Day 17

Day 17/FasterKeyExchange.py

@@ -0,0 +1,76 @@
+import secrets
+import hashlib
+from base64 import b64encode
+from Crypto.Cipher import AES
+from Crypto.Util.Padding import pad
+
+g = 3
+p = 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
+
+class Server():
+    def __init__(self, port=3331):
+        self.port = port
+        self.fKE = FasterKeyExchange(g, p)
+        self.y_server = self.fKE.calculate_y()
+        self.y_client = 0
+        self.IV = "d724c349c2b28831"
+        self.key = "313371337"
+
+    def print_banner(self):
+        print("       ---_ ......._-_--.")
+        print("      (|\ /      / /| \  \\")
+        print("      /  /     .'  -=-'   `.")
+        print("     /  /    .'             )")
+        print("   _/  /   .'        _.)   /")
+        print("  / o   o        _.-' /  .'")
+        print("  \          _.-'    / .'*|")
+        print("   \______.-'//    .'.' \*|")
+        print("    \|  \ | //   .'.' _ |*|")
+        print("     `   \|//  .'.'_ _ _|*|")
+        print("      .  .// .'.' | _ _ \*|")
+        print("      \`-|\_/ /    \ _ _ \*\\")
+        print("       `/'\__/      \ _ _ \*\\")
+        print("      /^|            \ _ _ \*")
+        print("     '  `             \ _ _ \\")
+        print("                       \_")
+        print("Challenge by pyth0n33. Have fun!")
+        
+    def run(self):
+        self.print_banner()
+        input("Enter to start")
+        print("\x1b[2J\x1b[H")
+        print("Here's my y={0}\n\n".format(self.y_server))
+        self.y_client = int(input("Now give me your y please: "))
+        self.key = str(self.fKE.calculate_key(self.y_client))
+        self.iv = self.key[0:16]
+        self.encrypt()
+
+    def encrypt(self):
+        key = bytes(hashlib.md5(bytes(self.key, "utf-8")).hexdigest(), "utf-8")
+        cipher = AES.new(key, AES.MODE_CBC, iv=bytes(self.iv, "utf-8"))
+        cipher_text_bytes = cipher.encrypt(pad(b"The Advanced Encryption Standard (AES), also known by its original name Rijndael, is a specification for the encryption of electronic data established by the U.S. National Institute of Standards and Technology (NIST) in 2001.", AES.block_size))
+        print(b64encode(cipher_text_bytes))
+        
+class FasterKeyExchange():
+    def __init__(self, g, p):
+        self.g = g
+        self.p = p
+        self.x = self.get_random_x()
+
+    def get_random_x(self):
+        return secrets.SystemRandom().randint(g, p-2)
+    
+    def calculate_y(self):
+        return (self.g * self.x) % self.p
+
+    def calculate_key(self, y):
+        return (y * self.x) % self.p
+
+if __name__ == "__main__":
+    server = Server()
+    server.run()
+        
+        
+
+
+    

Day 17/decode.py

@@ -0,0 +1,43 @@
+#!/usr/bin/python
+
+import base64
+import hashlib
+from Crypto import Random
+from Crypto.Cipher import AES
+
+def linear_diophantine_equation(a, b):
+    if b > a:
+        return linear_diophantine_equation(b, a)
+
+    if b == 0:
+        return a, 1, 0
+
+    d, x, y = linear_diophantine_equation(b, a % b)
+    return (d, y, x - (a // b) * y)
+
+a = 17577019968135092891915317246036083578063875217491307011102321322815719709605741738459191569497548099944025771002530369133716621942963853230082186943938164591230020725702755002287589522851172217336150522367152517270250629688405924844750026155547199020780202996200555426652190631837288299999083335649923708175859594750237448640513280683859296367607523542293538555215282798100455110266565881599829107971869244773384413618546118850868579583095489023778055976570366853411496753062216229293710557686212314300848121614558806328788578096144576605248971916454783615989429937555579437307320472405217413938048149254574677430624
+
+b = 15228628318558071728245462802366236848375416102820239825350329247148900182647243994904519787528142824353837070194785550898962097219309344881183948914850354340893035399529028331238911753358245357848436203268982345430735846016484221944423499956958406189854969330305125479065873712331269870135028162018087451460656203085824963123310757985362748654204595136594184636862693563510767025800252822776154986386637346156842972134635578534633722315375292616298410141343725683471387328655106920310236007034951004329720717533666052625540760911360823548318810161367913281234234193760867208897459774865037319252137821553407707977377
+
+g = 3
+p = 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
+
+message = "jqMYIn4fzSqzIXArwJm/kPitNhf4lwhL0yPRKpF+NYXyPmhoEwNG/k2L5vCZqFWNPvTzisnu93/8uK/PZnnCGg=="
+messageDecoded = base64.b64decode(message)
+
+def test_x(x):
+    return (g * x) % p == a
+
+# (g * x) % p = a
+# (g * x) - (k * p) = a
+
+x = linear_diophantine_equation(g, p)[2] * a
+key = str((b * x) % p)
+iv = key[0:16]
+
+# Decrypt
+key = bytes(hashlib.md5(bytes(key, "utf-8")).hexdigest(), "utf-8")
+cipher = AES.new(key, AES.MODE_CBC, iv=bytes(iv, "utf-8"))
+plain_text_bytes = cipher.decrypt(messageDecoded)
+plain_text = plain_text_bytes.decode("utf-8")
+print(plain_text)