NorthSec 2020 Write-Up: Acrossword Puzzle

Guillaume Ross
6 min readMay 22, 2020


This year, some evil people part of the NorthSec organization gave us a very simple challenge. A crossword.

The crossword was distributed in the form of a PDF with a single page.

The evil crossword puzzle

It consisted mostly of questions about classic cyberpunk novels, and the vertical line 0 was an obvious flag. This write-up explains how to get to the flags, assuming you had no idea what any of these books were.

First Flag

It’s a CTF, so of course, you’re suspicious of the PDF. You look at metadata. Maybe there’s some info about the answers in there?

No, but there’s a flag.

PDF Producer Flag

Seeing that PDF Procuder field with what is clearly a base64 encoded piece of data should give you a little jolt of adrenalin.

Simply copy it to your clipboard and convert it…


Second Flag

We’re done with the “technical” aspect of this CTF cha. We now have 13 questions to answer.

1. Astronomer who wrote a book about a security incident at the Lawrence Berkeley Laboratory

The answer is


2. She is the Razorgirl

There are a few characters referred to as “Razorgirl” in books. By Googling, you’ll probably find that it is either Molly Millions, Trinity, or Motoko Kusanagi. Molly is the “real one” and is also the one that fits within the amount of characters allowed.


3. Cyberpunk novel, and soon to be TV series, which coined the word “meme”

If I have learned anything from high school, it’s that when you don’t know the answer to a question, you should read the rest of the exam.

If you Googled around, you’d find that the answer should be The Selfish Gene.

From Wikipedia:

The word meme is a neologism coined by Richard Dawkins.[11] It originated from Dawkins’s 1976 book The Selfish Gene.

That does not fit. But if you read all the way down, you’ll have noticed that question 13 refers to this one. The name of this book is the name of a drug in the book.

Google for cyberpunk books drug meme and you will quickly find the answer:


4. Answer which took over 7 million years to compute

42. Not worth explaining. Well, I can explain it’s spelled FORTY-TWO, and that is nice because you can now see that the vertical line starts with FLAG-.


5. Real author surname who wrote about a “Three Alarm Lamp Scooter”

We are looking for a real name here.

First, go to Google Books, then, search for Three Alarm Lamp Scooter.

Right away, it is obvious the book we are talking about is Interface.

If we look it up on Wikipedia, we see it was written by: Neal Stephenson and J. Frederick George (a pseudonym of George Jewsbury). Stephenson does not fit, therefore, the answer has to be Jewsbury, the only other real surname of an author of this book.


6. Surname of Canadian-British author who wrote a book on toaster DRM

An easy one, simply Google Toaster DRM Book and you will see the author right away.


7. Sobol’s lesser-known game.

This question was evil, and I thought it was Brett Sobol’s THE RECKONERS. It was not. Whoever got it, please submit it in the comments. I was so sure I had it, I didn’t even get banned trying to brute-force it on askgod.

Update from Monchou’s explanation on NSEC Slack: Turns out, it was completely unrelated to Brett Sobol. I had found out about him and forced myself to find a game that would fit in there. Turns out it’s about the book Daemon, where a character, Matthew Sobol, created The Gate, Over The Rine and The DAEMON. Only one of thise fits.


8. Last name of management which created a hotel AI

I found this one slightly tricky. Hotel AI is depicted in Altered Carbon, which you may have seen on Netflix.

For many reasons, probably including rights to the likeness of the person we are looking for here, that hotel AI in the TV show is based on Edgar Allan Poe, and called Poe, and the hotel is called The Raven.

Googling Hotel AI Cyberpunk Book gives us Altered Carbon as the 2nd result. If you look at the Wikipedia page for it, you will see that the hotel is called Hendrix in the book.

If you dug a bit more in the actual books, you’d find that the Hendrix upgraded itself.


The answer is therefore:


9. Homicidal supercomputer whom Dr. Guess has a special bond with

First, we find the book by Googling Dr Guess Computer. We instantly find that the book is The Computer Connection.

Then, we find the list of Fictional Computers on Wikipedia and look up that book.


10. Company that evolved paranoiac software to say things such as: “Based on the information you have gathered, do you consider it more likely that I am a lurker, or a spoofer? Currently it is more likely that you are a lurker.”

Google is your friend again. Simply look for “Currently it is more likely that you are a lurker”.

You will have found a link to the story, as a PDF or text file. Search for Company in it, and you will soon find a company name…

Lamarck Logic


11. Test to differentiate human and asteroid

I am not sure if this was an honest mistake or meant to throw us off. On the 2nd day of the CTF, asteroid was changed to “android”, and I started to wonder if maybe there was no flag in the crossword puzzle at all. That’s how I found the first flag, actually.

In any case, you had probably guessed it right already, and if not, once you had the correction, simply Googling for test to differentiate humans from android cyberpunk or similar will lead you to Philip K. Dick. The answer is from Do Androids Dream of Electric Sheep? or Blade Runner:


12. Mala’s “Big Sister”

I had no idea what this one was, so I headed to Google Books again. By searching for Cyberpunk novel Mala sister, I quickly found the book For The Win, which happens to be written by Doctorow, answer number 6. I thought that was a good sign.

Once you know what the book is, simply Google for Mala Sister For The Win.



13. Cost of eponymous drug from question 3, after inflation

We have already answered #3, so we know this is about the price of Snow Crash after inflation. No, it’s not some math question.

Snow Crash is easily available. I already had it. You can find it anywhere, and search for Inflation. You will find a few instances of it, but only one that fits.