Hello, I’m Hyunsik Jeong a.k.a. RBTree. I mainly write articles related to cryptography, reverse engineering, and other CTF/security-related stuffs here.

## Interpolation Attack

I made one crypto challenge each for CODEGATE CTF 2022 quals and finals. In this article, Iโm gonna explain how the interpolation attack works, and show the way to solve my challenge โHidden Command Serviceโ from the finals. Interpolation Attack Once upon a time, there was a dangerous attack technique called โdifferential cryptanalysisโโฆ Then, two crypto-magicians made a scheme which is provably safe from the differential cryptanalysis, called KN-Cipher. However, it soon turned out that the structure of S-boxes used in those ciphers are vulnerable to a new attack called โinterpolation attackโ, and a variant of KN-Cipher called PURE is broken....

## Cube Attack

I made one crypto challenge each for CODEGATE CTF 2022 quals and finals. In this article, Iโm gonna explain how the cube attack works, and show the way to solve my challenge โHappy S-boxโ from the quals. Cube Attack Consider a multivariate equation over $\text{GF}(2)$, $f(x_1, \dots, x_n)$. There will be multiple monomials in $f$, and what we want to do is to pick one monomial $g = x_{i_1}x_{i_2} \cdots x_{i_k}$ and divide $f$ by $g$....

## ์ ๋ฌธ์ฐ๊ตฌ์์์ ์ํ ํ๋ จ์ ์ค๋น๋ฌผ ๋ฐ ํ

2022๋ 7์ 7์ผ์ ํ๋ จ์์ ์ ์ํด์ 7์ 28์ผ์ ํด์ํ์ต๋๋ค. ๋คํํ๋ ์ข์ ์ฌ๋๋ค๊ณผ ๊ฐ์ ๋ถ๋์์ ์ํํด์ ์ ์ง๋ผ ์ ์์์ต๋๋ค. ์ด ๊ธ์์๋ ๊ฐ์ธ์ ์ผ...

## Posts from the Samsung Software Membership blog

Finally, I copied my posts from the Samsung Software Membership blog. Those are not translated yet. I hope I can finish the translation someday. ๐ข๐ข๐ข Digital Signatures and Nonce Reuse Shellcoding and Bitflip Conjecture Smooth numbers and Factorization On Factoring Given Any Bits Forgery Attack on ElGamal Signatures How to build WebAssembly apps with Rust AntiVirus Oracle Singular Elliptic Curves Anomalous Elliptic Curves SMT Solvers in CTF -...

## SageMath script for AES-GCM challenges

There was an interesting challenge about AES-GCM in LINE CTF 2022, called โlazy STEK.' Iโm not gonna talk about the challenge itself. When I was solving this challenge, I realized that I did not save a script to convert between byte blocks and $\mathbb{F}_{2^{128}}$ elements in SageMath. As it is a bit confusing to understand how the conversion works, I share my script with the solution of lazy STEK here for someone struggling with this problem....