Java Bytecode Obfuscator

A powerful and flexible Java bytecode obfuscator built with ASM that provides comprehensive obfuscation capabilities while maintaining fine-grained control over what gets obfuscated.

✨ Features

🔧 Core Obfuscation

Class Renaming - Rename classes to obscure names while preserving functionality
Method Renaming - Obfuscate method names with intelligent handling of constructors, synthetic methods, and inheritance
Field Renaming - Rename fields while maintaining proper access relationships
Reference Updating - Automatically updates all references to renamed elements throughout the codebase
Inheritance-Aware Renaming - Properly handles interface implementations and method overrides
Multiple Naming Modes - Choose from sequential, alphabetic, random short/long, or single character naming schemes

🎯 Advanced Configuration

Obfuscation Levels - Pre-defined security levels (MINIMAL, BASIC, AGGRESSIVE, EXTREME, CUSTOM)
Keep Rules System - Sophisticated rules for preserving specific classes, methods, and fields
Pattern Matching - Use regex patterns to define keep rules for multiple elements at once
Package Filtering - Include/exclude specific packages with fine-grained control
Granular Control - Specify exactly what to keep at the class, method, and field level
Configuration Files - Enhanced JSON-based configuration with nested structure and presets
Configuration Validation - Comprehensive validation with detailed warnings and error reporting
Command Line Interface - Full-featured CLI with extensive options

🔄 Extensible Architecture

Transformer Pipeline - Modular transformer system with priority-based execution
Abstract Base Classes - Easy to extend with custom obfuscation techniques
Plugin System - Add new transformers without modifying core code
Context Sharing - Transformers can share data and coordinate operations

📊 Enhanced Logging & Analysis

Rich Console Output - Beautiful logging with emojis and color coding
Timestamped Logs - All operations are timestamped for debugging
Progress Tracking - Visual progress indicators and statistics
Mapping Generation - Generate detailed mappings of original to obfuscated names
Obfuscation Resistance Scoring - Comprehensive analysis of obfuscation strength with recommendations
Verbose Mode - Detailed logging of all transformations performed
Validation System - Comprehensive validation with warnings and error detection
Performance Monitoring - Execution statistics and optimization recommendations

🛠️ Smart Handling

Method References - Properly handles Java 8+ method references (::) in lambda expressions
Synthetic Methods - Intelligently handles compiler-generated synthetic methods
Bridge Methods - Correct handling of bridge methods in inheritance hierarchies
Entry Point Protection - Automatic preservation of main methods and constructors
JAR Structure - Preserves non-class files (resources, manifests, etc.)
Multi-threading - Configurable parallel processing for improved performance
Backup System - Automatic backup creation with configurable directory
String Compression - Advanced string obfuscation and compression techniques
Code Optimization - Built-in bytecode optimization during obfuscation

🚀 Quick Start

Installation

Download the latest release or build from source:

git clone https://github.com/cvs0/java-bytecode-obfuscator.git
cd java-bytecode-obfuscator
./gradlew build

Basic Usage

# Simple obfuscation with all features enabled
java -jar java-bytecode-obfuscator-1.0-SNAPSHOT.jar input.jar output.jar \
  --rename-classes --rename-methods --rename-fields --rename-local-variables \
  \
  --obfuscate-conditions --compress-strings --compress-strings

# Maximum security with anti-debugging and resistance scoring
java -jar java-bytecode-obfuscator-1.0-SNAPSHOT.jar input.jar output.jar \
  --rename-classes --rename-methods --rename-fields --rename-local-variables \
  --obfuscate-conditions --compress-strings --compress-strings --anti-debugging \
  \
  --debugger-action EXIT_WITH_ERROR --generate-score --naming-mode RANDOM_LONG

# With main class protection
java -jar java-bytecode-obfuscator-1.0-SNAPSHOT.jar input.jar output.jar \
  -m com.example.Main --keep-main-class --keep-entry-points \
  --rename-classes --rename-methods --rename-fields --rename-local-variables \
  \
  --obfuscate-conditions --compress-strings

# Generate mappings and resistance score
java -jar java-bytecode-obfuscator-1.0-SNAPSHOT.jar input.jar output.jar \
  --mappings mappings.txt --generate-score --verbose \
  --rename-classes --rename-methods --rename-fields --rename-local-variables \
  \
  --obfuscate-conditions --compress-strings --compress-strings

# Use different naming modes
java -jar java-bytecode-obfuscator-1.0-SNAPSHOT.jar input.jar output.jar \
  --naming-mode RANDOM_SHORT --rename-classes --rename-methods --rename-fields \
  \
  --obfuscate-conditions --compress-strings --compress-strings

java -jar java-bytecode-obfuscator-1.0-SNAPSHOT.jar input.jar output.jar \
  --naming-mode SEQUENTIAL_ALPHA --verbose \
  --rename-classes --rename-methods --rename-fields --rename-local-variables \
  \
  --obfuscate-conditions --compress-strings --compress-strings

Enhanced Configuration File

Create a comprehensive JSON configuration file:

{
  "obfuscationLevel": "AGGRESSIVE",
  "mainClass": "com/example/MyApp",
  
  "obfuscation": {
    "renameClasses": true,
    "renameFields": true,
    "renameMethods": true,
    "renameLocalVariables": true,
    "obfuscateConditions": true,
    "compressStrings": true,
    "shuffleMembers": true,
    "optimizeCode": true
  },
  
  "naming": {
    "namingMode": "RANDOM_SHORT"
  },
  
  "security": {
    "antiDebugging": true,
    "debuggerAction": "CORRUPT_EXECUTION"
  },
  
  "packages": {
    "includePackages": ["com/example/core", "com/example/business"],
    "excludePackages": ["com/example/test", "com/example/debug"]
  },
  
  "keepRules": {
    "keepMainClass": true,
    "keepStandardEntryPoints": true,
    "keepClasses": ["com/example/api/PublicAPI"],
    "keepClassPatterns": [".*Controller", ".*Exception"],
    "keepMethods": {
      "com/example/api/PublicAPI": ["publicMethod"]
    },
    "keepMethodPatterns": {
      ".*Controller": ["handle.*", "process.*"]
    }
  },
  
  "debugging": {
    "preserveLineNumbers": false,
    "preserveLocalVariableNames": false,
    "verbose": false,
    "generateScore": true
  },
  
