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Daily AlpacaHack

A daily CTF challenge with a fun new puzzle every day

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We publish one simple, beginner-friendly or educational CTF challenge every day!

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Solve within 24 hours of release to appear on the leaderboard.

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Today's Challenge
shiragishiragi
AlpacaForm
Rev
Medium
22 solves
Submissions (latest 3)
ntanaka

SOLVED!

May 27, 5:33 PM

Leaderboard

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Is this your first CTF? Let's begin by tackling the first challenge released on Daily AlpacaHack.

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admin
AlpacaHack 2100
Misc
Welcome🌱
1,824 solves
Upcoming challenges reveal the , , and in advance.
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May 2026

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Writeups

tadanobutubutu

Writeup for Hello Programmer!

tadanobutubutu

ja
Hello Programmer!

1 hour ago

Writeup for I cannot decrypt RSA

author
ja

6 hours ago

tadanobutubutu

Writeup for I cannot decrypt RSA

Daily AlpacaHackに挑戦するつくよみちゃん 05/26/I cannot decrypt RSA/baumroll1234

Rows:

AlpacaForm

Topic: .NETReleased: May 28, 2026

22 solves
Rev
Medium

by

shiragi

shiragi

"This challenge can be solved on Linux alone."

Beginner Hint 1: Challenge Overview (AI-translated)
  • The distributed files are a .NET application written in C# and a flag checker that determines whether the entered string is the correct flag.
  • AlpacaForm.exe is the executable file used to launch the app on Windows. The C# code containing the actual validation logic is in AlpacaForm.dll.
  • .dll stands for Dynamic Link Library. In general, it is a file that contains code or data loaded and used by executable files or other programs.
Beginner Hint 2: Reverse Engineering (AI-translated)
  • AlpacaForm.dll can be decompiled and read in a form close to C# using a .NET decompiler such as ILSpy.
  • For example, try running ilspycmd AlpacaForm.dll to decompile it (Ref).
  • After decompiling it, look for the function that validates the entered string.
alpaca-form.tar.gz

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