> For the complete documentation index, see [llms.txt](https://alham-rizvi.gitbook.io/alhamrizvi/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://alham-rizvi.gitbook.io/alhamrizvi/picoctf-writeups/picoctf/reverse-engineering/virtual-machine-0.md). # Virtual Machine 0 Detailed writeup on medium: ### Virtual Machine 0 — PicoCTF Walkthrough (Reverse Engineering) We are given a `.dae` file representing a mechanical system and a large numeric input. The goal is to understand how the system transforms the input and recover the flag. Opening the `.dae` model in a viewer reveals a simple gear mechanism consisting of three gears: a red gear (input), a grey gear (intermediate), and a blue gear (output). By inspecting the model, we identify the number of teeth on the gears: the red gear has 40 teeth and the grey gear has 8 teeth. From basic gear mechanics, the rotation ratio between two meshing gears is determined by the ratio of their teeth. A smaller gear spins faster. So the transformation is: ``` ratio = 40 / 8 = 5 ``` This means for every single rotation of the input (red axle), the output (blue axle) rotates 5 times. So the entire system simplifies to: ``` f(x) = 5x ``` We are given a large input number, so we multiply it by 5 to get the output. *** ### Exploit Script ```python # given input x = 39722847074734820757600524178581224432297292490103995908738058203639164185 # apply transformation result = x * 5 # convert to hex hex_val = hex(result)[2:] # convert to ASCII flag = bytes.fromhex(hex_val).decode() print(flag) ``` *** ### Final Flag ``` picoCTF{g34r5_0f_m0r3_3537e50a} ``` *** ### Summary The challenge looks complex with a 3D model, but the logic reduces to a simple gear ratio. Once the ratio is identified, the rest is just number conversion. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://alham-rizvi.gitbook.io/alhamrizvi/picoctf-writeups/picoctf/reverse-engineering/virtual-machine-0.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.