Solving the Jane Street Reverse Engineering Challenge

235 pointsposted 5 hours ago
by anitil

59 Comments

mdritch

21 minutes ago

I love z3. I used it for the first time for Jane Street's puzzle last year involving a hashing alg disguised as a neural network. I use a lot of MCMC at work and I have made a few small investigations into MCMC model formal verification via z3, but nothing real yet. This has inspired me to pick that back up.

ctippett

3 hours ago

> I ended up using a tool called ‘z3’. It’s kind of magical? Every time it finds a solution I get a surge of joy.

This resonates so much. I had a similar feeling after going to my very first operations research lecture. Solving seemingly incomprehensibly complex problems by framing them as a bunch of simple constraints and getting a solution seemed like such magic.

xvilka

4 hours ago

To help with such tasks for real chips (given the good quality images) there is Degate[1][2] open source software.

[1] https://www.degate.org/

[2] https://github.com/DegateCommunity/Degate

flaghacker

4 hours ago

Degate is even a bit overkill, it is meant for when you only have images of the physical chip. This challenge has the full GDS files, which are the files that are sent to the fab for manufacturing. They still contain information about all of the separate layers. In this case they even contained the stdcell names, making even full transistor and logic function extraction unnecessary.

piker

5 hours ago

> Well I don’t really know what to work on next

Let me help you: work on figuring out how to spend the millions of dollars every year Jane Street will pay you to clock in. I've heard private aviation is expensive, for example. :)

bko

5 hours ago

A lot of places claim they want to hire extremely smart autists, and some do. But these types of employees are incredibly hard to manage. Imagine herding cats. So if you don't invest a lot of effort in building an environment to let this person cook, go down the right rabbit holes and not rub others the wrong way, a person like this is a huge liability to the org.

vovavili

4 hours ago

A lot of companies who claim to want highly intelligent and autonomous engineers by revealed preference actually want glorified slightly above average ticket pushers.

At least by the looks of it, Jane Street appears to be an odd one to genuinely value competence.

bluGill

3 hours ago

There are a lot of incredibly smart non-autists. Or maybe slightly autistic, but enough awareness of the real world that they can be managed.

Emma_Goldman

3 hours ago

The strong affinity between autism and intelligence seems strongest in technical fields, and engineering and computer science in particular. Autism does not seem to be over-represented to anywhere near the same degree in many other domains that are full of intelligent people.

skinfaxi

an hour ago

Is this just from your direct experience or do you have data to back that up? Are you talking about credentialed engineering like mechanical or civil engineering or just software developers?

bob1029

2 hours ago

Good mentorship can make all the difference in the universe.

folkrav

3 hours ago

Please, explain how you determined this person was an "extremely smart autist".

anitil

3 hours ago

I took it as a compliment!

walrus01

5 hours ago

Google says "Jane Street has global office locations in New York, London, Hong Kong, Singapore, Amsterdam, and Chicago" so if you're really at a loss where to spend your money, I would recommend searching for yacht dealerships in those cities. I'm sure it won't be a problem anymore.

aavshr

2 hours ago

There's a typo on your link to the two stars image.

It should be `/img/two-stars.png` instead it's right now `/img/two-starts.pgn`.

For those interested in the image itself: https://jestoph.com/img/two-stars.png

hosel

2 hours ago

oh boy here we go again

swiftcoder

4 hours ago

I'm not sure I've ever seen such a vicious case of NIH-syndrome. Regardless, congrats on the solve!

bluGill

4 hours ago

Since this was for fun, and the goal was learning at least as much as solving the problem that is just fine. More people should get NIH for those purposes.

Now if he is presenting his tools as a good way to solve this problem, something you should use, or any such - that would be a bad thing. Good tools for this are complex and need to be done as part of a large team. If good tools that others should use is the goal then he should join some other group making those tools. I'm sure there is an existing open source project (maybe KiCAD - I'm not in this space so that is the only name I can come up with but maybe their goals are different?) that does this and would welcome more help.

_false

4 hours ago

I first thought you were teasing Jane Street instead of OP. Maybe shows that OP is a good culture fit for Jane Street :)

AlDante2

3 hours ago

Hi Chris,

just for info: https://en.wikipedia.org/wiki/GDSII will tell you about the GDS format. It apparently stands for Graphic Data System II (originally developed by Calma in the late 1970s).

anitil

3 hours ago

No spoilers! But thanks I did find out after I published, I just thought it was funnier not to know while I was working on it

flaghacker

5 hours ago

Congrats on solving the challenge!

