🧑‍🎓 BestSoftware

Category: Reversing

100 points | 160 solves

Challenge Description

Help! I purchased the license for a software called BestSoftware. However, I forgot the license key to it, could you help me?

My name is "seetf" and my email is "seetf@seetf.sg". Thank you!

For beginners:

• https://www.jetbrains.com/decompiler/

Attached files/Instructions

• BestSoftware.exe

Solution

We can use the linked JetBrains decompiler, dotPeek, to decompile C# programs, such as BestSoftware.exe.

Looking at the source code, we can see the license key checker code:

    public static bool CheckLicenseKey(string name, string email, string licenseKey)
    {
      string shA256 = Program.CalculateSHA256(name + "1_l0v3_CSh4rp" + email);
      return licenseKey.Equals(shA256);
    }

A valid license key for the name seetf and email seetf@seetf.sg is the SHA256 of seetf1_l0v3_CSh4rpseetf@seetf.sg.

To calculate the SHA256, we can use online tools such as CyberChef or convertstring.com. This gives us the hash (license key) 28F313A48C1282DF95E07BCEF466D19517587BCAB4F7A78532FA54AC6708444E.

Flag

SEE{28F313A48C1282DF95E07BCEF466D19517587BCAB4F7A78532FA54AC6708444E}