Category: Rev

Difficulty: Insane

Points: 493 (9 solves)

Challenge Description

Mcvaru skate aka skate homie is trying to put in some practice at skatepark IOR, but scooter kids keep getting in his way and snaking him. Out of anger he yells at one of the kids, but it's 2023, scooter kids have evolved. They now demand some sort of code if you want them to move. Find the flag and help varu skate land a hardflip at the 6 stair.

PS: ./compiler program password

Overview

In this challenge we are given a compiler and file containing some custom assembly code (skatepark.IOR). The compiler takes in said file and a passwords and runs the custom assembly with the password as input.

Looking at the IOR file we can guess what some of the instructions do and how the compiler works in general:

Category: misc

Points: 493 (15 solves)

Challenge Description

I want to check if any of my passwords have been stolen, but I don't want to risk sending them to Have I Been Pwned. I want a stronger guarantee than the k-anonymity that they provide. You can help me by submitting any leaked passwords you may find to a private set intersection protocol.

Usage: ./psi_sender.py password1234 notthepassword fall2021

Solution

In this challenge we are supposed to find all passwords in a private set intersection protocol from this paper. The exact workings of the protocol are not terribly important since we exploit the fact that the polynomials are related.