## 3kCTF-2021 Writeup

We are united to play 3kCTF-2021 and result in the second place. In this blog post, we will walk through our solutions on the challenges solved....

We are united to play 3kCTF-2021 and result in the second place. In this blog post, we will walk through our solutions on the challenges solved....

We played Cyber Apocalypse 2021 and I have attempted several crypto challenges. I'll include the challenges Wii Phit and Hyper Metroid in this writeup....

Lost in Your Eyes is a reverse engineering challenge in DiceCTF 2021 with ten solves (334 points). We are given a binary which takes an input and outputs either :) or :(. If you win a smiley face on the remote server, you are additionally given the flag....

TetCTF is the first CTF I have played in 2021. I recalled from last year that they have cool challenges. This year, there are three crypto challenges. In particular, unevaluated is the hardest among them. Although I did not solve them, I dug into rabbit holes and had a lot of struggle, uh, fun. Challenge Summary There is a 128-bit prime $p$. Define $\cdot: \mathbb{Z}_{p^2}^2\times\mathbb{Z}_{p^2}^2\rightarrow\mathbb{Z}_{p^2}^2$ by \[(x_1, y_1)\cdot(x_2, y_2) := \left(\left(x_1x_2-y_1y_2\right)\ \text{mod}\ p^2, \left(x_1y_2+y_1x_2\right)\ \text{mod}\ p^2\right),\]...

I was teamed up to play hxp CTF as @blackb6a last week. The hxp team had come up with a collection of hard challenges. In particular, there are two series of crypto challenges with a total of five parts. I will be writing on the hyper challenge and some follow-up and unanswered questions regarding to hyperelliptic curves. ⓘ 𝗢𝗳𝗳𝗶𝗰𝗶𝗮𝗹 𝘀𝗼𝘂𝗿𝗰𝗲𝘀 𝘀𝘁𝗮𝘁𝗲𝗱 𝘁𝗵𝗮𝘁 𝘁𝗵𝗶𝘀 𝗶𝘀 𝗺𝗶𝘀𝗹𝗲𝗮𝗱𝗶𝗻𝗴 Seriously. I knew nothing on hyperelliptic curves prior to the CTF....

Dragon CTF 2020 is definitely had my best CTF moments. There are big brain moments and I have been mind-blown for multiple times during the game. This time we have teamed up with @blackb6a. I have solved all the crypto challenges and two challenges with my teammates. There are three challenges writeup in this post: Bit Flip (parts 2 and 3) Frying in motion babykok Bit Flip (Crypto, 155+324+343 points) Solved by Mystiz....

urlcheck v1 (Web, 98 points) Solved by Ozetta. Objective: SSRF http://127.0.0.1/admin-status The input needs to fulfil the pattern '\A(\d+)\.(\d+)\.(\d+)\.(\d+)\Z' and the first octet cannot be 0 or 127, and some other patterns for internal IP addresses. For some reason, int("0177") is still 177 instead of 127 in Python, so we can use http://0177.0.0.1/admin-status urlcheck v2 (Web, 128 points) Solved by Ozetta. Objective: SSRF http://localhost/admin-status Standard TOCTOU bug, just use DNS rebinding to get access: http://23bbd91c....

This week, we have teamed up as @blackb6a to play CONFidence 2020 CTF. We end up ranked 15, but we are more proud of ourselves able to solve a reversing challenge called Team Trees (395 points, 5 solves). In particular, we are the first-to-solve to the challenge. It took us around two hours to win the flag. This writeup is written by @harrier_lcc and @mystiz613. Challenge Summary We wanted to plant a lot of trees, but it's going kinda slow....

I was teamed-up with @blackb6a on Google CTF this time. I have solved 7 challenges alone and 3 challenges with my teammates. In particular, Oracle is a crypto challenge with 13 solves. It has got me spending 12 hours. All in all, it was a great experience in terms of learning, but my liver hurts. This piece of writeup may be very computation intensive, just because I would like to make everything clear....

reporter (Web; 498 points) Solved by apple. Author: rekter0 Reporter is an online markdown reporting tool. it's free to use for everyone. there's a secret report we need located here source Walkthrough The application provide markdown hosting service and it will automatically download and embed external images (or any files) to the 'report'. There are 4 buttons on the interface: Edit, Preview, Save, and Deliver. The first target of the challenge is to access the secret_report....