angstromCTF 2022 – caniride

Intro We're given a 64-bit ELF which essentially does the following: Ask for a name - this is a 49-character limit string which is stored on the stackList 4 possible "drivers" and ask for a selection (ostensibly an integer between 0-3)Print out the driver name and description (stored in an array of pointers in the…

DiceCTF 2022 – data-eater

A quick note: this method is very much unintended - we knew we were missing something big while working on this challenge, though we didn't realize how much we missed until we saw the author write-up. This was the first CTF that the two of us (fortenforge and I) had done in many months, not…

Midnight Sun CTF 2021 – dbcsig_64434

Github

Midnight Sun CTF 2021 – ocat_024

Github

CSAW Quals 2018 – holywater

This was my favorite crypto challenge from this year's CSAW Quals (and probably my favorite crypto challenge that I've done in a while). On the surface, it's relatively standard: we have a flag encrypted with some cryptosystem (along with a Python implementation of this cryptosystem) and we have to decrypt it. The cryptosystem itself is…

Tokyo Westerns CTF 2018 – load

load was a warmup pwn, though it ended up being on the hard side for a warmup: it had 49 solves compared to 134 for the next easiest warmup (scs7). We spent quite a long time on this challenge (I think ~8 hours in total?), but despite the unexpected difficulty I still had a lot…

Google CTF 2018 – Tape

The description of this challenge is: “We’ve found this priceless, old magnetic tape in our archives. We dumped the contents, but the data is corrupted and we can’t read it. We only have this old tape reader tool, but source code was lost long ago. The program has only 944 bytes, so reversing it should…

Google CTF 2018 – Better Zip

The legacy ZIP crypto is long broken, so we’ve fixed it In this challenge, we are provided with a Python script (better_zip.py) that generates an encrypted zip file from an input file and key, and want to decrypt flag.zip, which was generated with this script. The script has two main parts: a BetterZipCreator class that…

Google CTF 2018 – Feel It

We are given a pcap file, so let’s open it up in Wireshark: As can be seen, the entire pcap consists of USB packets. The overall structure of the file is something like: At the beginning, the host asks a USB device for its descriptors (i.e. configuration information). Then, the host repeatedly sends SET_REPORT requests…

Tokyo Westerns CTF 2017 – Palindromes Pairs (Challenge Phase)

This challenge was a follow-up to an earlier challenge, titled "Palindromes Pairs - Coding Phase". In that earlier warmup ppc challenge, the goal was to write an algorithm to solve the following problem: given up to 1000 strings $latex s_i$, each of length at most 1000, count the number of pairs $latex (i, j)$ such…