  "performance": {
    "maxThreads": 4,
    "sequentialTransformers": false
  },
  
  "backup": {
    "enableBackup": true,
    "backupDir": "./backups"
  },
  
  "customSettings": {
    "stringEncryptionKey": "myCustomKey123",
    "customTransformerEnabled": true
  }
}

Programmatic Usage

import net.cvs0.Obfuscator;
import net.cvs0.config.ObfuscationConfig;

ObfuscationConfig config = new ObfuscationConfig.Builder()
    .mainClass("com/example/Application")
    .renameClasses(true)
    .renameFields(true)
    .renameMethods(true)
    .renameLocalVariables(true)
    .obfuscateConditions(true)
    .compressStrings(true)
    .compressStrings(true)
    .namingMode(NamingMode.RANDOM_SHORT)
    .verbose(true)
    
    // Keep specific classes
    .keepClass("com/example/api/PublicAPI")
    .keepClassPattern("com/example/config/.*")
    
    // Keep specific methods
    .keepClassMethod("com/example/Service", "publicMethod")
    .keepClassMethodPattern(".*Controller", "handle.*")
    .keepAllMethodsForClass("com/example/PublicInterface")
    
    // Keep specific fields
    .keepClassField("com/example/Constants", "VERSION")
    .keepClassFieldPattern(".*Entity", "id")
    .keepAllFieldsForClass("com/example/Config")
    
    // Convenience methods
    .keepMainClass()
    .keepStandardEntryPoints()
    .build();

Obfuscator obfuscator = new Obfuscator();
obfuscator.obfuscate(inputJar, outputJar, config, mappingsFile);

🎚️ Obfuscation Levels

The obfuscator provides pre-defined security levels that automatically configure optimal settings for different use cases:

Available Levels

Level	Description	Use Case	Settings
MINIMAL	Basic protection with minimal impact	Development, debugging	Classes only, sequential naming
BASIC	Standard obfuscation for most applications	Production applications	Classes, fields, methods
AGGRESSIVE	Heavy obfuscation with advanced techniques	Sensitive applications	All features, anti-debugging, shuffling
EXTREME	Maximum security with performance trade-offs	High-security applications	All features, maximum settings
CUSTOM	User-defined configuration	Specific requirements	Manual configuration

Quick Level Selection

# Use predefined levels
java -jar obfuscator.jar input.jar output.jar --level AGGRESSIVE

# Override specific settings
java -jar obfuscator.jar input.jar output.jar --level BASIC --anti-debugging

Programmatic Usage

// Quick level selection
ObfuscationConfig config = ConfigPresets.createPresetForLevel(ObfuscationLevel.AGGRESSIVE)
    .mainClass("com/example/Main")
    .keepMainClass()
    .build();

// Pre-built presets
ObfuscationConfig prodConfig = ConfigPresets.createProductionObfuscation()
    .mainClass("com/example/Main")
    .build();

ObfuscationConfig devConfig = ConfigPresets.createDevelopmentObfuscation()
    .mainClass("com/example/Main")
    .build();

ObfuscationConfig secureConfig = ConfigPresets.createSecureObfuscation()
    .mainClass("com/example/Main")
    .build();

Level Details

MINIMAL Level

Class renaming only
Sequential naming with prefix
No anti-debugging
Preserves debugging information
Fast processing

BASIC Level (Default)

Class, field, and method renaming
Sequential alphabetic naming
Basic keep rules
Balanced security and performance

AGGRESSIVE Level

All renaming features
Local variable obfuscation
Condition obfuscation
Anti-debugging protection
Member shuffling
Random short naming

EXTREME Level

Maximum obfuscation settings
String compression
Code optimization
Advanced anti-debugging
Random long naming
All security features

Naming Modes

The obfuscator supports multiple naming modes to generate obfuscated names:

Available Modes

Mode	Description	Example Output
`SEQUENTIAL_PREFIX`	Sequential with prefix (default)	`a1`, `a2`, `a3`, `m1`, `m2`, `f1`, `f2`
`SEQUENTIAL_ALPHA`	Sequential alphabetic	`a`, `b`, `c`, `aa`, `ab`, `ac`
`RANDOM_SHORT`	Random short names (4 characters)	`abcd`, `xyzk`, `mnop`, `qrst`
`RANDOM_LONG`	Random long names (8-16 characters)	`abcdefgh`, `xyzklmnopqrs`
`SINGLE_CHAR`	Single character names	`a`, `b`, `c`, then falls back to `a1`, `a2`

Usage Examples

# Use random short names for maximum obfuscation
java -jar obfuscator.jar input.jar output.jar --naming-mode RANDOM_SHORT

# Use single character names for minimal size
java -jar obfuscator.jar input.jar output.jar --naming-mode SINGLE_CHAR

# Use alphabetic sequence for readability in testing
java -jar obfuscator.jar input.jar output.jar --naming-mode SEQUENTIAL_ALPHA

Configuration File

{
  "namingMode": "RANDOM_SHORT",
  "renameClasses": true,
  "renameFields": true,
  "renameMethods": true
}

Programmatic Usage

import net.cvs0.config.NamingMode;

ObfuscationConfig config = new ObfuscationConfig.Builder()
    .namingMode(NamingMode.RANDOM_LONG)
    .renameClasses(true)
    .renameFields(true)
    .renameMethods(true)
    .build();

Condition Obfuscation

Condition obfuscation transforms simple boolean constants (true and false) into mathematically equivalent complex expressions that make the code harder to understand and analyze.

