diff --git a/README.md b/README.md
index ffec351..c81dc35 100644
--- a/README.md
+++ b/README.md
@@ -10,3 +10,4 @@ Industrial Security Scripts
 * Schneider-Scanner.py: Simple Broadcast scanner for Schneider PLCs
 * Mitsubishi: Simple Broadcast scanner for Mitsubishi PLCs, together with a broadcast State Changer for Mitsubishi
 * Beckhoff ADS Pwner & Route Spoofer: More details coming later (should've attended BruCON 0x0B ;-)
+* S7-300_password.py : Decrypt and Encrypt PLC passwords (captured while sniffing)
diff --git a/S7_300_Password.py b/S7_300_Password.py
new file mode 100644
index 0000000..a14d59c
--- /dev/null
+++ b/S7_300_Password.py
@@ -0,0 +1,123 @@
+
+'''
+	Copyright 2019 Tinus Umans(c)
+        This program is free software: you can redistribute it and/or modify
+        it under the terms of the GNU General Public License as published by
+        the Free Software Foundation, either version 3 of the License, or
+        (at your option) any later version.
+        This program is distributed in the hope that it will be useful,
+        but WITHOUT ANY WARRANTY; without even the implied warranty of
+        MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+        GNU General Public License for more details.
+        You should have received a copy of the GNU General Public License
+        along with this program.  If not, see <http://www.gnu.org/licenses/>.       
+        
+        File name S7_300_Password.py
+        written by tinus[dot]umans[at]ugent[dot]be
+		---
+		Decrypt en Encrypt Passwords found by sniffing network between TIA PORTAL and S7_300
+
+		Source of encryption algorithm :   https://www.slideshare.net/AlexanderTimorin/industrial-protocols-for-pentesters
+'''
+
+
+import os, binascii
+
+
+def Decrypt(Pass_in_Hex):
+	if len(Pass_in_Hex) != 16:
+		print("Hex string not long enough. Expected 8 bytes")
+		exit()
+	Pass_in_byte = [int(Pass_in_Hex[x*2:x*2+2],16) for x in range(0,8)]
+
+	# Decrypt
+	Pass_Result = []
+	Pass_Result.append( Pass_in_byte[0] ^ 0x55)
+	Pass_Result.append( Pass_in_byte[1] ^ 0x55)
+	for x in range(2, 8):
+		Pass_Result.append( Pass_in_byte[x]  ^ Pass_in_byte[x-2]  ^0x55)
+	return Pass_Result
+
+
+def Encrypt(Pass): 	
+	if len(Pass) > 8 :
+		print(" Password cannot exceed 8 characters")
+		exit()	
+	Pass_in_byte = [ord(c) for c in Pass]
+	while len(Pass_in_byte ) != 8:
+		Pass_in_byte.append(32)
+	# encryption
+	Pass_in_byte[0] = Pass_in_byte[0] ^ 0x55
+	Pass_in_byte[1] = Pass_in_byte[1] ^ 0x55
+	for x in range(2, 8):
+		Pass_in_byte[x] = Pass_in_byte[x]  ^ Pass_in_byte[x-2] ^ 0x55
+	# Show
+	return Pass_in_byte
+
+
+
+
+
+def GUI_Decrypt():
+	os.system('cls' if os.name == 'nt' else 'clear')
+
+	print("""
+[*********************************************************************************************************]"
+                                              Decrypt
+
+[*********************************************************************************************************]
+
+""")
+	Pass_in_Hex = input ("hex string to decrypt : ")
+	Pass_in_Hex = Pass_in_Hex.replace(" " , "")
+	Pass_Result = Decrypt(Pass_in_Hex)
+	# Show
+	print ("Decrypted pass ")
+	print( "", end = "==> ")
+	[ print(chr(c), end = ' ') for c in Pass_Result]
+	print("<==")
+
+
+def GUI_Encrypt():
+	os.system('cls' if os.name == 'nt' else 'clear')
+
+	print("""
+[*********************************************************************************************************]"
+                                              Encrypt
+
+[*********************************************************************************************************]
+
+""")
+	Pass = input ("Password to encrypt : ")
+	Pass_in_byte = Encrypt(Pass)
+	print ("Encrypted pass ")
+	print( "", end = "==> ")
+	[	print(hex(c).split('x')[-1] , end = ' ') for c in Pass_in_byte]
+	print("<==")
+
+
+def GUI_Main():
+	os.system('cls' if os.name == 'nt' else 'clear')
+	print ("""
+[*********************************************************************************************************]
+                                       --- S7-300 Password ---
+
+                                        Created By Tinus Umans(c) 
+                                 For more Industrial Security : www.ic4.be
+            
+[*********************************************************************************************************]
+	""")
+
+	print("1: Decrypt")
+	print("2: Encrypt")
+	print("q: Exit")
+	print()
+	iChoise = input("Option [q] :")
+	if iChoise == '1'	:	GUI_Decrypt()
+	elif iChoise == '2'	:	GUI_Encrypt()
+	else : exit()
+
+
+
+
+GUI_Main()