I also briefly wrote about my approach here, with less pictures but going into slightly more detail about how to convert circuits to z3 equations: https://gist.github.com/KarelPeeters/dba417c2690cf0505ac9079...

anitil

4 hours ago

That's really interesting that you actually used z3 to extract the output from the circuit! It hadn't occurred to me that it would be possible to do that. I suppose I got a little fixated on my approach of running a verilog simulation, and I only used z3 to solve one part (though the hardest part I think). How did you get a $DAYJOB involving formal verification?

flaghacker

4 hours ago

Yeah I briefly considered switching to a simulator to get the final output, but then luckily realized the Z3 setup I had was already acting as a super-powered simulator anyway!

I'm not actually using formal verification at $DAYJOB, there we're using MILP solvers (which are closely related to SAT solvers) as part of the compilation flow when scheduling operations onto hardware accelerators.

I have been interested in formal verification for hardware for a while, but so far haven't found an opportunity to apply it. There are some great resources online though: the ZipCpu blog at https://zipcpu.com/formal/formal.html and SymbiYosys website at https://symbiyosys.readthedocs.io/en/latest/. I hindsight I could probably have used SymbiYosys instead of Z3, it would have saved me from having to walk the graph and map the gates to equations myself.

anitil

5 hours ago

Hi HN, I recently solved the Jane Street reverse engineering challenge [0], and I wrote a blog post on how I reached the answer.

It's a moderately technical and (hopefully) entertaining run through of the process. I hope you enjoy reading it as much as I enjoyed doing the challenge (though, as you'll read, it was also quite a frustrating process). My github is on the post if you were interested in seeing a bit more in detail what my solution looked like, though I intend to write some follow up posts that are a bit more in the weeds of the solution. And frankly, the code I used is pretty ugly but it got the job done.

This is my first blog post, so if you have any feedback please let me know. All the writing, all the code was done by me, by hand, in vim.

[0] https://blog.janestreet.com/can-you-reverse-engineer-an-asic...

__atx__

5 hours ago

> It turns out that this ‘sky130’ thing is like a … standard? Or something for making chips.

Very cool seeing someone completely naive going into this :)

If you want to read more about a bit more... cheaty way to do this, I have written about using formal verification machinery to straight up force the solution out of the netlist here: https://atx.name/electronics/asic-re/ . Could be a bit of an infohazard, but I think journey is the goal and yours was certainly more educational :)

anitil

4 hours ago

I'll definitely be reading this thankyou! I think this would have been a much better way to approach it, it's a bit of a joke in the piece that I always do things the hard way, but it's a genuine mystery to me why I operate this way.

I should add I have an EE degree (but have never worked as an EE), so even though I don't know industry standards like this sky130 thing, it's not completely foreign to me.

vzcx

4 hours ago

Nice solution and good easter egg find!

NamTaf

5 hours ago

I really enjoyed the writing, cheers. And yes, you may have done it the hard way, but you probably learnt 10x more by doing that.

As for what to do next, I used to spend way too much of my late-2000s time on puzzle hunts (particularly the Melbourne Uni one [1]) and this tickled the same part of my brain. Unfortunately they're no longer a thing, but it definitely sounds like you'd enjoy something similar.

[1]: https://www.puzzles.wiki/wiki/MUMS_Puzzle_Hunt

vzcx

5 hours ago

Incredible amount of determination, but you really did make it hard for yourself!

You can install librelane to get the whole open silicon tool suite and the sky130 PDK. Circuit extraction can be done with magic. Going from a spice netlist to verilog netlist is pretty mechanical and not a hard transform to write. You almost immediately have something that can be simulated and a good baseline for further reversing.

__atx__

4 hours ago

> Circuit extraction can be done with magic.

So that was the missing part for me! I did it from scratch (with custom Python script with gdstk and shapely) (the GDS file does have the cells annotated, so not a big problem but still). I was thinking about scripting the "trace net" tool in klayout but decided that's going to probably bring its own can of worms...

vzcx

4 hours ago

You can give the cell instances a stable name by setting GDS property 98, which I learned about from my reconnaissance of the puzzle author's github and sky130 visualization tool. This way I was able to spot check a pass over the netlist that broke up the regions into a hierarchical design.

