# Reverse Engineering

> Static and dynamic reverse engineering — ELF/PE analysis, custom-VM bytecode, packed binaries, anti-debug bypass, Frida hooking.

- Skill: `transilienceai/reverse-engineering` (Agent Skill, multi-file: 26 files)
- Install (CLI): `npx skillmds@latest add transilienceai/reverse-engineering`
- Raw SKILL.md: https://api.skillmd.com/api/skills/transilienceai/reverse-engineering/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: transilienceai (https://skillmd.com/u/transilienceai)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/transilienceai/reverse-engineering

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# Reverse Engineering

## Scope

Reverse engineering compiled binaries (ELF, PE, Mach-O) and bytecode artifacts to recover algorithms, validate inputs, or build static solvers. Focused on the recurring CTF / malware-analysis pattern of a host binary that loads a "program" file under a custom ISA — recognising the dispatcher loop, mapping opcodes to Python lambdas, and inverting the transformation chain in pure Python without executing the host. Also covers callfuscation (control-flow chunking), MBA (mixed boolean-arithmetic) operator obfuscation, encrypted-handler tricks, and three-layer deobfuscation pipelines.

## When to use

- A binary plus a "program data" file are delivered together and the binary appears to be an interpreter (themed opcode names, dispatcher switch / jump table).
- Disassembly reveals a `while(true){ op = mem[pc++]; switch(op){...}; }` style loop or jump-table indexed by opcode.
- The binary is heavily obfuscated (callfuscation, MBA wrappers, encrypted handlers in `.data` decrypted to RWX at startup).
- You need to recover an algorithm or check function from native code without dynamic execution (anti-debug, wrong arch, no TTY).
- Static-first reverse engineering is preferred (faster, more reliable than emulator chains).

## References

- [reference/custom-vm-bytecode.md](reference/custom-vm-bytecode.md) — recognising and inverting custom stack/register/tape VMs; callfuscation linearization; MBA operator identification; encrypted-handler decryption.