CTF Challenge: What's going on the FPGA?

7 November 2023

You're designing a solution for one of your customer, and you need their keys in order to connect to their cloud service. However, the customer is very much afraid of hackers. So that, the customer designed a piece of hardware for storing important key that you need. They gave the hardware to the shipment company with the documents needed to use it.

However, shipment company made a mistake and the documents are sent to another country. They told you, it is not possible to delivered it before the next monday. Lucikly, you've recieved the hardware itself.

Since we have to deliver our solution as soon as possible, we want to extract the key inside the hardware. To do that, the first step was investigating the board and extract some information on your our own. This is where the test engineers helped us. They made some block-box testing on the hardware and send us a file which includes their test results which may include the key inside.

Your job is to investigate the file send by the testers and find the key. The key is the flag for this challange and it is formatted as "F{XXXXXXXX}".

Hint #1

You've asked the test engineer about what the heck is this file. They told you that it is a logic simulation file which includes waveforms of the all inputs and outputs of the test scenerio. After that they saw you've no idea what's going on, they send you the automated test file they made to grab these waveforms.

The file link: https://gyokhan.com/content/files/2023/11/BlackBoxBlockTestbench.vhdl

Hint #2

All those steps are for nothing! You haven't found anything. No worries. Still, you can contact to your customer about what does this hardware do. They informed you that this is a FPGA hardware, and they can send you the VHDL file without the flag inside.

Here is the FPGA's VHDL file without the real flag: https://gyokhan.com/content/files/2023/11/BlackBoxBlock.vhdl

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