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| import os
import string
import signal
from gmpy2 import *
from Crypto.Util.number import *
from hashlib import sha256, sha512, md5
from random import randint, seed, choice
from SECRET import FLAG
class KGC:
def __init__(self, lam):
self.lam = lam
while 1:
self.z = 2 * randint(1 << 63, 1 << 64)
self.p = self.genPrime(self.z)
self.q = self.genPrime(2)
self.N = (self.z * self.p + 1) * (2 * self.q + 1)
self.s1, self.s2 = randint(1, self.N), randint(1, self.N)
if self.s1 % 2 == self.s2 % 2:
self.s1 += 1
self.g = randint(1, self.N)
check = pow(self.g, self.p * self.q, self.N) != 1 and pow(self.g, self.z * self.p, self.N) != 1 and pow(self.g, self.z * self.q, self.N) != 1
while not check:
self.g = randint(1, self.N)
check = pow(self.g, self.p * self.q, self.N) != 1 and pow(self.g, self.z * self.p, self.N) != 1 and pow(self.g, self.z * self.q, self.N) != 1
break
self.g1, self.g2, self.g3 = (pow(self.g, self.p * self.s1, self.N),
pow(self.g, self.p * self.s2, self.N),
pow(self.g, self.p ** 2, self.N))
def genPrime(self, delta):
prime = 1
while not isPrime(prime):
prime = delta * getPrime(self.lam // 2 - delta.bit_length()) + 1
return (prime - 1) // delta
def H1(self, m):
return int(sha256(m.encode()).hexdigest(), 16)
def H2(self, m):
return int(sha512(m.encode()).hexdigest(), 16)
def H3(self, m):
return int(md5(m.encode()).hexdigest(), 16)
def KeyGen(self, username):
h1, h2 = self.H1(username), self.H2(username)
y1 = invert(self.p, self.z * self.q) * h1 % (self.z * self.q)
y2 = invert(self.p, self.z * self.q) * h2 % (self.z * self.q)
d = invert(y1 * self.s1 + y2 * self.s2, self.z * self.q)
e = pow(self.g1, h1, self.N) * pow(self.g2, h2, self.N) % self.N
return (y1, y2, d, h1, h2, e)
def enc(self, m, user):
length_limit = 2**128
r = randint(1, self.N)
F = pow(self.g3, r, self.N)
c1 = (m % length_limit) ^ self.H3(str(F))
c2 = pow(user.e, r, self.N)
return (c1, c2)
def dec(self, c, user):
c1, c2 = c
F = pow(c2, user.d, self.N)
m = long_to_bytes(self.H3(str(F)) ^ c1)
return m
class USER:
def __init__(self, id_, kgc):
self.id_ = id_
self.y1, self.y2, self.d, self.h1, self.h2, self.e = kgc.KeyGen(id_)
def print_info(self):
print(f'e, d, h1, h2 = ({self.e}, {self.d}, {self.h1}, {self.h2})')
def register(username, kgc):
user = USER(username, kgc)
return user
def intercept():
while True:
try:
informant = 'WMCTF_IS_FUN_' + str(getRandomNBitInteger(512))
USERLIST[informant] = register(informant, kgc)
INFORMATION = randint(1 << 127, 1 << 128)
return informant, INFORMATION
except:
pass
def proof_of_work():
seed(os.urandom(8))
proof = ''.join([choice(string.ascii_letters + string.digits) for _ in range(20)])
digest = sha256(proof.encode()).hexdigest()
print("sha256(XXXX+%s) == %s" % (proof[4:], digest))
print('Give me XXXX: ', end = '')
x = input().strip()
if len(x) != 4 or sha256((x + proof[4:]).encode()).hexdigest() != digest:
return False
return True
def BANNER():
print(
'''
|--------------|
| [P]arams |
| [R]egister |
| [E]ncrypt |
| [D]ecrypt |
| [I]ntercept |
| [G]etflag |
|--------------|
''')
if __name__ == "__main__":
if not proof_of_work():
exit()
LAM = 512
LIMITED_USER_NUM = 6
kgc = KGC(LAM)
USERLIST = {}
informant, INFORMATION = intercept()
signal.alarm(5)
BANNER()
while True:
op = input('Input your choice please: ')
if op == 'P':
print(f'Here gives you some params about the KGC: {kgc.N}, ({kgc.g1}, {kgc.g2}, {kgc.g3})')
elif op == 'R':
if len(USERLIST) >= LIMITED_USER_NUM:
print('No more new registration allowed!')
continue
username = input('Input your name: ').strip()
try:
if username not in USERLIST:
USERLIST[username] = register(username, kgc)
print('Registration success, keep your account well!')
USERLIST[username].print_info()
else:
print('This username has been taken!')
except:
print('Registration Not Allowed!')
elif op == 'E':
username = input('Input your name: ').strip()
try:
if username in USERLIST:
message = input('Input your message in HEX: ').strip()
cipher = kgc.enc(int(message, 16), USERLIST[username])
print(f'Here is the ciphertext: {cipher}')
else:
print('This user does not exist!')
except:
print('Bad Request!')
elif op == 'D':
username = input('Input your name: ').strip()
prikey = input('Input your private key: ').strip()
try:
if username in USERLIST and USERLIST[username].d == prikey:
c1, c2 = input('Input ciphers(c1, c2) in HEX: ').strip()[1:-1].split(', ')[0:2]
c1, c2 = int(c1, 16), int(c2, 16)
m = kgc.dec((c1, c2), USERLIST[username])
print(f'Here is the message: {m}')
else:
print('Bad Request!')
except:
print('Bad Request!')
elif op == 'I':
CIPHER = kgc.enc(INFORMATION, USERLIST[informant])
print(f'Here you intercepted a piece of message {CIPHER} sent by {informant}...')
elif op == 'G':
message = str(input('Input right messages in HEX and you\'ll get your bonus: '))
try:
message = int(message, 16)
except:
print('Illegal input!')
continue
if INFORMATION == message:
print(f'Here is your flag: {FLAG}!')
else:
print('You really let me down..')
exit()
else:
print('Have a nice day!')
exit()
|