36D杯--记录_ctfshow 36d杯你没见过的注入

rsaEZ

公钥解析，得到e、n以及得到c1、c2、c3，分别打印三个m即可，最后找出属于flag的部分：

from Crypto.PublicKey import RSA
from Crypto.Util.number import *
import gmpy2
 
publickey = RSA.importKey(open(r'C:\Users\lenovo\Desktop\public.key','rb').read())
e = publickey.e
n = publickey.n
p = 302825536744096741518546212761194311477
q = 325045504186436346209877301320131277983
c1 = bytes_to_long(open(r'C:\Users\lenovo\Desktop\encrypted.message1','rb').read())
c2 = bytes_to_long(open(r'C:\Users\lenovo\Desktop\encrypted.message2','rb').read())
c3 = bytes_to_long(open(r'C:\Users\lenovo\Desktop\encrypted.message3','rb').read())
 
d = gmpy2.invert(e,(p-1)*(q-1))
m1 = pow(c1,d,n)
m2 = pow(c2,d,n)
m3 = pow(c3,d,n)
print(long_to_bytes(m1))
print(long_to_bytes(m2))
print(long_to_bytes(m3))
#flag{3b6d3806-4b2b-11e7-95a0-000c29d7e93d}

justShow

看着冒号后面的，看起来就是把a移到了最后，应该是凯撒，得到：

gkbfnxeripjmxhemoc:abcdefghijklmnopqrstuvwxyz，看了wp才知道是playfair，冒号后面的就是key，但这里的key中i、j都有，26位，所以这里不需要用i代替j了，解出flag：

flagisctfshowicome