Author:
SirWardrake

Language:
C/C++

Upload:
3:55 AM 03/04/2024

Download

Platform
Windows

Difficulty:
4.0

Quality:
4.3

Arch:
x86-64

Description

Try to write a keygen

• Comments
• Solutions

nightxyz on 9:22 PM 03/08/2024: Found valid usernames/passwords but couldn't solve algorithm yet.

cnathansmith on 11:14 PM 03/15/2024: @nightxyz try entering a repetitive username like AAABBBCCC and look at what password it converts it to, and you should be able to figure out how to extract the information you need to generate passwords for arbitrary usernames

nightxyz on 12:09 AM 03/16/2024: @cnathansmith Thank you. I have already found the password equivalent of usernames such as "AAAAA" or "aa". Later, I thought about making a table for all the letters, but I gave up because it was a long job and I was struggling with cracking the password of the crackme file named Bobby.

a764934018@outlook.com on 10:57 AM 03/16/2024: reversed its keygen code into C++: https://pastebin.com/4iEaxYm8

cnathansmith on 5:13 PM 03/16/2024: @a764934018@outlook.com Nice! I went the lazy route and just used this as a username: !!""##$$%%&&''(())**++,,--..//00112233445566778899::;;??@@AABBCCDDEEFFGGHHIIJJKKLLMMNNOOPPQQRRSSTTUUVVWWXXYYZZ[[\\]]^^__``aabbccddeeffgghhiijjkkllmmnnooppqqrrssttuuvvwwxxyyzz{{||}}~~ Then split up the password it generates in order to get the substitution values for each character (each input char is doubled up because the substitutions are variable length and it would be impossible to know where each begins and ends in the generated password otherwise)

SirWardrake on 1:05 AM 03/17/2024: @a764934018@outlook.com: Good job, that solution works well! Did you use Ida / Ghidra for this?

a764934018@outlook.com on 1:37 AM 03/17/2024: @cnathansmith what a clever method! learned it. :) I am new to RE and want to learn more so I take my time to reverse it.

a764934018@outlook.com on 1:38 AM 03/17/2024: @SirWardrake thanks. great crackme :) and yes, I used ghidra for this.

1337ReverseEngineer on 10:53 AM 03/17/2024: good crackme but the fact it was UPX packed made the unpacking trivial. if your focus is on keygen maybe dont pack it at all

rrookie on 2:24 PM 03/22/2024: My keygen sticks more to the disassembly. https://pastebin.com/Tr2FaT4A

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