The personal website for Wu "Cousin" Ka Lok (also known as Cosine, usin, …). This website contains blogs and write-ups to CTF challenges that I find interesting. I would also like to share the mathematics behind cryptography, and how the designed may be exploited for attacks. I also made some visualizations of (sometimes seemingly abstract) mathematical concepts.

Recent posts

Coppersmith’s Method (Part I): Introduction

49 minute read ★★★☆☆

The Coppersmith’s method is an application of lattice basis reduction algorithms (like LLL) to find small solutions to polynomials modulo (N). The applicatio...

Basics of Lattice-based Cryptography

55 minute read ★★★☆☆

Lattice is a very important construct for modern day cryptography, especially when we know that in the future, quantum computers will break both ECC and RSA,...

HKCERT CTF 2021 Selected Write-ups

29 minute read ★★☆☆☆

Last Friday to Sunday there was the HKCERT CTF competition 2021 held by HKCERT. I am not allowed to join the competition (for obvious reasons). Nonetheless I...