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2021DASCTF八月挑戰賽WP2.[crypto]easymath3.寒王’sblog4.stealer

1.簽到

略。

2.[crypto]easymath

參考:https://zhuanlan.zhihu.com/p/363648238

https://blog.csdn.net/song_lee/article/details/107498149

exp:

s_shift = 1862790884563160582365888530869690397667546628710795031544304378154769559410473276482265448754388655981091313419549689169381115573539422545933044902527020209259938095466283008
len_s = 175
five_power = 5 ** len_s
from Crypto.Util.number import *
import gmpy2
s = s_shift * gmpy2.powmod(2, -10000, five_power) % five_power
print(s)
print(long_to_bytes(s))
           

3.寒王’sblog

這題需要腦洞,腦洞通路https://hanwang2333.gitee.io/2020/03/12/outguess/flag.jpg

得到flag.jpg:

2021DASCTF八月挑戰賽WP2.[crypto]easymath3.寒王’sblog4.stealer

然後照着教程走:

2021DASCTF八月挑戰賽WP2.[crypto]easymath3.寒王’sblog4.stealer
2021DASCTF八月挑戰賽WP2.[crypto]easymath3.寒王’sblog4.stealer

4.stealer

這題把流量包打開基本沒啥發現,倒是DNS的包裡看到有資料:

2021DASCTF八月挑戰賽WP2.[crypto]easymath3.寒王’sblog4.stealer

看到IVBOR開頭盲猜是圖檔base64:

2021DASCTF八月挑戰賽WP2.[crypto]easymath3.寒王’sblog4.stealer

這裡把所有的base64提取出來:

把多餘的字元去掉得到:

ctf