How It Works

The transformer replaces simple boolean constants with arithmetic expressions that evaluate to the same value:

Original Code:

if (someFlag == true) {
    doSomething();
}
boolean result = false;

Obfuscated Code:

// true becomes: 2 - 1
if (someFlag == (2 - 1)) {
    doSomething();
}
// false becomes: 1 - 1  
boolean result = (1 - 1);

Features

Safe Transformation - Only transforms constants that are likely to be boolean conditions (10% probability to avoid breaking non-boolean integer usage)
Multiple Strategies - Uses various mathematical expressions to avoid patterns
Stackmap-Safe - Generates bytecode that passes JVM verification
Conservative Approach - Only targets simple constant loading to maintain program correctness

Usage

# Enable condition obfuscation via CLI
java -jar obfuscator.jar input.jar output.jar --obfuscate-conditions

# Combined with other obfuscation techniques
java -jar obfuscator.jar input.jar output.jar \
  --rename-classes --rename-methods --rename-fields \
  --obfuscate-conditions --compress-strings --compress-strings --verbose

Configuration

{
  "renameClasses": true,
  "renameFields": true,
  "renameMethods": true,
  "obfuscateConditions": true,
  "compressStrings": true,
  "compressStrings": true,
  "verbose": true
}

Programmatic Usage

ObfuscationConfig config = new ObfuscationConfig.Builder()
    .renameClasses(true)
    .renameFields(true)
    .renameMethods(true)
    .obfuscateConditions(true)
    .compressStrings(true)
    .compressStrings(true)
    .build();

Examples

Before Obfuscation:

public boolean isEnabled() {
    return true;
}

public void process() {
    if (false) {
        handleError();
    }
}

After Obfuscation:

public boolean a() {
    return 3 - 2;  // Evaluates to 1 (true)
}

public void b() {
    if (5 - 5) {   // Evaluates to 0 (false)
        c();
    }
}

## 🗜️ String Compression

String compression transforms string literals into compressed, base64-encoded data that is decompressed at runtime. This reduces JAR size and makes string analysis more difficult.

### How It Works

The transformer identifies string literals and compresses them using the Deflate algorithm, then encodes them with Base64. At runtime, the compressed strings are decompressed transparently.

