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Day 17

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Roman Hergenreder 2018-12-17 09:04:15 +01:00
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commit cd683fdf17
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Day 17/FasterKeyExchange.py Normal file
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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()

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Day 17/decode.py Normal file
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#!/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)