---
id: wiki-2026-0508-code-obfuscation
title: Code Obfuscation
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [Obfuscation, Anti-Reverse Engineering]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [security, reverse-engineering, drm, javascript]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: JavaScript/C++
  framework: obfuscator.io/LLVM-Obfuscator
---

# Code Obfuscation

## 매 한 줄
> **"매 reverse-engineering cost 의 raise — semantic 보존하면서 readability 파괴"**. Crypto 처럼 secrecy 가 아닌 cost-shifting — determined attacker 는 매 결국 풀 수 있음. 매 modern usage: anti-piracy, anti-cheating, license validation, 매 LLM-based deobfuscation 의 등장으로 의미 retreat.

## 매 핵심

### 매 layer
- **Lexical**: rename identifier (`x_a1b2c3`).
- **Control flow**: opaque predicate, control-flow flattening.
- **Data**: string encryption, constant unfolding.
- **Anti-analysis**: anti-debug, VM detection, integrity check.
- **Virtualization**: custom VM bytecode (VMProtect, Themida).

### 매 trade-off
- Performance: 2-10× slowdown (virtualization 시).
- Size: 2-5× binary bloat.
- Stability: false positive 가능 (anti-debug).
- Security: 매 cost-raise 만 — break 시간을 hours → weeks 로.

### 매 응용
1. JavaScript bundle (anti-scraping).
2. Mobile app DRM, license check.
3. Game anti-cheat (e.g., VAC, EAC).
4. Malware (defensive obfuscation).

## 💻 패턴

### String encryption
```javascript
// Before
const KEY = "secret-api-key";

// After
const _0xa1b2 = ['c2VjcmV0', 'LWFwaQ==', 'LWtleQ=='];
const _0xc3d4 = (i) => atob(_0xa1b2[i]);
const KEY = _0xc3d4(0) + _0xc3d4(1) + _0xc3d4(2);
```

### Control-flow flattening
```c
// Before: linear flow
void f() { a(); b(); c(); }

// After: dispatcher loop
void f_obf() {
    int state = 0;
    while (state != -1) {
        switch (state) {
            case 0: a(); state = 7; break;
            case 7: b(); state = 3; break;
            case 3: c(); state = -1; break;
        }
    }
}
```

### Opaque predicate
```cpp
// Always true at runtime, hard to determine statically
auto opaque = [](int x) { return (x*x*x - x) % 3 == 0; }; // always true for any int
if (opaque(rand())) real_logic();
else fake_branch();  // dead but appears live to disassembler
```

### Identifier mangling (terser)
```javascript
// terser config
{
  mangle: {
    toplevel: true,
    properties: { regex: /^_/ }
  },
  compress: { passes: 3, dead_code: true }
}
```

### Anti-debug (browser)
```javascript
setInterval(() => {
    const t = performance.now();
    debugger;  // pauses if devtools open
    if (performance.now() - t > 100) {
        // devtools detected
        location.href = 'about:blank';
    }
}, 1000);
```

### LLVM IR pass (obfuscator-llvm style)
```cpp
struct StringObfPass : PassInfoMixin<StringObfPass> {
    PreservedAnalyses run(Module &M, ModuleAnalysisManager&) {
        for (auto &GV : M.globals()) {
            if (auto *CDA = dyn_cast<ConstantDataArray>(GV.getInitializer())) {
                if (CDA->isString()) xor_encrypt(GV);
            }
        }
        return PreservedAnalyses::none();
    }
};
```

## 매 결정 기준
| 상황 | Approach |
|---|---|
| Web bundle anti-scraping | terser + javascript-obfuscator |
| Native binary (commercial) | VMProtect / Themida |
| Open-source w/ embedded secret | DON'T — use server-side proxy |
| Game anti-cheat | Kernel driver + virtualization |
| Mobile DRM | Hardware-backed (TEE, SEP) — obfuscation 보조 |

**기본값**: Don't obfuscate — secrets belong server-side. Necessary 시 매 layered defense.

## 🔗 Graph
- 응용: [[Malware Analysis]]

## 🤖 LLM 활용
**언제**: Defense-in-depth context, malware analysis 학습, anti-tamper design.
**언제 X**: Hiding actual secrets — broken by definition. 매 server-side 가 답.

## ❌ 안티패턴
- **Security through obscurity (alone)**: 매 always falls.
- **Embedding API key in client**: obfuscation 으로도 매 보호 불가.
- **Custom crypto**: roll-your-own → obfuscation 보다 매 weaker.
- **Performance ignored**: 10× slowdown 으로 UX 망침.
- **No update path**: 매 break 되면 매 fresh release 필요 — automation 필수.

## 🧪 검증 / 중복
- Verified (Collberg taxonomy, obfuscator-llvm, javascript-obfuscator).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — obfuscation taxonomy + JS/LLVM patterns |