**Original Code:**
```java
public class Example {
    public static void main(String[] args) {
        String message = "This is a very long string that contains a lot of repetitive text and should be compressed effectively using the deflate algorithm for better obfuscation."; (transforms boolean constants)
        System.out.println("Application started with message: " + message);
    }
}

Obfuscated Code:

public class a1 {
    public static void main(String[] args) {
        String a = new String(new java.util.zip.Inflater().inflate(java.util.Base64.getDecoder().decode("eJwLycxNzStJzSvJTFHwSM3JzM+Lz8nPS1WwMjQwMDK1UjA0NDEwMLRSULA0NDQwsDK0MjSyMjKzMjKzMjKzMjK...")), 0, 147, java.nio.charset.StandardCharsets.UTF_8);
        System.out.println("Application started with message: " + a);
    }
}

Features

Intelligent String Selection - Only compresses strings that benefit from compression (length > 10 characters)
Special String Detection - Avoids compressing URLs, configuration strings, class names, and other special patterns
Compression Efficiency - Only applies compression if the result is actually smaller
Configurable Probability - Randomly compresses strings to avoid predictable patterns (70% chance by default)
Runtime Transparent - Decompression happens automatically at runtime
Keep Rules Aware - Respects keep rules and doesn't compress strings in preserved classes

Usage

# Enable string compression via CLI
java -jar obfuscator.jar input.jar output.jar --compress-strings

# Combined with other obfuscation techniques
java -jar obfuscator.jar input.jar output.jar \
  --rename-classes --rename-methods --rename-fields \
  --compress-strings --obfuscate-conditions --verbose

Configuration File

{
  "obfuscation": {
    "renameClasses": true,
    "renameFields": true,
    "renameMethods": true,
    "compressStrings": true
  },
  "debugging": {
    "verbose": true
  }
}

Programmatic Usage

ObfuscationConfig config = new ObfuscationConfig.Builder()
    .renameClasses(true)
    .renameFields(true)
    .renameMethods(true)
    .compressStrings(true)
    .verbose(true)
    .build();

Obfuscator obfuscator = new Obfuscator();
obfuscator.obfuscate(inputJar, outputJar, config, mappingsFile);

String Selection Criteria

The transformer automatically determines which strings to compress based on:

Criteria	Description	Example
Minimum Length	Strings must be at least 10 characters	`"Short"` → Not compressed
Special Patterns	Avoids URLs, config strings, file extensions	`"https://example.com"` → Not compressed
Compression Efficiency	Only compresses if result is smaller	`"aaaaaaaaaa"` → Compressed
Class Keep Rules	Respects keep rules for classes	Kept classes → Strings not compressed
Random Selection	70% probability to avoid patterns	Random selection to prevent analysis

Benefits

Size Reduction - Compresses repetitive or long strings effectively
Content Obfuscation - Makes string analysis much more difficult
Runtime Performance - Minimal impact on application startup
Reverse Engineering Protection - Strings are not visible in decompiled code
Pattern Breaking - Random compression prevents pattern-based analysis

Performance Impact

Compression Time - Adds minimal time during obfuscation
Runtime Overhead - Small one-time decompression cost per string
Memory Usage - Slightly higher memory usage during decompression
JAR Size - Usually reduces overall JAR size for applications with many long strings

Best Practices

Combine with Other Features - Use alongside renaming and condition obfuscation
Test Performance - Profile your application after string compression
Verify Functionality - Ensure compressed strings work correctly in your use case
Monitor JAR Size - Check if compression actually reduces your JAR size

Examples

Long Strings (Compressed):

Error messages and user notifications
SQL queries and database scripts
Configuration templates
Help text and documentation strings

Short/Special Strings (Not Compressed):

Class names and package names
URLs and file paths
Single words and short constants
Format strings and patterns

🔧 Method Inlining

Method inlining replaces method calls with the actual method body, reducing call overhead and making the code harder to analyze by eliminating method boundaries.

How It Works

The transformer identifies simple methods that are good candidates for inlining and replaces calls to these methods with their actual implementation.

Original Code:

public class Calculator {
    public int add(int a, int b) {
        return a + b;
    }
    
    public int calculate() {
        return add(5, 3);  // Method call
    }
}

Obfuscated Code:

public class a1 {
    public int a1(int a, int b) {
        return a + b;  // Method still exists but may not be called
    }
    
    public int a2() {
        return 5 + 3;  // Method call inlined
    }
}

Features

Smart Method Selection - Only inlines simple methods without complex control flow
Safety Checks - Avoids inlining methods with field access or complex operations
Conservative Approach - Prevents inlining that could break functionality
Stack-Safe - Generates proper bytecode that passes JVM verification
Selective Inlining - Only processes methods that benefit from inlining

Usage

# Enable method inlining via CLI
java -jar obfuscator.jar input.jar output.jar --inline-simple-methods

# Combined with other obfuscation techniques
java -jar obfuscator.jar input.jar output.jar \
  --rename-classes --rename-methods --inline-simple-methods \
  --obfuscate-conditions --verbose

Configuration File

{
  "obfuscation": {
    "renameClasses": true,
    "renameMethods": true,
    "inlineSimpleMethods": true
  }
}

Inlining Criteria

Methods are considered for inlining if they:

Are short (< 5 instructions)
Don't access fields
Don't contain loops or branches
Don't throw exceptions
Are not constructors or static initializers

🎭 Fake Interface Flooding

Fake interface flooding generates synthetic interfaces and makes classes implement them, creating false inheritance relationships that confuse reverse engineering tools and static analysis.

How It Works

The transformer creates fake interfaces with random methods and makes target classes implement these interfaces, adding noise to the class hierarchy without affecting functionality.

Original Code:

public class DataProcessor {
    public void process(String data) {
        System.out.println("Processing: " + data);
    }
}

Obfuscated Code:

// Generated fake interfaces
interface a1 {
    void m1();
    int m2(String s);
}

interface a2 {
    boolean m3();
}

public class a3 implements a1, a2 {
    public void process(String data) {  // Original method
        System.out.println("Processing: " + data);
    }
    
    // Fake implementations that never execute
    public void m1() { throw new UnsupportedOperationException(); }
    public int m2(String s) { throw new UnsupportedOperationException(); }
    public boolean m3() { throw new UnsupportedOperationException(); }
}

Features

Dynamic Interface Generation - Creates unique interfaces for each obfuscation run
Configurable Quantity - Control how many fake interfaces are added per class
Method Variety - Generates diverse method signatures with different return types
Exception Throwing - Fake methods throw exceptions to prevent accidental execution
Inheritance Safe - Doesn't interfere with existing inheritance hierarchies

Usage

