        data = data.decode()
+        print('received m4', data)
+        M4 = data
+
+    '''
+        M4 = [{K_c_s + T_A + N2}K_c_tgs + T_c_s]
+            T_c_s = {ID_C + T_A + K_c_s}K_s
+        M5 = [{ID_C + T_A + S_R + N3}K_c_s + T_c_s]
+    '''
+    M4 = M4.split(",")
+    M4_AES = AESCipher(K_c_tgs)
+    M4_inner = M4_AES.decrypt(M4[0])
+    M4_inner = M4_inner.split(",")
+    print('M4_inner', M4_inner)
+
+    K_c_s = eval(M4_inner[0])
+    T_A = M4_inner[1]
+    N2 = M4_inner[2]
+
+    T_c_s = M4[1]
+
+    M5_AES = AESCipher(K_c_s)
+    N3 = randint(0, 1000000)
+
+    M5_inner = f"{ID_C},{T_A},{ID_S},{N3}"
+    M5_inner = M5_AES.encrypt(M5_inner)
+    M5 = f"{M5_inner},{T_c_s}"
+
+    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
+        s.connect((HOST, SERVICE_PORT))
+        message = f"request||{M5}"
+        print('sending m5', message)
+        s.sendall(message.encode())
+
+        data = s.recv(4096)
+        data = data.decode()
+        print('received m6', data)
+        M6 = data
+
+    '''
+    M6 = [{Resposta, N3}K_c_s]
+    '''
+    M6 = M6.split(",")
+    M6_AES = AESCipher(K_c_s)
+    M6_inner = M6_AES.decrypt(M6[0])
+    M6_inner = M6_inner.split(",")
+    resposta = M6_inner[0]
+    N3 = M6_inner[1]
+
+    print(f"Resposta: [{resposta}]")
+
+    print("Finished!!!")
+
+
+def main():
+    global CLIENT_ID
+    while True:
+        # os.system("clear")
+
+        print(f"Hello world! Logged as [{CLIENT_ID}]")
+        print("1. Register")
+        print("2. Login")
+        if CLIENT_ID is not None:
+            print("3. Print something")
+        print("0. Exit")
+
+        choice = input("Enter your choice: ")
+
+        if choice == "1":
+            username = input("Enter your username: ")
+            password = input("Enter your password: ")
+            register_user(username, password)
+        elif choice == "2":
+            username = input("Enter your username: ")
+            password = input("Enter your password: ")
+            login(username, password)
+        elif choice == "3":
+            print_something()
+        elif choice == "0":
+            break
+        else:
+            print("Invalid choice")
+
+if __name__ == "__main__":
+    main()
diff --git a/trabalho4/common.py b/trabalho4/common.py
new file mode 100644
index 0000000..2760af6
--- /dev/null
+++ b/trabalho4/common.py
@@ -0,0 +1,7 @@
+AS_PORT = 65431
+TGS_PORT = 65433
+SERVICE_PORT = 65434
+
+C_User_Key = b'\xb0O\x12M\xfe\x99\xc0\xff\xa9B\x12e\xdf\x89\xec\x06\x8fhXy\x95\xc8\xdf\x80\x03F\xd72\x11\xb6\xdb\x06'
+C_K_tgs = b'\xb0O\x12M\xfe\x99\xc0\xff\xa9B\x12e\xdf\x89\xec\x06\x8fhXy\x95\xc8\xdf\x80\x03F\xd72\x11\xb6\xdb\x06'
+C_K_s = b'\xb0O\x12M\xfe\x99\xc0\xff\xa9B\x12e\xdf\x89\xec\x06\x8fhXy\x95\xc8\xdf\x80\x03F\xd72\x11\xb6\xdb\x06'
\ No newline at end of file
diff --git a/trabalho4/service.py b/trabalho4/service.py
new file mode 100644
index 0000000..fca2c1e
--- /dev/null
+++ b/trabalho4/service.py
@@ -0,0 +1,67 @@
+import socket
+from common import *
+import socket
+from AES import AESCipher
+import os
+from random import randint
+
+HOST = "127.0.0.1"
+PORT = SERVICE_PORT
+
+def process_message(message):
+    print(message)
+    message = message.split("||")
+
+    if message[0] == "request":
+        """
+        T_c_s = {ID_C + T_A + K_c_s}K_s
+
+        M5 = [{ID_C + T_A + S_R + N3}K_c_s + T_c_s]
+        M6 = [{Resposta, N3}K_c_s]
+        """
+        body = message[1].split(",")
+        K_s = C_K_s
+        T_c_s_AES = AESCipher(K_s)
+
+        M5_inner = body[0]
+        T_c_s = body[1]
+
