Zydak's Very simple but obfuscated crackme

Author:
Zydak

Language:
C/C++

Upload:
2026-08-16 00:45

Download

Platform:
Unix/linux etc.

Difficulty:
3.0

Quality:
4.0

Arch:
x86-64

Downloads:
109

Size:
1.48 MB

Writeups:
0

Comments:
4

Description

A very simple crackme obfuscated with my obfuscator called LeetObfuscator, you can find it on github. There's a single xor of the hardcoded key and compare with user input. Without obfuscation it would take 5 minutes to crack. The solution is to make a keygen, it's not patchable. Flag will be in LEET_FLAG{flag} format.

Labels ?

Anti-debugging Exception-based (SEH/VEH/INT2D) String / data encryption XOR Control-flow obfuscation Spaghetti / junk-branch Exception / interrupt-based Indirect / computed jumps & calls State machine / dispatcher Control-flow flattening (CFF) Anti-disassembly Junk / garbage bytes Opaque predicates Overlapping / misaligned instructions Jump-based desync

Comments (4)
Writeups (0)

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SVz on 2026-08-16 09:14: [Click to reveal]

Zydak on 2026-08-16 09:33: @SVz nice! Would you say it was hard to see through the obfuscation?

SVz on 2026-08-16 13:13: Yeah, clearly impossible via static analysis. A lead using a length-based oracle: by counting executed blocks (qemu-x86_64 -d │ exec,nochain) for inputs between 1 and 40 characters, a massive spike appears at n=7 (+1300 blocks vs the ~30 trend) → password length = │ 7.

Zydak on 2026-08-16 14:00: cool trick, thanks for taking the time to solve this. I'll be posting more of these with each update to the obfuscator, hopefully not as trivial as this one.

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Zydak's Very simple but obfuscated crackme