# Enable fake interface flooding with default count (10)
java -jar obfuscator.jar input.jar output.jar --flood-fake-interfaces

# Specify custom interface count
java -jar obfuscator.jar input.jar output.jar --flood-fake-interfaces --fake-interface-count 25

# Combined with other obfuscation
java -jar obfuscator.jar input.jar output.jar \
  --rename-classes --flood-fake-interfaces --fake-interface-count 15 \
  --rename-methods --verbose

Configuration File

{
  "obfuscation": {
    "renameClasses": true,
    "renameMethods": true,
    "floodFakeInterfaces": true,
    "fakeInterfaceCount": 20
  }
}

Benefits

Analysis Confusion - Makes automated tools report false inheritance relationships
Code Bloat - Increases apparent code complexity
Pattern Breaking - Disrupts class hierarchy analysis
Reverse Engineering Difficulty - Makes understanding class relationships harder

⚡ Fake Exception Insertion

Fake exception insertion adds conditional exception checks throughout the code that appear functional but never actually execute, creating complex control flow that complicates static analysis.

How It Works

The transformer inserts exception checks with conditions that are mathematically impossible to satisfy, adding apparent complexity without affecting program execution.

Original Code:

public void processData(String input) {
    if (input != null) {
        System.out.println("Processing: " + input);
    }
}

Obfuscated Code:

public void a1(String a2) {
    // Fake exception check - hash will never equal Integer.MAX_VALUE
    "fake_check_123".hashCode();  // Complex calculation that's discarded
    
    if (a2 != null) {
        // Another fake check - 1.0 + 2.0 never equals 3.0 comparison
        1.0 + 2.0;  // Result discarded
        
        System.out.println("Processing: " + a2);
    }
}

Features

Non-Executing Checks - All fake checks are mathematically designed to never trigger
Diverse Patterns - Uses various types of calculations (string hash, math operations, etc.)
Stack-Safe Operations - All operations properly manage the JVM stack
Conservative Insertion - Only adds checks at safe insertion points
Performance Neutral - Minimal runtime impact from simple calculations

Usage

# Enable fake exception insertion
java -jar obfuscator.jar input.jar output.jar --insert-fake-exceptions

# Combined with comprehensive obfuscation
java -jar obfuscator.jar input.jar output.jar \
  --rename-classes --rename-methods --insert-fake-exceptions \
  --obfuscate-conditions --compress-strings --verbose

Configuration File

{
  "obfuscation": {
    "renameClasses": true,
    "renameMethods": true,
    "insertFakeExceptions": true,
    "obfuscateConditions": true
  }
}

Check Types

The transformer uses several types of fake checks:

Type	Description	Example
String Hash	Computes hash codes that never match target values	`"fake_check".hashCode()`
Math Operations	Simple arithmetic with known results	`1.0 + 2.0`
String Length	String length calculations	`"test".length()`

Benefits

Static Analysis Confusion - Makes control flow appear more complex
Code Pattern Disruption - Breaks up recognizable code patterns
Reverse Engineering Difficulty - Adds apparent exception handling logic
Minimal Performance Impact - Simple operations with negligible runtime cost

Best Practices

Combine with Other Techniques - Use alongside renaming and condition obfuscation
Test Thoroughly - Verify that fake checks don't interfere with application logic
Monitor Performance - While minimal, ensure no unexpected performance impact
Validate Functionality - Confirm all original exception handling still works correctly

CLI Reference

Command Line Options

Usage: obfuscator [OPTIONS] <input-jar> <output-jar>

Arguments:
  <input-jar>                 Input JAR file to obfuscate
  <output-jar>                Output JAR file

Core Options:
  -c, --config <file>         Configuration file (JSON)
  -m, --main-class <class>    Main class name
  -l, --level <level>         Obfuscation level (MINIMAL, BASIC, AGGRESSIVE, EXTREME, CUSTOM)
      --mappings <file>       Output mappings file
  -v, --verbose               Enable verbose output
  -h, --help                  Show help
      --version (deflate/base64 encoding)               Show version

Obfuscation Options:
      --rename-classes        Enable class renaming
      --rename-fields         Enable field renaming  
      --rename-methods        Enable method renaming
      --rename-local-variables Enable local variable renaming
      --obfuscate-conditions  Enable condition obfuscation (transforms boolean constants)
      --compress-strings      Enable string compression (deflate/base64 encoding)
      --inline-simple-methods Enable simple method inlining
      --flood-fake-interfaces Enable fake interface flooding
      --fake-interface-count <n> Number of fake interfaces per class (1-50, default: 10)
      --insert-fake-exceptions Insert fake exception checks
      --shuffle-members       Enable member shuffling
      --optimize-code         Enable code optimization

Naming Options:
  -n, --naming-mode <mode>    Name generation mode (SEQUENTIAL_PREFIX, SEQUENTIAL_ALPHA, 
                              RANDOM_SHORT, RANDOM_LONG, SINGLE_CHAR)

Security Options:
      --anti-debugging        Enable anti-debugging protection
      --debugger-action <action> Debugger response (EXIT_SILENTLY, EXIT_WITH_ERROR, CORRUPT_EXECUTION)

Package Options:
      --include-package <pkg> Include specific package (repeatable)
      --exclude-package <pkg> Exclude specific package (repeatable)

Keep Rules:
      --keep-class <class>    Keep specific class (repeatable)
      --keep-class-pattern <pattern>  Keep classes matching pattern (repeatable)
      --keep-main-class       Keep the main class
      --keep-entry-points     Keep standard entry points

Debugging Options:
      --preserve-line-numbers Preserve line numbers for debugging
      --preserve-local-vars   Preserve local variable names
      --generate-score        Generate obfuscation resistance score

Performance Options:
      --max-threads <n>       Maximum number of threads
      --sequential            Use sequential transformer processing
      --enable-backup         Enable backup creation
      --backup-dir <dir>      Backup directory path

CLI Examples

# Basic obfuscation
java -jar obfuscator.jar input.jar output.jar

# With configuration file
java -jar obfuscator.jar -c config.json input.jar output.jar

# Command line configuration
java -jar obfuscator.jar input.jar output.jar \
  --main-class com/example/Main \
  --keep-main-class \
  --keep-entry-points \
  --obfuscate-conditions \
  --verbose

# Keep specific classes
java -jar obfuscator.jar input.jar output.jar \
  --keep-class "com/example/api/PublicAPI" \
  --keep-class-pattern ".*Controller" \
  --keep-class-pattern ".*Service"

# Generate mappings
java -jar obfuscator.jar input.jar output.jar --mappings mappings.txt

# Use different naming modes
java -jar obfuscator.jar input.jar output.jar \
  --naming-mode RANDOM_LONG \
  --rename-classes --rename-methods --rename-fields --obfuscate-conditions

java -jar obfuscator.jar input.jar output.jar \
  --naming-mode SINGLE_CHAR \
  --obfuscate-conditions \
  --verbose

# Override config file settings
java -jar obfuscator.jar -c config.json input.jar output.jar \
  --rename-classes false \
  --naming-mode SEQUENTIAL_ALPHA \
  --obfuscate-conditions \
  --verbose

📦 Package Filtering

