[CryptoHack] Introduction to CryptoHack

https://cryptohack.org/challenges/introduction/

CryptoHack – Home

 

 

Finding Flags

Each challenge is designed to help introduce you to a new piece of cryptography. Solving a challenge will require you to find a "flag".

These flags will usually be in the format crypto{y0ur_f1rst_fl4g}. The flag format helps you verify that you found the correct solution.

Try submitting this into the form below to solve your first challenge.

진행방식을 설명해주는 첫번째 문제 !

문제에 나와있는 플래그를 그대로 입력하면 해결

 

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Great Sankes

Modern cryptography involves code, and code involves coding. CryptoHack provides a good opportunity to sharpen your skills.

Of all modern programming languages, Python 3 stands out as ideal for quickly writing cryptographic scripts and attacks. For more information about why we think Python is so great for this, please see the FAQ.

Run the attached Python script and it will output your flag.

Challenge files: - great_snakes.py

#!/usr/bin/env python3

import sys
# import this

if sys.version_info.major == 2:
    print("You are running Python 2, which is no longer supported. Please update to Python 3.")

ords = [81, 64, 75, 66, 70, 93, 73, 72, 1, 92, 109, 2, 84, 109, 66, 75, 70, 90, 2, 92, 79]

print("Here is your flag:")
print("".join(chr(o ^ 0x32) for o in ords))​

결국 문제는 마지막줄 !

" Run the attached Python script and it will output your flag. "

아래 파이썬 코드를 실행하면 플래그가 나온다

 

 

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Network Attacks

Several of the challenges are dynamic and require you to talk to our challenge servers over the network. This allows you to perform man-in-the-middle attacks on people trying to communicate, or directly attack a vulnerable service. To keep things consistent, our interactive servers always send and receive JSON objects.

Python makes such network communication easy with the telnetlib module. Conveniently, it's part of Python's standard library, so let's use it for now.

For this challenge, connect to socket.cryptohack.org on port 11112. Send a JSON object with the key buy and value flag.

The example script below contains the beginnings of a solution for you to modify, and you can reuse it for later challenges.

Connect at nc socket.cryptohack.org 11112

Challenge files:
  - telnetlib_example.py

#!/usr/bin/env python3

import telnetlib
import json

HOST = "socket.cryptohack.org"
PORT = 11112

tn = telnetlib.Telnet(HOST, PORT)


def readline():
    return tn.read_until(b"\n")

def json_recv():
    line = readline()
    return json.loads(line.decode())

def json_send(hsh):
    request = json.dumps(hsh).encode()
    tn.write(request)


print(readline())
print(readline())
print(readline())
print(readline())


request = {
    "buy": "clothes"
}
json_send(request)

response = json_recv()

print(response)​

 

주어진 파일에서 request 객체에 buy 키에 flag라는 값으로 바꿔주면 된다.

 

...

request = {
    "buy": "flag"
}

...

 

 

FLAG

crypto{sh0pp1ng_f0r_fl4g5}