#inctf2021
import os, hashlib, pickle
from Crypto.Cipher import AES
from Crypto.Util.Padding import pad, unpad
key = os.urandom(4)
FLAG = open('flag.txt', 'rb').read()
p = 0xFFFFFFFF00000001000000000000000000000000FFFFFFFFFFFFFFFFFFFFFFFF
a = p - 3
b = 0x5AC635D8AA3A93E7B3EBBD55769886BC651D06B0CC53B0F63BCE3C3E27D2604B
def gen_key(G, pvkey):
G = sum([i*G for i in pvkey])
return G
def encrypt(msg, key):
key = hashlib.sha256(str(key).encode()).digest()[:16]
cipher = AES.new(key, AES.MODE_CBC, os.urandom(16))
return {'cip': cipher.encrypt(pad(msg, 16)).hex(), 'iv': cipher.IV.hex()}
def gen_bob_key(EC, G):
bkey = os.urandom(4)
B = gen_key(G, bkey)
return B, bkey
def main():
EC = EllipticCurve(GF(p), [a, b])
G = EC.gens()[0]
Bx = int(input("Enter Bob X value: "))
By = int(input("Enter Bob Y value: "))
B = EC(Bx, By)
P = gen_key(G, key)
SS = gen_key(B, key)
cip = encrypt(FLAG, SS.xy()[0])
cip['G'] = str(G)
return cip
if __name__ == '__main__':
cip = main()
pickle.dump(cip, open('enc.pickle', 'wb'))
