2020 HGAME

#!/usr/bin/env python3
from secret import flag
assert flag.startswith(b'hgame{') and flag.endswith(b'}')
m = int.from_bytes(flag, byteorder='big')
p = 681782737450022065655472455411
q = 675274897132088253519831953441
e = 13
c = pow(m, e, p*q)
assert c == 275698465082361070145173688411496311542172902608559859019841

import gmpy2
from Crypto.Util.number import long_to_bytes
p = 681782737450022065655472455411
q = 675274897132088253519831953441
e = 13
phi = (p-1)*(q-1)
d = gmpy2.invert(e,phi)
n = p*q
c = 275698465082361070145173688411496311542172902608559859019841
print long_to_bytes(pow(c,d,n))
# hgame{t3Xt6O0k_R5A!!!}

import gmpy2

TABLE = 'zxcvbnmasdfghjklqwertyuiop1234567890QWERTYUIOPASDFGHJKLZXCVBNM'
MOD = len(TABLE)
#这一步求A和B
flag = "hgame"
for A in range(0xff):
for B in range(0xff):
cipher = ''
for b in flag:
i = TABLE.find(b)
ii = (A*i+B)%MOD
cipher += TABLE[ii]
if(cipher=='A8I5z'):
print A, B, cipher
break
A = 13
B = 14
c = 'zxcvbnmasdfghjklqwertyuiop1234567890QWERTYUIOPASDFGHJKLZXCVBNM'
flag = ''
cipher = "A8I5z{xr1A_J7ha_vG_TpH410}"
for b in cipher:
o = TABLE.find(b)
if o==-1:
flag += b
continue
for x in c:
i = TABLE.find(x)
ii = (A*i+B)%MOD
now = TABLE[ii]
if now==b:
flag+=x
break
print flag

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
import os, random
import string, binascii, base64
from secret import flag
assert flag.startswith(b'hgame{') and flag.endswith(b'}')
flag_len = len(flag)

def xor(s1, s2):
    #assert len(s1)==len(s2)
    return bytes( map( (lambda x: x[0]^x[1]), zip(s1, s2) ) )

random.seed( os.urandom(8) )
keystream = ''.join( [ random.choice(string.ascii_letters+string.digits) for _ in range(flag_len) ] )
keystream = keystream.encode()
print( base64.b64encode(xor(flag, keystream)).decode() )

import base64,string
from pwn import *
context.log_level = 'debug'
cipher = []
for i in range(40):
p = remote("47.98.192.231","25001")
s = p.recv(500)
cipher.append(s)
p.interactive()

t = (string.ascii_letters + string.digits).encode()
res = (string.printable).encode()
for i in range(len(base64.b64decode(cipher[0]))):
l = set()
for c1 in cipher:
for c2 in cipher:
d1 = base64.b64decode(c1)
d2 = base64.b64decode(c2)
if d1==d2:
continue
re = set()
tmp1 = d1[i]^d2[i]
for j in range(len(t)):
for k in range(len(t)):
if j==k:
continue
tmp2 = t[j]^t[k]
#找到了c1 c2 m1 m2都是可见字符，把符合条件的k放进去
if tmp1==tmp2:
re1 = int(d2[i]^t[j]).to_bytes(1,'big')
re2 = int(d2[i]^t[k]).to_bytes(1,'big')
if res.find(re1)!=-1:
re.add(re1)
if res.find(re2)!=-1:
re.add(re2)
if(l==set()):
l = re
else:
tmp = l.intersection(re)
if tmp!=set():
l.intersection_update(re)
else:
l.update(re)
print i,''.encode().join(l)
#hgame{r3us1nG+M3$5age-&&~rEduC3d_k3Y-5P4Ce}