CrackMe #1 [C#]

Hello guys,

this is my first CrackMe so dont except much. It quite simple to crack since there is no obfuscation involved here. But maybe i could add that later :slight_smile: The Program consists of two parts. The CrackMe1.exe and the License.dll.

Your goals are:

  • to write a keygen (really really easy)
  • to patch the programm so that you can enter anything and it says “License key valid”

Rules:
Dont modify the CrackMe1.exe in any Way! You can decompile to see what it does but dont change anything inside of it.

Have fun!

Downlaod: https://mega.nz/#!2QoTgBSD!h6sdjQDhZAbV1REUychAZ7QVdS5Q67Og4-cM5ceU8BY
Virustotal for the .exe: https://www.virustotal.com/#/file/96979226822e7b88e0c9cd058ed51c5a2dfcdeeb7e8974e09f08bc0446a4a4b4/detection (idk where this detection comes from)

Virustotal for the .dll: https://www.virustotal.com/#/file-analysis/NTEyODBkOTZkMTg5N2I5NGYwNjFiZjViMTlmYTM0MDk6MTUyNTYyNTg3Nw==

6 Likes
Spoiler

Username: GGen
License: D5451FA856A0814F98B800C013E6C92B
All you have to do is calculate MD5 Hash (there are many generators online) from username.
I just started .Net reflector to decompile and was just clicking around to this moment:


Then everything became clear

3 Likes

Hey @GGen!

Congrats on solving this :smiley:

Quick tip: on 0x00sec you can actually also use the [spoiler] something spoilery [/spoiler] format to conceal information. I noticed you found your own creative way to do it - but this is how we normally do it.

:slight_smile:

3 Likes

Cool! I spent 30 secs on flag1 and then spent 10 mins on flag2 but eventually find out that was only a simple patch check

Umm, in one of the goals you said to patch the program, then later you said to not modify anything inside the executable?

You can patch the program without editing the executable :slight_smile: