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爆裂流星！！！！ Burst meteor!!!!
二十以內的加法對小學生來說有點難了，對高中生來說有點簡單了，對大學生來說剛剛好！！！ 誒，所以全對以後的獎勵呢？？？ Adding up to 20 is a bit difficult for elementary school students, a bit simple for high school students, and just right for college students!!! Hey, so what about future rewards???
"Some"body once claimed "the father of 4", but I have been hunting for the true number behind binary. Finally, I see the pattern. "syscall" is 0f05 (15, 5). '\n' is 10. "ret" is 0xc3 (195). These vital instructions are all multiples of 5. Therefore, 5 is the master of binary, and I have named the code "the child of 5". Do you have what it takes? Show me your childcode.
smaller
這是個能夠讀取文件的程序，來看看有沒有你想要的文件吧o(￣▽￣)ブ。 This is a program that can read files. Let's see if there are any files you want o(￣▽￣)ブ.
這是個能夠讀取文件的程序，來看看有沒有你想要的文件吧o(￣▽￣)ブ。 This is a program that can read files. Let's see if there are any files you want o(￣▽￣)ブ.
衰了，唔單文件冇佐，伺服器的shell也連不上了，只剩下一個服務還在運行。 Decline, not only files are missing, but also the server's shell I can't connect anymore, only one service is still running.
piano, pianissimo, pianississimo
The challenge environment will execute the following command to set up a restricted execution context: /chroot --userspec=1000:1000 /home/ctf /run.sh#!/bin/sh ./qjs ./tmp.js
You'd better stop and leave right now.
那麼問題來了，什麼是copper？ So the question is, what is copper?
我最近開始迷上數學了，但這題看起來真的很複複複雜，你能幫我嗎？ I've recently become obsessed with math, but this problem seems really comcomplexx. Can you help me?
密碼學很簡單！祝你玩得開心！ Crypto is so EC! May you have fun!
Easy ECC...and LWE maybe
沒有那個n，我照樣可以解出flag。 Even without that n, I can still solve the flag.
Easy AES Challenge
我實現了一個使用三個密鑰的分組密碼算法。 I implemented a block cipher algorithm that uses three keys.
e這麼大...何意味？ E is so big... what does it mean?
cute rsa? oh nonono, so cruel
Chimedal帶上了99朵玫瑰，決定向心心念念的女神表白，可女神卻給了他一張小紙條，上面是一段奇奇怪怪的資訊，如果Chimedal能破解這段資訊的話，女神就答應跟他在一起。作為Chimedal最好的朋友的你，能否幫Chimedal抱得美人歸呢？ 請注意：flag需要添加flag{}后提交，flag包含下劃綫
“_”和空格“ ”Chimedal brought 99 roses, determined to confess to the goddess he had been longing for. However, the goddess gave him a small note containing a strange message. If Chimedal could decipher this message, she would agree to be with him. As Chimedal's best friend, can you help him win the heart of his beloved? Please note: The flag needs to be submitted after adding flag{} and the flag contains underscore (_) and space ( )
Despite taking the fastest action, the suspect still noticed us and cleared the evidence from the computer before we arrived. Please help us find as many useful clues as possible. Attachment password:
==###HkCert2025###==Note:
- Answer all of question with UTC+8 timezone.
- When you need to work with the registry, please be careful not to overwrite your machine's registry. You can also perform the analysis in a virtual machine. The attachment link is as follows: https://drive.google.com/file/d/1DM14noGC5YdBb4gGmPX41gM4MLlvoYZS/view?usp=sharing MD5 hash of attachment.zip: 7f559bb45323d512cf65c384009b4f31
新人，學院給了你一套能殺死龍王的武器，但上面的文字好像有點看不清啊（flag格式為：flag{xx_xx}） Newcomer, the academy has given you a set of weapons capable of killing the Dragon King, but the text on them seems a bit hard to read (flag format: flag{xx_xx})
看起來我的模型有過擬合的情況。你能幫我看看嗎？ It seems like my model is overfitting. Can you take a look for me?
Oh, the music stopped! Alright everyone — clap along and follow my lead! We'll keep it going together!
Healx has developed a personal health assistant app and has decided to hire a senior AI safety expert to test the app before its launch.
Try to Talk With Private Protocol
問卷連結/Questionnaire Link: https://forms.hkcert.org/hkcertctf2025-evaluation Please note that there should be no spaces in the submitted flag.The flag format is ctf2025{}
We captured a suspicious file transmitted through a covert channel, analyzed it and found out the secrets. The flag format is hkcert25{}
A device has been implanted with a backdoor, attempting to trigger it and leak sensitive information.
Very easy pickle jail，go ahead !
怎麽有的函數看不到 Why can't some functions be seen
Have you heard of wasm
bc文件是什麽 bc What is the file
Hello, I found a box. Could you open it
一個簡單的驅動。 A simple driver. 注：
- flag提交格式：flag{youget}
- 如果系統出現藍屏，請確保自身環境純淨，本驅動不會對系統進行任何破壞性操作，盡請放心。
- 解題推薦使用64位Win10 - Win11 22H2的虛擬機系統。 Note:
- flag Submission format: flag{youget}
- If the system shows a blue screen, please ensure that your environment is pure. This driver will not perform any destructive operations on the system, so please rest assured.
- Recommended use of 64 bit for problem-solving Win10 - Win11 22H2 The virtual machine system.
Reverse engineering a simple algorithm
Reverse a simple algorithm
開始考察數據結構 Start investigating data structures
隨機密鑰怎麽辦？ What about the random key? flag提交格式：flag{youget} flag Submission format: flag{youget}
鑰匙找不到了 I can't find the key
需要解密哦 We need to decrypt it
“This is a simple file upload service. The administrator said, ‘I hate the letter “P”. Anything containing “P” is not allowed in!’”
“The magnificent CloudBeaver stands guard over the torrent of data.”
Welcome to the labyrinth of serialization. There are no familiar Roman roads or spring gardens here—only high walls all around. Find the hidden ‘tracking’ path, and only then can you break free from the maze.
A Lua online executor
Come and try some code auditing!
We've developed an advanced AI data processing system that can intelligently process data from any URL. The system is already deployed on a server; can you find the hidden flag within it?
Let’s do a code audit.
Bill Jobs developed an intelligent login system, but there is a vulnerability in one of the Header headers for the login. Can you help him find the vulnerability? This is a beneficial behavior for the body.
object reference and pointer reference
The developer jumped on the trend and used the latest Next.js 15 to build the application.
“I wrote a simple page to render your name.”