Solving the Jane Street Reverse Engineering Challenge

Solving the Jane Street Reverse Engineering Challenge involved working backwards from a GDS file to understand the chip's functionality. The challenge consisted of two parts - a warmup with more information and a main puzzle with less information. The author began poking around in the files, identifying familiar words such as "clk" (clock), "rst" (reset), and "VGND" (Ground Voltage), as well as elements with prefixes like "sky130_fd_sc_hd__".

They utilized the Python library "gdstk" to read and parse the files, which revealed there were 27 elements in the warmup puzzle. The author created a VCD file to simulate the main puzzle, and discovered that it contained ASCII characters, hinting that the circuit had messages embedded within it. Building a circuit simulator using SQLite3 as a driver, parsing the circuit in Python, and creating a harness for testing and visualization proved to be challenging tasks.

The author eventually gave up on their custom software and turned to existing tools, such as the "surfer" circuit simulator and the GDS viewer. By examining annotations and layer information, they were able to roughly identify inputs and outputs, and understood that "sky130" represented a standard for chip design. Leveraging the information from the documentation and SVG labels, the author was able to map specific geometry to the I/O of the circuit elements, ultimately mapping the challenge to a more manageable task.