JNVM - Java Native VM Protector

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A powerful Java bytecode protection tool that converts Java methods into native code execution, providing strong protection against decompilation and reverse engineering.

Features

• Native VM Execution: Converts Java bytecode to native code executed by a custom VM interpreter
• Opcode Obfuscation: Each bytecode instruction is mapped to a random opcode value, preventing easy reconstruction
• ChaCha20 Encryption: All bytecode and strings are encrypted using ChaCha20 stream cipher
• Cross-Platform: Supports multiple targets via Zig compiler (Windows, Linux, macOS, Android)
• INVOKEDYNAMIC Support: Support for lambda expressions and dynamic method invocation (experimental)

Warning: INVOKEDYNAMIC implementation is experimental and may contain bugs. Use with caution in production environments.

Requirements

• Java 8+
• Zig 0.11+ (for native compilation)
• Gradle 8+

Usage

Configuration File

Create a config.yml file:

# Input JAR file
jar: test/app.jar

# Output JAR file
out: test/app-protected.jar

# Protection rules
protect:
  - "**"  # Protect all methods

# Target platforms
targets:
  - x86_64-windows-gnu

# Options
debug: false
native-dir: native
protect-bootstrap-payload: false
direct-native-rewrite: false

Run

java -jar jnvm.jar config.yml

Protection Rules

Rule	Description
package.**	Protect all methods in package and subpackages
ClassName	Protect all methods in class
ClassName#methodName	Protect specific method
@annotation	Protect methods with annotation

direct-native-rewrite:

• false (default): Protect by rewriting method body to call bridge.
• true: Rewrite protected non-<clinit> methods to real native, and register per-class natives in that class <clinit>.

Before/After Example

Original Code

package pack.tests.reflects.annot;
import java.lang.reflect.Field;
import pack.tests.reflects.annot.anno;
public class annoe {
    @anno(val="PASS")
    private static final String fail = "WHAT";
    @anno
    public void dox() throws Exception {
        String toGet = "FAIL";
        for (Field f : annoe.class.getDeclaredFields()) {
            f.setAccessible(true);
            anno obj = f.getAnnotation(anno.class);
            if (obj == null) continue;
            toGet = obj.val();
        }
        System.out.println(toGet);
    }
    @anno(val="no")
    public void dov() {
        System.out.println("FAIL");
    }
}

Protected Code

package pack.tests.reflects.annot;
import lib.xml.abc.Dispatcher;
import pack.tests.reflects.annot.anno;
public class annoe {
   @anno(val="PASS")
   private static final String fail = "WHAT";
   @anno
   public void dox() throws Exception {
      Dispatcher.executeVoid(1282844577, new Object[]{this, annoe.class});
   }
   @anno(val="no")
   public void dov() {
      Dispatcher.executeVoid(1282844576, new Object[]{this, annoe.class});
   }
}

The original method bodies are replaced with native VM calls, making reverse engineering extremely difficult.

How It Works

1. Scanning: Analyzes the input JAR to find methods matching protection rules
2. Encryption: Encrypts bytecode using ChaCha20 with unique keys per method
3. Code Generation: Generates C source files:
   • vm_types.h - VM type definitions
   • vm_data.c - Encrypted method data and string pool
   • vm_interpreter.c - Custom bytecode interpreter
   • vm_bridge.c - JNI bridge with RegisterNatives
4. Compilation: Compiles native code using Zig for specified targets
5. Patching: Rewrites protected methods to call the native VM
6. Packaging: Embeds native libraries into the output JAR

Compatibility

JNVM has been tested with JARs obfuscated by:

• Zelix KlassMaster (ZKM) - support including encrypted string decryption , invokedynamic
• ProGuard - Standard obfuscation
• Allatori - String encryption and flow obfuscation
• Vanilla Java - No obfuscation

Supported Bytecode Instructions (190/202 opcodes)

Constants (19 opcodes)

NOP, ACONST_NULL, ICONST_M1 to ICONST_5, LCONST_0, LCONST_1, FCONST_0 to FCONST_2, DCONST_0, DCONST_1, BIPUSH, SIPUSH, LDC, LDC_W, LDC2_W

Load/Store (50 opcodes)

ILOAD, LLOAD, FLOAD, DLOAD, ALOAD, ILOAD_0 to ILOAD_3, LLOAD_0 to LLOAD_3, FLOAD_0 to FLOAD_3, DLOAD_0 to DLOAD_3, ALOAD_0 to ALOAD_3, ISTORE, LSTORE, FSTORE, DSTORE, ASTORE, ISTORE_0 to ISTORE_3, LSTORE_0 to LSTORE_3, FSTORE_0 to FSTORE_3, DSTORE_0 to DSTORE_3, ASTORE_0 to ASTORE_3

Stack Operations (9 opcodes)

POP, POP2, DUP, DUP_X1, DUP_X2, DUP2, DUP2_X1, DUP2_X2, SWAP

Arithmetic (52 opcodes)

• Add/Sub/Mul/Div/Rem: IADD, LADD, FADD, DADD, ISUB, LSUB, FSUB, DSUB, IMUL, LMUL, FMUL, DMUL, IDIV, LDIV, FDIV, DDIV, IREM, LREM, FREM, DREM
• Negation: INEG, LNEG, FNEG, DNEG
• Bitwise/Shift: ISHL, LSHL, ISHR, LSHR, IUSHR, LUSHR, IAND, LAND, IOR, LOR, IXOR, LXOR
• Conversion: I2L, I2F, I2D, L2I, L2F, L2D, F2I, F2L, F2D, D2I, D2L, D2F, I2B, I2C, I2S
• Comparison: LCMP, FCMPL, FCMPG, DCMPL, DCMPG

Control Flow (26 opcodes)

• Conditional: IFEQ, IFNE, IFLT, IFGE, IFGT, IFLE, IF_ICMPEQ, IF_ICMPNE, IF_ICMPLT, IF_ICMPGE, IF_ICMPGT, IF_ICMPLE, IF_ACMPEQ, IF_ACMPNE, IFNULL, IFNONNULL
• Unconditional: GOTO, GOTO_W
• Switch: TABLESWITCH, LOOKUPSWITCH
• Return: RETURN, IRETURN, LRETURN, FRETURN, DRETURN, ARETURN
• Other: IINC, ATHROW

Object Operations (12 opcodes)

NEW, CHECKCAST, INSTANCEOF, GETFIELD, PUTFIELD, GETSTATIC, PUTSTATIC, INVOKEVIRTUAL, INVOKESPECIAL, INVOKESTATIC, INVOKEINTERFACE, INVOKEDYNAMIC

Array Operations (20 opcodes)

NEWARRAY, ANEWARRAY, MULTIANEWARRAY, ARRAYLENGTH, IALOAD, LALOAD, FALOAD, DALOAD, AALOAD, BALOAD, CALOAD, SALOAD, IASTORE, LASTORE, FASTORE, DASTORE, AASTORE, BASTORE, CASTORE, SASTORE

Monitor (2 opcodes)

MONITORENTER, MONITOREXIT

Not Implemented (12 opcodes)

Opcode	Reason
JSR, RET, JSR_W	Deprecated since Java 6
WIDE	Extended local variable indexing (rarely needed)
RET_* variants	Part of WIDE extension

Building from Source

git clone https://github.com/AlphaAutoLeak/jnvm.git
cd JNVM
./gradlew build

The compiled JAR will be in build/libs/.

License

This project is provided for educational and legitimate software protection purposes only.

Disclaimer

Use this tool responsibly. The authors are not responsible for any misuse or damage caused by this software.