buuctf rsa

下载解压后是一个.key文件和一个.enc文件，不明白是什么意思，看wp是一道Crypto的题

https://www.cnblogs.com/Mayfly-nymph/p/11576913.html

.key是公钥，.enc是加密后的文件，利用.key文件找出e,d,p,q，再脚本解密rsa加密文件.enc即可

用记事本打开.key文件获得公钥

http://tool.chacuo.net/cryptrsakeyparse
在此页面对获得的公钥进行分解，得到指数和模数

 

C0332C5C64AE47182F6C1C876D42336910545A58F7EEFEFC0BCAAF5AF341C

 转换成十进制：86934482296048119190666062003494800588905656017203025617216654058378322103517

http://www.factordb.com/index.php?
通过该网页分析p、q

 

p:285960468890451637935629440372639283459

q:304008741604601924494328155975272418463

写脚本

import gmpy2
import rsa

e = 65537
n = 86934482296048119190666062003494800588905656017203025617216654058378322103517
p = 285960468890451637935629440372639283459
q = 304008741604601924494328155975272418463

phi=(p-1)*(q-1)
d=gmpy2.invert(e,phi)

key = rsa.PrivateKey(n, e, int(d), p, q)

with open("D:\\火狐下载\\CTF\\output\\flag.enc", "rb+") as k:
    k = k.read()
    print(rsa.decrypt(k, key))