nullcon HackIM 2016 -- Crypto Question 5

Now you are one step away from knowing who is that WARRIOR. The Fighter who will decide the fate of war between the 2 countries. The Pride of One and Envey of the Other... You have got the secrete file which has the crucial information to identify the fighter. But the file is encrypted with a RSA-Private key. Good news you have its corresponding public key in a file. Bad news there are 49 other keys. Whos is the Fighter.

crypto5.zip

我是在windows下在进行操作的，由于我安装了 git, 然后里面有 Git bash, 进入bash后有awk。

进入cmd,进bash

cmd> bash

用awk分出每一个key

bash-3.1$ awk '/BEGIN PUBLIC KEY/{n++}{print >"key" n ".txt" }' all_keys.txt

然后一个perl脚本：

for($i=1;$i<50;$i++){
    system("openssl rsautl -inkey key$i.txt -pubin -in warrior.txt >> outx.txt");
}

perl脚本后，打开 outx.txt 文件，得到：

This fighter is a designation for two separate, heavily upgraded derivatives of the Su-35 'Flanker' jet plane. They are single-seaters designed by Sukhoi(KnAAPO).

Google:Sukhoi(KnAAPO) Fighter, 得到 flag: Sukhoi Su-35