GTK.

Overview

GTK is a basic Windows x86-64 binary designed as an introductory reversing challenge.
The objective is straightforward: analyze the program logic and recover the correct password.

For this challenge, I will be using IDA Free 9.2.

Initial Recon

Running the binary prompts the user to enter a password in order to unlock the flag.

A quick inspection confirms that this is a 64-bit Windows executable.

Since the binary is small and simple, we proceed directly to static analysis.

Static Analysis

The binary is loaded into IDA for inspection.

From the control flow graph, we can observe:

• A comparison between user input and a predefined value
• A conditional jump (jnz – Jump if Not Zero)

The jnz instruction indicates that if the comparison fails, execution jumps to the failure branch. Otherwise, it proceeds toward the success path.

Decompilation & Logic Analysis

To better understand the logic, we decompile the function using F5 in IDA.

The pseudocode clearly shows the program comparing the user input against a hardcoded value.

Once we identify this value, we can simply provide it as input to satisfy the condition.

Solution

After entering the correct value identified during analysis, the program reveals the flag:

Conclusion

This challenge serves as a simple introduction to:

• Static analysis
• Control flow inspection
• Understanding conditional jumps (jnz)
• Basic decompilation workflow in IDA

Although straightforward, it reinforces the importance of reading program logic rather than blindly testing inputs.