skills.rest
lNwNl
lNwNlCOMMUNITY
Explore all skills by this author →
GitHub

vm-and-bytecode-reverse

Reverse custom virtual machines by identifying dispatchers and reconstructing their ISA.

2|Updated May 15, 2026
Search Tags:#bytecode#reverse engineering#CTF#disassembler#vm analysis#opcode mapping#maze solving
One-click install
npx skills add https://github.com/lNwNl/Methodos --skill vm-and-bytecode-reverse-lnwnl
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: vm-and-bytecode-reverse
Source: https://github.com/lNwNl/Methodos/tree/main/docker/opencode/skills/vm-and-bytecode-reverse
Command: npx skills add https://github.com/lNwNl/Methodos --skill vm-and-bytecode-reverse-lnwnl

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve?

This Skill helps you reverse custom virtual machines and proprietary bytecode interpreters when a challenge or protected binary hides the real logic behind a dispatcher loop and its own ISA.

Core Features & Use Cases

  • Dispatcher identification: Locate switch/table/indirect-jump or if-chain dispatchers and distinguish stack-, register-, and maze-style VMs.
  • Opcode mapping & ISA reconstruction: Determine opcode values, operand sizes/types, side effects, and build an executable mental model of the VM.
  • Bytecode extraction & disassembly: Extract the bytecode program, then write a custom disassembler to produce readable assembly for downstream analysis.
  • Practical solving workflow: Trace input flow, reverse transformations (XOR/ADD-like checks), and handle maze grids with BFS/DFS when applicable.
  • Protector-oriented tactics: Analyze real-world VM protector patterns (e.g., VMProtect/Themida/Tigress) and decide between tracing, decryption, or symbolic solving approaches.

Quick Start

Use vm-and-bytecode-reverse to reverse a custom VM binary by identifying its dispatcher, mapping opcodes to semantics, extracting the bytecode program, and producing a disassembled listing that reveals the input validation logic.

Frequently Asked Questions about vm-and-bytecode-reverse

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I reverse engineer a custom VM bytecode interpreter?▼

To reverse engineer a custom VM, identify the dispatcher loop, map opcode values to their operational semantics, extract the bytecode, and write a custom disassembler to reveal the validation logic.

What is the best way to analyze a switch dispatcher in a protected binary?▼

Analyzing a switch dispatcher involves locating the indirect jump or table structure to distinguish stack, register, or maze-style VMs, then determining operand types and side effects to reconstruct the proprietary ISA.

How do I solve maze grid navigation checks in CTF bytecode?▼

Solve maze grid navigation in bytecode by tracing input-to-check data flow within the custom disassembler output, then applying pathfinding algorithms like BFS or DFS to find the valid traversal route.

Does this approach work for analyzing nested encrypted bytecode layers?▼

Yes, this approach handles nested and encrypted bytecode layers by tracing dispatcher execution and decrypting transformations, allowing you to reconstruct the ISA and apply symbolic or constraint solving.

How do I map opcode semantics for a proprietary instruction set architecture?▼

Map opcode semantics by tracing dispatcher execution to determine opcode values, operand sizes, and memory side effects, building an executable mental model of the proprietary instruction set architecture.

When should I use symbolic execution instead of tracing for VM protectors?▼

Choose symbolic execution over tracing for VM protectors when the bytecode contains complex nested transformations or encrypted layers, deciding between decryption, tracing, or constraint solving approaches.

Related Skills

Explore More Software Engineering Skills→
Prohao42Prohao42
120

vm-and-bytecode-reverse

Identify VM dispatcher patterns and map opcodes to build a custom disassembler.

Community
Advanced
pluginagentmarketplacepluginagentmarketplace
3

graph-algorithms

Execute DFS, BFS, Dijkstra, and Union-Find on user-provided graphs.

Community
Advanced
lNwNllNwNl
2

code-obfuscation-deobfuscation

Deobfuscate native binaries using emulation and symbolic execution.

Community
Advanced
sayseven7sayseven7
11

vm-and-bytecode-reverse

Reconstruct custom VM opcodes and bytecode execution logic from binaries.

Community
Advanced