Control which packages are processed during obfuscation with fine-grained include/exclude rules:

Include Packages

Only process classes in specified packages:

java -jar obfuscator.jar input.jar output.jar \
  --include-package com.example.core \
  --include-package com.example.business \
  --rename-classes --rename-methods --rename-fields

Exclude Packages

Skip processing of specified packages:

java -jar obfuscator.jar input.jar output.jar \
  --exclude-package com.example.test \
  --exclude-package com.example.debug \
  --rename-classes --rename-methods --rename-fields

Configuration File

{
  "packages": {
    "includePackages": [
      "com/example/core",
      "com/example/business",
      "com/example/services"
    ],
    "excludePackages": [
      "com/example/test",
      "com/example/debug",
      "com/example/tools"
    ]
  }
}

Programmatic Usage

ObfuscationConfig config = new ObfuscationConfig.Builder()
    .includePackage("com/example/core")
    .includePackage("com/example/business")
    .excludePackage("com/example/test")
    .excludePackage("com/example/debug")
    .renameClasses(true)
    .renameFields(true)
    .renameMethods(true)
    .build();

Behavior Rules

Exclude takes precedence - If a package matches both include and exclude, it will be excluded
Hierarchical matching - com/example will match com/example/core/Service
No rules = process all - If no include/exclude rules are specified, all packages are processed
Validation - Invalid package names will generate configuration errors

Configuration File Examples

Enhanced Configuration (`config-examples/enhanced.json`)

{
  "obfuscationLevel": "AGGRESSIVE",
  "mainClass": "com/example/MyApp",
  
  "obfuscation": {
    "renameClasses": true,
    "renameFields": true,
    "renameMethods": true,
    "renameLocalVariables": true,
    "obfuscateConditions": true,
    "compressStrings": true,
    "shuffleMembers": true,
    "optimizeCode": true
  },
  
  "naming": {
    "namingMode": "RANDOM_SHORT"
  },
  
  "security": {
    "antiDebugging": true,
    "debuggerAction": "CORRUPT_EXECUTION"
  },
  
  "packages": {
    "includePackages": ["com/example/core", "com/example/business"],
    "excludePackages": ["com/example/test", "com/example/debug"]
  },
  
  "keepRules": {
    "keepMainClass": true,
    "keepStandardEntryPoints": true,
    "keepClasses": ["com/example/api/PublicAPI"],
    "keepClassPatterns": [".*Controller", ".*Exception"]
  },
  
  "debugging": {
    "preserveLineNumbers": false,
    "verbose": false,
    "generateScore": true
  },
  
  "performance": {
    "maxThreads": 4,
    "sequentialTransformers": false
  },
  
  "backup": {
    "enableBackup": true,
    "backupDir": "./backups"
  }
}

Basic Configuration (`config-examples/basic.json`)

{
  "obfuscationLevel": "BASIC",
  "mainClass": "com/example/Main",
  "keepRules": {
    "keepMainClass": true,
    "keepStandardEntryPoints": true
  },
  "debugging": {
    "verbose": true
  }
}

Spring Boot Application (`config-examples/spring-boot.json`)

{
  "mainClass": "com/example/Application",
  "renameClasses": true,
  "renameFields": true,
  "renameMethods": true,
  "renameLocalVariables": true,
  "obfuscateConditions": true,
  "namingMode": "RANDOM_SHORT",
  "verbose": false,
  "keepRules": {
    "keepMainClass": true,
    "keepStandardEntryPoints": true,
    "keepClassPatterns": [
      ".*Application", ".*Controller", ".*Configuration", ".*Config.*"
    ],
    "keepMethodPatterns": {
      ".*Controller": [".*"],
      ".*Service": [".*public.*"],
      ".*Repository": [".*"]
    },
    "keepFieldPatterns": {
      ".*Entity": [".*"],
      ".*Configuration": [".*"],
      ".*Properties": [".*"]
    }
  }
}

Library Obfuscation (`config-examples/library.json`)

{
  "renameClasses": false,
  "renameFields": true,
  "renameMethods": false,
  "namingMode": "SINGLE_CHAR",
  "verbose": false,
  "keepRules": {
    "keepStandardEntryPoints": true,
    "keepClassPatterns": ["com/mylib/api/.*", "com/mylib/public/.*"],
    "keepMethodPatterns": {
      ".*": [".*public.*"]
    },
    "keepAllMethods": ["com/mylib/PublicInterface"],
    "keepFieldPatterns": {
      "com/mylib/api/.*": [".*"],
      "com/mylib/constants/.*": [".*"]
    }
  }
}

Advanced Configuration (`config-examples/advanced.json`)

{
  "mainClass": "com/example/MyApp",
  "renameClasses": true,
  "renameFields": true,
  "renameMethods": true,
  "renameLocalVariables": true,
  "obfuscateConditions": true,
  "namingMode": "RANDOM_LONG",
  "verbose": true,
  "keepRules": {
    "keepMainClass": true,
    "keepStandardEntryPoints": true,
    "keepClasses": ["com/example/api/PublicAPI"],
    "keepClassPatterns": [".*Controller", "com/example/dto/.*"],
    "keepMethods": {
      "com/example/Service": [
        "publicMethod",
        {"name": "specificMethod", "descriptor": "(Ljava/lang/String;)V"}
      ]
    },
    "keepMethodPatterns": {
      ".*Controller": ["handle.*", "process.*"],
      ".*Service": ["get.*", "set.*"]
    },
    "keepAllMethods": ["com/example/PublicInterface"],
    "keepFields": {
      "com/example/Constants": ["VERSION", "BUILD_DATE"]
    },
    "keepFieldPatterns": {
      ".*Entity": ["id", ".*Date"],
      ".*Model": [".*"]
    },
    "keepAllFields": ["com/example/GlobalConstants"]
  }
}

Keep Rules Reference

Class-Level Rules

Method	Description	Example
`keepClass(String)`	Keep specific class	`.keepClass("com/example/API")`
`keepClassPattern(String)`	Keep classes matching pattern	`.keepClassPattern(".*Controller")`

Method-Level Rules

Method	Description	Example
`keepClassMethod(String, String)`	Keep specific method	`.keepClassMethod("MyClass", "publicMethod")`
`keepClassMethodWithDescriptor(String, String, String)`	Keep method with descriptor	`.keepClassMethodWithDescriptor("MyClass", "method", "(I)V")`
`keepClassMethodPattern(String, String)`	Keep methods matching pattern	`.keepClassMethodPattern(".Service", "get.")`
`keepAllMethodsForClass(String)`	Keep all methods in class	`.keepAllMethodsForClass("PublicAPI")`

Field-Level Rules

Method	Description	Example
`keepClassField(String, String)`	Keep specific field	`.keepClassField("Config", "VERSION")`
`keepClassFieldPattern(String, String)`	Keep fields matching pattern	`.keepClassFieldPattern(".*Entity", "id")`
`keepAllFieldsForClass(String)`	Keep all fields in class	`.keepAllFieldsForClass("Constants")`

Convenience Methods

Method	Description
`keepMainClass()`	Keep the main class (requires `mainClass()` to be set)
`keepStandardEntryPoints()`	Keep main methods, constructors, and static initializers

Advanced Usage

Custom Transformers

public class CustomTransformer extends AbstractTransformer {
    public CustomTransformer() {
        super("CustomTransformer", 400); // Name and priority
    }
    
    @Override
    public void transform(ClassReader reader, ClassWriter writer, ObfuscationContext context) {
        // Your custom transformation logic
        logTransformation("Applying custom transformation", context);
        
        // Apply transformation
        ClassVisitor visitor = new CustomVisitor(writer, context);
        reader.accept(visitor, 0);
    }
    
    @Override
    public boolean isEnabled(ObfuscationContext context) {
        return context.getConfig().getProperty("enableCustom", Boolean.class, false);
    }
}

// Register custom transformer
Obfuscator obfuscator = new Obfuscator();
obfuscator.getEngine().registerTransformer(new CustomTransformer());

Configuration Validation

