INCTFJ 2021 Writeup

Misc

Askey

Difficulty: Beginner

Content of file given with the challenge

Those numbers are binary. So I converted them to decimals and got some ascii values. So I converted those numbers to characters using python. Here is the python code for doing all these:

with open("chall", "r") as f:  # Opens the file for reading
    lines = (
        f.read().strip().split("\n")
    )  # Reads content of the file and split it by newline character

flag = ""
for num in lines:  # Iters through all of the lines in lines
    flag += chr(
        int(num, 2)
    )  # int(num, 2) converts num to decimal from binary and then chr() turns it into a character
print(flag)

Crack 1t

Message to crack: bafe38f09170ebc16dad1bbf11fe55a4

I put it in crackstation and crackstation showed me the message which was Hackerboy. Wrap it up with inctfj{} to get the flag.

Glyphy Tweet

Difficulty: Beginner

Message given with the challenge:

Ｔwіttｅr ⅰs a ｓｏcｉａｌ meｄｉa sⅰｔｅ， aｎd іｔs ｐｒіｍaｒy pｕｒposｅ ⅰｓ ｔо сοｎｎｅϲt ｐeоｐlｅ ａｎｄ allοw pｅοplｅ ｔο ｓｈａｒe thｅіｒ tｈｏｕｇｈｔs ｗｉｔｈ a ｂⅰg ａｕｄіｅｎce． Tｗⅰtｔeｒ ａｌlоwｓ users to discover stories regarding today's biggest news and events, follow people or companies that post content they enjoy consuming, or simply communicate with friends. Additionally, PR teams and marketers can use Twitter to increase brand awareness and delight their audience.

This message was encrypted with Twitter Secret Message. So just go to https://injecti0n.github.io/tweet-hidden-message/ and paste the message and voila! you get the decoded message. Just wrap the decoded message you got with inctfj{} to get the flag.

Mimmic

Difficulty: Beginner

File provded with the challenge: 0_0.txt
Note: You need to download it and view it in a text editor to view it properly.

The message given with the challenge was encoded with spam mimic with spaces. Go to https://www.spammimic.com/decodespace.cgi and decode it. Then you will get a pastebin link. Go to that link and you will get your flag.

Roter

Difficulty: Beginner

Message to decode: chwnzd{linunyfynnylmzilzoh}

The message is encrypted with caesar cipher. But it's simple to crack it. Just run this command:

for i in {1..25}; do echo "chwnzd{linunyfynnylmzilzoh}" | caesar $i; done

This would check all the keys and print their result. Here we could see the flag in the output. Now all left for you is to submit it!

XeroX

Files given with the challenge

I stumbled upon this challenge for a little bit thinking the goal was to xor the images. But then the hint said to see the difference. So I made a python script to find the difference between these 2 files and got the flag. Here is the script I wrote:

with open("1.jpg", "rb") as f:
    img_1 = f.read()

with open("2.jpg", "rb") as f:
    img_2 = f.read()

flag = ""
for c1, c2 in zip(img_1, img_2):
    if c1 != c2:
        flag += chr(c1)

print(flag)