Welcome ๐Ÿ‘‹

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.

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. ๐Ÿ˜ข๐Ÿ˜ข๐Ÿ˜ข 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 -...

2022-04-26 ยท 1 min ยท RBTree

SageMath script for AES-GCM challenges

There was an interesting challenge about AES-GCM in LINE CTF 2022, called โ€™lazy STEK.' Iโ€™m 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....

2022-03-27 ยท 2 min ยท RBTree

2021 ํšŒ๊ณ 

ํž˜๋“ค์—ˆ๋˜ ํ•ด ๋งํ•  ์ˆ˜๋Š” ์—†๋Š” ํž˜๋“  ์ผ์ด ์ •๋ง ๋งŽ์•˜๋˜ ํ•ด์ธ ๊ฒƒ ๊ฐ™์Šต๋‹ˆ๋‹ค. ํŠนํžˆ 8์›” ๋‹ฌ ์ฏค๋ถ€ํ„ฐ ์—ฐ๋‹ฌ์•„์„œ ๊ดด๋กœ์šด ์ผ์ด ๋งŽ์•˜๋˜ ๊ฒƒ ๊ฐ™์Šต๋‹ˆ๋‹ค. ๊ดด๋กœ์šด ์ผ์ด ๋งŽ์•„์ง€๋‹ˆ ํ‰์†Œ์— ์ข‹์€ ๋ชจ์Šต...

2021-12-31 ยท 2 min ยท RBTree

Attacking a Variant of the RSA Cryptosystem

์„œ๋ก  ์ด๋ฒˆ ๊ธ€์€ ์ €๋ฒˆ ๋‹ฌ์˜ ๊ธ€์— ์ด์–ด์„œ pbctf 2021๋ฅผ ์ถœ์ œํ•˜๋ฉด์„œ ์‚ฌ์šฉํ•œ ๋…ผ๋ฌธ ํ•˜๋‚˜๋ฅผ ๋ฆฌ๋ทฐํ•˜๋ ค๊ณ  ํ•ฉ๋‹ˆ๋‹ค. ์ด ๋…ผ๋ฌธ์€ Yet Another RSA๋ผ๋Š” ๋ฌธ์ œ๋กœ ์ž‘์„ฑํ•˜๊ฒŒ ๋˜์—ˆ์Šต๋‹ˆ๋‹ค. ํ•ด๋‹น ๋…ผ...

2021-11-21 ยท 7 min ยท RBTree

Breaking Combined Multiple Recursive Generators

์„œ๋ก  10์›” ์ค‘์— ์ œ๊ฐ€ ์†ํ•œ CTF ํŒ€ perfect blue์—์„œ pbctf 2021์„ ์ฃผ์ตœํ–ˆ์Šต๋‹ˆ๋‹ค. CTF๋ฅผ ์ค€๋น„ํ•˜๋ฉด์„œ ๋‹ค์–‘ํ•œ ์•”ํ˜ธํ•™ ๋…ผ๋ฌธ๋“ค์„ ์ฝ์–ด๋ณด์•˜๋Š”๋ฐ, ๊ทธ ์ค‘์—์„œ๋„ ์ฐธ๊ณ ํ• ๋งŒํ•œ ํฅ...

2021-10-24 ยท 5 min ยท RBTree