+        T_c_s = T_c_s_AES.decrypt(T_c_s)
+        T_c_s = T_c_s.split(",")
+        ID_C = T_c_s[0]
+        T_A = T_c_s[1]
+        K_c_s = T_c_s[2]
+
+        M5_inner_AES = AESCipher(K_c_s)
+        M5_inner = M5_inner_AES.decrypt(M5_inner)
+        M5_inner = M5_inner.split(",")
+        ID_S = M5_inner[2]
+        N3 = M5_inner[3]
+
+        # generate M6
+
+        M6_inner = f"{randint(0, 100)},{N3}"
+        M6_inner_AES = AESCipher(K_c_s)
+        M6_inner = M6_inner_AES.encrypt(M6_inner)
+
+        M6 = f"{M6_inner}"
+        return M6
+
+def main():
+    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
+        s.bind((HOST, PORT))
+        s.listen()
+        while True:
+            conn, addr = s.accept()
+            with conn:
+                print(f"Connected by {addr}")
+                all_data = ""
+                data = conn.recv(4096)
+                all_data += data.decode()
+
+                response = process_message(all_data)
+
+                conn.sendall(response.encode())
+
+if __name__ == "__main__":
+    main()
diff --git a/trabalho4/tgs.py b/trabalho4/tgs.py
new file mode 100644
index 0000000..efad7ae
--- /dev/null
+++ b/trabalho4/tgs.py
@@ -0,0 +1,77 @@
+import socket
+from common import *
+import socket
+from AES import AESCipher
+import os
+
+HOST = "127.0.0.1"
+PORT = TGS_PORT
+
+def process_message(message):
+    print(message)
+    message = message.split("||")
+
+    if message[0] == "request":
+        """
+            T_c_tgs = {ID_C + T_R + K_c_tgs}K_tgs
+
+        M3 = [{ID_C + ID_S + T_R + N2}K_c_tgs + T_c_tgs]
+        M4 = [{K_c_s + T_A + N2}K_c_tgs + T_c_s]
+            T_c_s = {ID_C + T_A + K_c_s}K_s
+        """
+        body = message[1].split(",")
+        K_tgs = C_K_tgs
+
+        M3 = body[0]
+        M3 = M3.split(",")
+        M3_inner = M3[0]
+        T_c_tgs = body[1]
+        print('T_c_tgs', type(T_c_tgs), T_c_tgs)
+
+        M3_AES = AESCipher(K_tgs)
+        T_c_tgs = M3_AES.decrypt(T_c_tgs)
+        T_c_tgs = T_c_tgs.split(",")
+        ID_C = T_c_tgs[0]
+        T_R = int(T_c_tgs[1])
+        K_c_tgs = eval(T_c_tgs[2])
+
+        M3_inner_AES = AESCipher(K_c_tgs)
+        M3_inner = M3_inner_AES.decrypt(M3_inner)
+        M3_inner = M3_inner.split(",")
+        ID_S = M3_inner[1]
+        N2 = M3_inner[3]
+
+        # generate M4
+        K_c_s = os.urandom(16)
+        T_A = 600 if T_R > 600 else T_R
+        T_c_s = f"{ID_C},{T_A},{K_c_s}"
+
+        K_s = C_K_s
+        T_c_s_AES = AESCipher(K_s)
+        T_c_s = T_c_s_AES.encrypt(T_c_s)
+
+        M4_inner = f"{K_c_s},{T_A},{N2}"
+        M4_inner_AES = AESCipher(K_c_tgs)
+        M4_inner = M4_inner_AES.encrypt(M4_inner)
+
+        M4 = f"{M4_inner},{T_c_s}"
+        return M4
+
+def main():
+    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
+        s.bind((HOST, PORT))
+        s.listen()
+        while True:
+            conn, addr = s.accept()
+            with conn:
+                print(f"Connected by {addr}")
+                all_data = ""
+                data = conn.recv(4096)
+                all_data += data.decode()
+
+                response = process_message(all_data)
+
+                conn.sendall(response.encode())
+
+if __name__ == "__main__":
+    main()
diff --git a/trabalho4/users.data b/trabalho4/users.data
new file mode 100644
index 0000000..5fc7f15
--- /dev/null
+++ b/trabalho4/users.data
@@ -0,0 +1 @@
+fake,a665a45920422f9d417e4867efdc4fb8a04a1f3fff1fa07e998e86f7f7a27ae3,b"b'\\x9cs\\xb9\\x9f*\\xd4\\xa8@!.`\\xb1\\xa5y\\x84\\xfcv\\xdd\\x15X\\x0f`\\xfd\\xb1I\\xbf\\xb4\\xc9\\xaa\\xa2{\\x7f'"