ZKPOK is a challenge I made while learning Zero Knowledge Proofs on zk-learning.org. I was watching the first lecture video, I came across with the interactive proof for quadratic residues at 20:00. This made me ponder - it should be easy to apply Fiat-Shamir transform to make this non-interactive. Let’s also use MD5 so that it could be vulnerable. Hours later, this challenge appeared without a proper solve script.

This is yet another edition of Google CTF, where I wrote some crypto challenges with my colleagues. I contributed on three challenges this time, namely, Blinders, ZKPOK and IDEA. There are respectively 56, 3 and 4 solves (out of 267 teams scoring non-zero flags) during the contest period.

Blinders is one of the challenges I coauthored, which introduces a protocol for private set membership.

I came across with @intigriti’s XSS challenge this month. This time we are given a love letter storage system which allow us to show our love to our hacking buddies.

TetCTF comes back with their great crypto challenges. I played with @blackb6a and we ended up securing the 🥉 third place. In this blog post, I will walk through adapt, a challenge which required us to make fake proofs in an IAVL tree implementation. There are only three solves during the contest period.

We will finally cover the non-crypto challenges that I wrote for HKCERT CTF 2023. This includes one misc (Hackforces), two pwn (ISA Jump Scare & ISA Jogger) and two reverse (The Flag Game & Loot and Scoot) challenges.