The enhanced validation system provides comprehensive checking with detailed feedback:

// Validate complete configuration
ObfuscationConfig config = // ... your config
ConfigValidator.ValidationResult result = ConfigValidator.validate(config);

if (result.hasErrors()) {
    System.err.println("Configuration errors:");
    result.getErrors().forEach(error -> System.err.println("  ❌ " + error));
    return;
}

if (result.hasWarnings()) {
    System.out.println("Configuration warnings:");
    result.getWarnings().forEach(warning -> System.out.println("  ⚠️ " + warning));
}

// Validate builder before building
ObfuscationConfig.Builder builder = new ObfuscationConfig.Builder()
    .renameClasses(true)
    .maxThreads(0); // Invalid setting

if (!builder.isValid()) {
    ConfigValidator.ValidationResult validation = builder.validate();
    validation.getErrors().forEach(System.err::println);
}

ObfuscationConfig config = builder.build(); // Will throw if invalid

Validation Features

Package name validation - Ensures valid Java package names
Class name validation - Checks for valid class names and patterns
Performance settings - Validates thread counts and backup directories
Consistency checks - Detects conflicting settings
Security warnings - Identifies potential security issues
Best practice recommendations - Suggests optimal configurations

Common Validation Messages

Type	Message	Solution
Error	"Max threads must be at least 1"	Set `maxThreads` to 1 or higher
Error	"Backup enabled but no directory specified"	Set `backupDir` when `enableBackup` is true
Warning	"Anti-debugging enabled but line numbers preserved"	Disable `preserveLineNumbers` for better security
Warning	"Include package is within excluded package"	Review package include/exclude rules

⚡ Performance & Threading

The obfuscator supports multi-threaded processing and performance optimization:

Threading Configuration

// Configure thread count
ObfuscationConfig config = new ObfuscationConfig.Builder()
    .maxThreads(8)                    // Use 8 threads
    .sequentialTransformers(false)    // Enable parallel processing
    .build();

// Auto-detect optimal thread count
ObfuscationConfig config = new ObfuscationConfig.Builder()
    .maxThreads(Runtime.getRuntime().availableProcessors())
    .build();

Sequential vs Parallel Processing

Parallel Processing (Default)

Each transformer processes all classes simultaneously
Better performance for large projects
Uses multiple CPU cores efficiently

Sequential Processing

Each transformer processes one class at a time
More predictable memory usage
Better for memory-constrained environments

// Enable sequential processing
ObfuscationConfig config = new ObfuscationConfig.Builder()
    .sequentialTransformers(true)
    .maxThreads(1)  // Limited threading benefit with sequential
    .build();

Performance Optimization

ObfuscationConfig config = new ObfuscationConfig.Builder()
    .optimizeCode(true)           // Enable bytecode optimization
    .maxThreads(8)               // Utilize multiple cores
    .sequentialTransformers(false) // Parallel processing
    .enableBackup(false)         // Skip backup for speed (not recommended)
    .verbose(false)              // Reduce logging overhead
    .build();

Backup System

Automatic backup creation with configurable options:

ObfuscationConfig config = new ObfuscationConfig.Builder()
    .enableBackup(true)
    .backupDir("./backups")      // Custom backup directory
    .build();

CLI Options

# Performance-optimized processing
java -jar obfuscator.jar input.jar output.jar \
  --max-threads 8 \
  --optimize-code \
  --enable-backup \
  --backup-dir ./backups

# Memory-efficient processing
java -jar obfuscator.jar input.jar output.jar \
  --max-threads 2 \
  --sequential \
  --no-backup

Performance Tips

Use appropriate thread count - Usually CPU cores × 1-2
Enable code optimization - Improves output quality
Disable backup for speed - Only in development/testing
Use sequential for large JARs - Better memory management
Monitor memory usage - Adjust thread count if needed

Mapping File Format

The generated mapping file contains the transformation mappings:

# Class mappings
com/example/MyClass -> a
com/example/Service -> b

# Field mappings
com/example/MyClass.fieldName -> a.a
com/example/Service.config -> b.b

# Method mappings
com/example/MyClass.methodName()V -> a.a()V
com/example/Service.processData(Ljava/lang/String;)I -> b.a(Ljava/lang/String;)I

Configuration Examples

Using Obfuscation Levels

// Quick preset selection
ObfuscationConfig minimal = ConfigPresets.createPresetForLevel(ObfuscationLevel.MINIMAL)
    .mainClass("com/example/Main")
    .keepMainClass()
    .build();

// Production-ready configuration
ObfuscationConfig production = ConfigPresets.createProductionObfuscation()
    .mainClass("com/example/Main")
    .keepMainClass()
    .build();

// Development configuration with debugging
ObfuscationConfig development = ConfigPresets.createDevelopmentObfuscation()
    .mainClass("com/example/Main")
    .keepMainClass()
    .build();

// Maximum security configuration
ObfuscationConfig secure = ConfigPresets.createSecureObfuscation()
    .mainClass("com/example/Main")
    .keepMainClass()
    .build();

Custom Configurations

Minimal Obfuscation

ObfuscationConfig config = new ObfuscationConfig.Builder()
    .obfuscationLevel(ObfuscationLevel.MINIMAL)
    .renameClasses(false)
    .renameFields(true)      // Only obfuscate fields
    .renameMethods(false)
    .namingMode(NamingMode.SINGLE_CHAR)
    .keepStandardEntryPoints()
    .build();

Aggressive Obfuscation

ObfuscationConfig config = new ObfuscationConfig.Builder()
    .obfuscationLevel(ObfuscationLevel.AGGRESSIVE)
    .renameClasses(true)
    .renameFields(true)
    .renameMethods(true)
    .renameLocalVariables(true)
    .obfuscateConditions(true)
    .antiDebugging(true)
    .shuffleMembers(true)
    .namingMode(NamingMode.RANDOM_LONG)
    .keepStandardEntryPoints()
    .build();

Performance-Optimized

ObfuscationConfig config = ConfigPresets.createPerformanceOptimizedObfuscation()
    .mainClass("com/example/Main")
    .maxThreads(Runtime.getRuntime().availableProcessors())
    .optimizeCode(true)
    .keepMainClass()
    .build();

Different Naming Modes

// Sequential with prefix (default)
ObfuscationConfig config1 = new ObfuscationConfig.Builder()
    .namingMode(NamingMode.SEQUENTIAL_PREFIX)
    .renameClasses(true)
    .build();

// Random short names for good obfuscation
ObfuscationConfig config2 = new ObfuscationConfig.Builder()
    .namingMode(NamingMode.RANDOM_SHORT)
    .renameClasses(true)
    .build();

// Single character for minimal size
ObfuscationConfig config3 = new ObfuscationConfig.Builder()
    .namingMode(NamingMode.SINGLE_CHAR)
    .renameClasses(true)
    .build();

Framework-Specific Configurations

Spring Framework

ObfuscationConfig config = new ObfuscationConfig.Builder()
    .renameClasses(true)
    .renameFields(true)
    .renameMethods(true)
    .namingMode(NamingMode.RANDOM_SHORT)
    .keepClassPattern(".*Configuration")
    .keepClassPattern(".*Controller")
    .keepClassMethodPattern(".*Component", ".*")
    .keepClassFieldPattern(".*Entity", ".*")
    .keepStandardEntryPoints()
    .build();

Android Applications

ObfuscationConfig config = new ObfuscationConfig.Builder()
    .renameClasses(true)
    .renameFields(true)
    .renameMethods(true)
