TeamH4C Writeup


This post contains the writeups for:

Did you read the Rules?

Find the flag

The Easiest problem of the universe



Did you read the rules

The question says it all


1. The competition begins at 5 p.m. on October 9, 2020 and ends at 5 p.m. on October 10, 2020 KST. Late flag authentication will be excluded from the total score. D0_You
2. You can participate in this competition only as an individual, and only individual participants are qualified to receive the prize. The ID assumed to be a team will be excluded from the final ranking and you will not be able to receive the prizes. _C_
3. From 1st to 6th place, write-up must be submitted to TeamH4C’s official email with your real name and phone number until Monday, October 15, 11:59 p.m KST. (e-mail: Wh4t_1
4. Disqualification or punishment will be made when abnormal access to the server, attacks, or all kinds of inappropriate manipulation are detected on the platform.
5. After the Write-up examination, the potential recipients must submit their phone number for authentication. The organizing team will give the prize only after the phone call with the recipients. _c?
If we cannot reach you one way or another, your qualifications of being rewarded will be transferred to the next ranked person.
6. Report of any inconvenience or unexpected vulnerability is welcomed.
7. Disqualification or other measures can be taken anytime to an event in which the management may judge that it is unfair.

Thank you.


So the flag for this question is h4c(D0_You_C_Wh4t_1_c?)





Find the flag

The downloaded file called contains Hangul.png upon unzipping. The image consists of another zip file which can be seen with the help of binwalk. Upon unzipping Hangul.png another file called Hangul is retrieved which contains the flag for this question.

The flag is h4c(i_1ove_hangul)





The Easiest problem of the universe


I used cyberchef to decrypt the given string under the option of base64. This operation upon being executed thrice gave me the following string.

_-_-_-__ _–__-_- _–____- _–_–_- _-__-___ __–_-__ _-____–


This is binary encoded and thus I changed the hyphens and underscores to 0 and 1.

Taking – as 0 and _ as 1 the output was as follows.

10101011 10011010 10011110 10010010 10110111 11001011 10111100

But by converting this to ascii it didnt made any sense. So onward to the next approach.


Taking – as 0 and _ as 1 I received the flag for this question

01010100 01100101 01100001 01101101 01001000 00110100 01000011

Binary to ascii – TeamH4C


So the flag is h4c(TeamH4C)