Initial commit

Client.py

@@ -0,0 +1,52 @@
+import socket
+from cryptography.fernet import Fernet
+import time
+
+user   = "Alice"
+server = "Bob"
+key_AS = b"UFltX3Uf9qIQ6UyIElj3awsXWDHsC2QjZ8GObFMqzmQ="
+
+## COMM. WITH KDC
+client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+port_KDC, port_server = 11111, 22222
+client.connect(("127.0.0.1", port_KDC))
+# Step 1
+client.send(user.encode())
+enc = client.recv(1024)
+print("Sending connection request to Authentication Server...")
+
+# Step 2
+fernet_1 = Fernet(key_AS)
+(key_TGS, enc_2) = fernet_1.decrypt(enc).decode().split()
+print("Ticket received from Authentication Server")
+print(f"Ticket: {key_TGS}")
+# Step 3
+fernet_2 = Fernet(key_TGS)
+nonce = int(time.time())
+enc_1 = fernet_2.encrypt((server + ' ' + str(nonce)).encode())
+enc = enc_1.decode() + ' ' + enc_2
+client.send(enc.encode())
+print(f"Sending Nonce: {nonce} to Ticket Granting Server...")
+# Step 4
+(enc_1, enc_2) = client.recv(1024).decode().split()
+(server_tmp, key_session) = fernet_2.decrypt(enc_1.encode()).decode().split()
+client.close()
+print("Session Key received from Ticket Granting Server")
+print(f"Session Key: {key_session}")
+print()
+
+## COMM. WITH SERVER
+client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+client.connect(("127.0.0.1", port_server))
+# Step 5
+print(f"Sending Nonce: {nonce} and Session Key to Server: {server}...")
+fernet_3 = Fernet(key_session.encode())
+enc_1 = fernet_3.encrypt(str(nonce).encode())
+enc = enc_1.decode() + ' ' + enc_2
+client.send(enc.encode())
+# Step 6
+enc = client.recv(1024)
+nonce_new = fernet_3.decrypt(enc).decode()
+print(f"New Nonce: {nonce_new} received from Server: {server}")
+print(f"Connection Established Successfully")
+client.close()

KDC.py

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+import socket
+from cryptography.fernet import Fernet
+
+key_AS = {}
+key_TGS = {}
+key_AS_TGS      = b"nrpuhqpzDIPzn_QxHIOE4LpZNHi5AP8lRy_wfCTqN4s="
+key_AS["Alice"] = b"UFltX3Uf9qIQ6UyIElj3awsXWDHsC2QjZ8GObFMqzmQ=" 
+key_TGS["Bob"]  = b"BgIFUaxnefMzR1FI_Sv-meLxCV4e5RI6zp-5Y_RlR6s="
+
+kdc = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+kdc.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+port = 11111          
+kdc.bind(("127.0.0.1", port))        
+kdc.listen(5)    
+
+while True:
+    # Step 1
+    c, addr = kdc.accept()  
+    user = c.recv(1024).decode()
+    print(f"Connection request received from Client: {user}, Address: {addr}")
+    # Step 2
+    key_TGS[user] = Fernet.generate_key()
+    fernet_1 = Fernet(key_AS_TGS)
+    inner = fernet_1.encrypt((user + ' ' + key_TGS[user].decode()).encode())
+    fernet_2 = Fernet(key_AS[user])
+    outer = fernet_2.encrypt((key_TGS[user].decode() + ' ' + inner.decode()).encode())
+    c.send(outer)
+    print(f"Sending Ticket: {key_TGS[user]} to Client: {user}...")
+    # Step 3
+    (enc_1, enc_2) = c.recv(1024).decode().split()
+    print("Nonce received")
+    # Step 4
+    key_session = Fernet.generate_key()
+    fernet_3 = Fernet(key_TGS[user])
+    (server, nonce) = fernet_3.decrypt(enc_1.encode()).decode().split()
+    fernet_4 = Fernet(key_TGS[server])
+    (user, key_tmp) = fernet_1.decrypt(enc_2.encode()).decode().split() 
+    enc_1 = fernet_3.encrypt((server + ' ' + key_session.decode()).encode())
+    enc_2 = fernet_4.encrypt((user   + ' ' + key_session.decode()).encode())
+    enc = (enc_1.decode() + ' ' + enc_2.decode()).encode()
+    c.send(enc)
+    print(f"Sending Session Key: {key_session} to Client: {user}...")
+    c.close()
+    break

Server.py

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+import socket
+from cryptography.fernet import Fernet
+
+user   = "Alice"
+server = "Bob"
+key_TGS = b"BgIFUaxnefMzR1FI_Sv-meLxCV4e5RI6zp-5Y_RlR6s="
+
+server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+port = 22222          
+server_socket.bind(("127.0.0.1", port))        
+server_socket.listen(5)    
+
+while True:
+    # Step 5
+    c, addr = server_socket.accept()    
+    (enc_1, enc_2) = c.recv(1024).decode().split()
+    print(f"Connection request received from Client: {user}, Address: {addr}")
+    # Step 6
+    fernet_1 = Fernet(key_TGS)
+    (user_tmp, key_session) = fernet_1.decrypt(enc_2.encode()).split()
+    fernet_2 = Fernet(key_session)
+    nonce = fernet_2.decrypt(enc_1.encode()).decode()
+    nonce_new = str(int(nonce) - 1)
+    enc = fernet_2.encrypt(nonce_new.encode())
+    c.send(enc)
+    print(f"Nonce: {nonce} received from Client: {user_tmp}")
+    print(f"Session Key: {key_session} received from Client: {user_tmp}")
+    print(f"Sending new Nonce: {nonce_new} to Client: {user_tmp}...")
+    c.close()
+    break