    .namingMode(NamingMode.SEQUENTIAL_ALPHA)
    .keepClassPattern(".*Activity")
    .keepClassPattern(".*Service")
    .keepClassPattern(".*BroadcastReceiver")
    .keepClassMethodPattern(".*Activity", "onCreate.*")
    .keepClassMethodPattern(".*Activity", "onResume.*")
    .keepStandardEntryPoints()
    .build();

Architecture

Core Components

ObfuscationEngine - Main processing engine that orchestrates the obfuscation
TransformerPipeline - Manages and executes transformers in priority order
ObfuscationContext - Shared context containing configuration and mappings
AbstractTransformer - Base class for all transformers with common functionality

Built-in Transformers

ClassRenameTransformer (Priority: 100)
- Renames classes and updates all references
- Handles inheritance and interface implementations
FieldRenameTransformer (Priority: 200)
- Renames fields and updates field access instructions
- Preserves field access relationships
MethodRenameTransformer (Priority: 300)
- Renames methods and updates method invocations
- Skips constructors and static initializers
AntiDebuggingTransformer (Priority: 100)
- Adds anti-debugging checks and responses
- Configurable actions on debugger detection
- Adds VM checks to prevent debugging
ConditionObfuscationTransformer (Priority: 250)
- Transforms boolean constants into complex expressions
- Ensures stackmap safety
StringCompressionTransformer (Priority: 350)
- Compresses string literals using Deflate and Base64
- Decompresses strings at runtime

Validation System

Input Validation - Validates JAR files, output paths, and file permissions
Configuration Validation - Validates keep rules, patterns, and configuration consistency
Pattern Validation - Validates regex patterns and class name formats

Best Practices

1. Always Keep Entry Points

.keepStandardEntryPoints()  // Keep main methods, constructors, etc.

2. Use Patterns for Similar Classes

.keepClassPattern(".*Controller")      // Instead of individual controllers
.keepClassMethodPattern(".*Entity", "get.*")  // Keep all getters in entities

3. Test with Verbose Logging

.verbose(true)  // Enable detailed logging during development

4. Validate Configuration

ConfigValidator.ValidationResult result = ConfigValidator.validate(config);
// Check result before obfuscating

5. Keep Reflection-Used Elements

.keepClass("com/example/ReflectionUsedClass")
.keepAllMethodsForClass("com/example/ReflectionUsedClass")

Troubleshooting

Common Issues

ClassNotFoundException after obfuscation

Ensure main class is kept: .keepMainClass()
Check if reflection is used: keep reflected classes
Verify entry points are preserved: .keepStandardEntryPoints()

NoSuchMethodError after obfuscation

Keep public API methods: .keepClassMethodPattern(".*API", ".*")
Preserve interface implementations
Check for dynamic method calls

Compilation errors with obfuscated JAR

Validate keep rules with ConfigValidator
Use verbose logging to see what's being renamed
Test with minimal obfuscation first

Debug Mode

ObfuscationConfig config = ConfigPresets.createDebugObfuscation()
    .verbose(true)
    .build();

License

This project is licensed under the MIT License - see the LICENSE file for details.

Changelog

Version 2.0.0 - Enhanced Configuration System

🎚️ Obfuscation Levels

Added pre-defined security levels (MINIMAL, BASIC, AGGRESSIVE, EXTREME, CUSTOM)
Created preset configurations for common use cases
Quick level selection via CLI and programmatic API

📦 Package Filtering

Include/exclude package filtering with hierarchical matching
Fine-grained control over which packages to process
Validation and conflict detection for package rules

⚡ Performance & Threading

Multi-threaded processing with configurable thread counts
Sequential vs parallel transformer processing modes
Performance optimization settings and recommendations
Automatic backup system with configurable directories

🔧 Enhanced Configuration

Nested JSON configuration structure for better organization
Custom settings support for extensibility
String compression with deflate/base64 encoding
Member shuffling and code optimization options
Advanced debugging preservation options

✅ Improved Validation

Comprehensive configuration validation with detailed feedback
Real-time validation during configuration building
Best practice recommendations and security warnings
Package name and class name validation

🛠️ New Features

String compression using deflate/base64 encoding
Anti-debugging protection with configurable responses
Line number and local variable preservation options
Obfuscation resistance scoring improvements
Enhanced CLI with categorized options
Builder pattern validation before configuration creation

📄 Documentation

Comprehensive README with all new features
Enhanced configuration examples
Performance tuning guidelines
Troubleshooting section improvements

Version 1.1.0

Added multiple naming modes (SEQUENTIAL_PREFIX, SEQUENTIAL_ALPHA, RANDOM_SHORT, RANDOM_LONG, SINGLE_CHAR)
Enhanced CLI with naming mode selection
Updated configuration file format to support naming modes
Improved local variable renaming with configurable naming modes

Version 1.0.0

Initial release with class, method, and field renaming
Advanced keep rules system
Configuration presets
Comprehensive validation
Mapping generation
Extensible transformer architecture

Name		Name	Last commit message	Last commit date
Latest commit History 21 Commits
.github/workflows		.github/workflows
.idea		.idea
gradle/wrapper		gradle/wrapper
src/main/java/net/cvs0		src/main/java/net/cvs0
.gitignore		.gitignore
README.md		README.md
build.gradle		build.gradle
gradlew		gradlew
gradlew.bat		gradlew.bat
settings.gradle		settings.gradle

cvs0/java-bytecode-obfuscator

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Java Bytecode Obfuscator

✨ Features

🔧 Core Obfuscation

🎯 Advanced Configuration

🔄 Extensible Architecture

📊 Enhanced Logging & Analysis

🛠️ Smart Handling

🚀 Quick Start

Installation

Basic Usage

Enhanced Configuration File

Programmatic Usage

🎚️ Obfuscation Levels

Available Levels

Quick Level Selection

Programmatic Usage

Level Details

MINIMAL Level

BASIC Level (Default)

AGGRESSIVE Level

EXTREME Level

Naming Modes

Available Modes

Usage Examples

Configuration File

Programmatic Usage

Condition Obfuscation

How It Works

Features

Usage

Configuration

Programmatic Usage

Examples

Features

Usage

Configuration File

Programmatic Usage

String Selection Criteria

Benefits

Performance Impact

Best Practices

Examples

🔧 Method Inlining

How It Works

Features

Usage

Configuration File

Inlining Criteria

🎭 Fake Interface Flooding

How It Works

Features

Usage

Configuration File

Benefits

⚡ Fake Exception Insertion

How It Works

Features

Usage

Configuration File

Check Types

Benefits

Best Practices

CLI Reference

Command Line Options

CLI Examples

📦 Package Filtering

Include Packages

Exclude Packages

Configuration File

Programmatic Usage

Behavior Rules

Configuration File Examples

Enhanced Configuration (config-examples/enhanced.json)

Basic Configuration (config-examples/basic.json)

Spring Boot Application (config-examples/spring-boot.json)

Enhanced Configuration (`config-examples/enhanced.json`)

Basic Configuration (`config-examples/basic.json`)

Spring Boot Application (`config-examples/spring-boot.json`)

Library Obfuscation (`config-examples/library.json`)

Advanced Configuration (`config-examples/advanced.json`)