I'd like to do a full writeup but haven't had the time.

anitil

4 hours ago

> Incredible amount of determination

That's very kind of you. At some point I had put so much of myself in to it that I was in too deep and the only was out was to keep digging.

I'll take a look at librelane thanks!

thisisauserid

37 minutes ago

I know nothing about z3 but it's from Microsoft. Would Google's OR-Tools component CP-SAT also be useful for something like this?

nostrebored

2 minutes ago

z3 is also just so thoroughly optimized that even if your formulation of the constraints is inefficient it is faster. it is a great library that lets you solve pretty complicated DP problems with a few dozen lines of code.

myng111

30 minutes ago

Z3 is an SMT solver, not a SAT solver. You'd probably be looking for something more like Yices, Bitwuzla, cvc5, etc.

amelius

4 hours ago

If there's a "two stars" solution, then maybe there is also a "three stars" solution?

skr3178

an hour ago

Solving the puzzle with the assistance of a lower capability LLM model (even though I had access to more) turned out to be fun and good learning experience.

anon-3988

5 hours ago

I have used Codex (Sol 5.6 or whatever) to solve this problem. It turns the problem into Z3, then iteratively work through the problems until it figured out the solution.

Personally, I did not learn that much from that experience. So I am glad that there's other people working on it as well. I am mostly interested in the techniques used to solve this.

seritools

4 hours ago

> Personally, I did not learn that much from that experience.

What did you expect?

anon-3988

34 minutes ago

I understand the sentiment, but in a world where these kinds of problems (And problems at work) that can trivially be solved by LLMs; what kind of value can I provide?

That itself is a learning experience. What is even the point of technical interview questions or take home questions? This means that I am now open to hiring completely non-technical person, as long as they have a good personality and management skills more than a competent developer.

gnyman

4 hours ago

The fact that agents can solve these is telling and the Infosec Capture The Flag community is trying to figure out how to approach.

I recently solved a (in)famously hard challenge (disobey conference hacker ticket) more or less by accident. I say by accident because I have always ignored this challenges as they generally require a lot of patience and motivation to solve. Some years they haven't been solved at all. This year I had a GPT sub with some unused quota so I thought let's see how far it gets.

And it crunched through the whole thing in an evening and morning (occasional poking from me to keep going and steer it right).

Like anon, I learned nothing except that the agents have become really good at solving puzzles. Last time I had thrown a puzzle on them was Advent of code, with GPT3 I think and it struggled so much I gave up my experiment on day 7 or something.

yuye

3 hours ago

>I have used Codex (Sol 5.6 or whatever) to solve this problem.

>Personally, I did not learn that much from that experience

Fire is hot, water is wet, etc

emptyheaded

39 minutes ago

reading the post felt like going down an authentic manic rabbit hole, thanks for sharing your artisanal words @anitil

motoxpro

3 hours ago

So cool to see someone who loves challenges. Congrats!

charcircuit

5 hours ago

I wonder how far a LLM could get with this. It will be cool when we get to the point where you can decap a chip, take a picture, and then an LLM can create an emulator for that chip.

anitil

4 hours ago

I'd say they could solve it much faster than I could. Some of the other commenters are mentioning tools that would have made this so much easier, and I'd assume an LLM would know to use them

vzcx

5 hours ago

This would need good image recognition, but maybe not so far out of the realm of possibility.

These GDS design files have a lot more structure to them.

gyanchawdhary

5 hours ago

curious what the actual use case for a challenge like this is from Jane Streets side .. guess the obvious one is trading even closer to the wire .. being able to reverse engineer .. inspect circuits to uncover flaws or optimisations that shave latency or improve determinism in the trading stack .. but I wonder if there are other less obvious applications ..

bux93

4 hours ago

Probably this is just an unfamiliar domain for most non-hardware folks, so it's a nice challenge that might introduce Jane Street to some people they might want to interview for non-hardware roles.

But, they do have a hardware division, and Jane Street has a podcast that talks about some of the things they do https://signalsandthreads.com/?tag=hardware

gyanchawdhary

4 hours ago

wow thanks for sharing, will check it out