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Crypto 4

Crypto 4

  • 📚 Category: Crypto
  • 🎯 Points: 100
  • 📝 Description: Use flagCheck to input the flag you get from the challenge to get the actual flag

✍️ Writeup

We one file: 

chall.txt


Cipher text: VGhhdCBtZWV0aW5nIHdhcyBhIGxpdHRsZSBjcmF6eS4gV2UgaGF2ZSBubyBpZGVhIHdoZXJlIHRob3NlIGd1eXMgaW4gdGhlIGJsYWNrIHN1aXRzIGNhbWUgZnJvbSwgYnV0IHdlIGFyZSBsb29raW5nIGludG8gaXQuIFVzZSB0aGUga2V5IGluZmlsdHJhdGlvbiBmb3IgbmV4dCB3ZWVrknMgbWVldGluZy4gU3RheSB3aXRoIHRoZSBjYXVzZSBhbmQgd2Ugd2lsbCBzdWNjZWVkLg==

Let's decrypt it.

import base64

text= "VGhhdCBtZWV0aW5nIHdhcyBhIGxpdHRsZSBjcmF6eS4gV2UgaGF2ZSBubyBpZGVhIHdoZXJlIHRob3NlIGd1eXMgaW4gdGhlIGJsYWNrIHN1aXRzIGNhbWUgZnJvbSwgYnV0IHdlIGFyZSBsb29raW5nIGludG8gaXQuIFVzZSB0aGUga2V5IGluZmlsdHJhdGlvbiBmb3IgbmV4dCB3ZWVrknMgbWVldGluZy4gU3RheSB3aXRoIHRoZSBjYXVzZSBhbmQgd2Ugd2lsbCBzdWNjZWVkLg=="

print(base64.b64decode(text))

b'That meeting was a little crazy. We have no idea where those guys in the black suits came from, but we are looking into it. Use the key infiltration for next week\x92s meeting. Stay with the cause and we will succeed.'

Let's check with flagCheck

hacker@csawctf2011~crypto-100-4:/challenge$ ./flagCheck
Enter the flag: infiltration
Correct flag!
pwn.college{REDACTED}