cubk

cubk is a computer science student and a programming enthusiast from PRC

His main interests are Java deobfuscation and reverse engineering. He also has experience in web development and has recently been studying web reverse engineering. Outside of programming, he enjoys writing. On this site he shares technical notes, reverse-engineering write-ups and project experience.

Info

• Based in: Shenyang, Beijing
• Year of birth: 2007
• Languages: Mandarin (native), English
• Programming languages: Java, JavaScript, C/C++, TypeScript
• Email: cubk80@gmail.com

Research

Zelix KlassMaster (2025)

Zelix KlassMaster is the best Java obfuscator on the market, and many companies use it to protect their applications against reverse engineering and tampering. The tool is extremely stable, can handle almost any project, and reliably produces obfuscated code that runs correctly. It offers advanced control flow obfuscation, string encryption, integer constant encryption, method parameter obfuscation and reference obfuscation, along with parameter obfuscation: to decrypt a constant inside any method, you have to trace the entire parameter encryption chain from the start of program execution down to that method.

He and his team manually restored Zelix KlassMaster-obfuscated code back to project source code, without any LLM or agent, and with no loss of functionality.

• Article
• Source code
• Live demo

Arkose Labs CAPTCHA (2026)

Arkose Labs CAPTCHA (FunCaptcha) is a very powerful CAPTCHA system used on pages such as GitHub's sign-up. It has long been updated frequently and presents highly complex, difficult challenges, to the point that even legitimate users often struggle to pass.

He developed a full-protocol solver for Arkose Labs CAPTCHA that uses no headless browser and is written entirely in pure Java 17.

• Article