> For the complete documentation index, see [llms.txt](https://netguard.gitbook.io/help/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://netguard.gitbook.io/help/5.8.1.1/protections/code-protection/msil-code-encryption.md).

# MSIL Code Encryption

Preventing hackers from accessing your code is our main priority. 

NETGuard.IO extract your method's MSIL instructions and encrypt them, the given data is injected into your file's header. The data is decoded at runtime when a checksum is validated. 

This protection produces unverifiable modules. 

This protection serves an anti tampering purpose. 

This protection includes simple anti debugging checksum.

{% tabs %}
{% tab title="BEFORE" %}

```csharp
// RegExTester.Program
// Token: 0x0600002F RID: 47 RVA: 0x00003417 File Offset: 0x00002417
[STAThread]
private static void Main()
{
	Application.EnableVisualStyles();
	Application.SetCompatibleTextRenderingDefault(false);
	Application.Run(new frmMain());
}
```

{% endtab %}

{% tab title="AFTER" %}

```csharp
// RegExTester.Program
// Token: 0x0600002F RID: 47 RVA: 0x00003417 File Offset: 0x00002417
[STAThread]
private static void Main()
{
	/*
	An exception occurred when decompiling this method (0600000A)
	
	ICSharpCode.Decompiler.DecompilerException: Error decompiling System.Void _test.Program::.ctor()
	 ---> System.ArgumentOutOfRangeException: Non-negative number required.
	Parameter name: length
	   at System.Array.Copy(Array sourceArray, Int32 sourceIndex, Array destinationArray, Int32 destinationIndex, Int32 length, Boolean reliable)
	   at System.Array.Copy(Array sourceArray, Array destinationArray, Int32 length)
	   at ICSharpCode.Decompiler.ILAst.ILAstBuilder.StackSlot.ModifyStack(StackSlot[] stack, Int32 popCount, Int32 pushCount, ByteCode pushDefinition) in C:\projects\dnspy\Extensions\ILSpy.Decompiler\ICSharpCode.Decompiler\ICSharpCode.Decompiler\ILAst\ILAstBuilder.cs:line 50
	   at ICSharpCode.Decompiler.ILAst.ILAstBuilder.StackAnalysis(MethodDef methodDef) in C:\projects\dnspy\Extensions\ILSpy.Decompiler\ICSharpCode.Decompiler\ICSharpCode.Decompiler\ILAst\ILAstBuilder.cs:line 373
	   at ICSharpCode.Decompiler.ILAst.ILAstBuilder.Build(MethodDef methodDef, Boolean optimize, DecompilerContext context) in C:\projects\dnspy\Extensions\ILSpy.Decompiler\ICSharpCode.Decompiler\ICSharpCode.Decompiler\ILAst\ILAstBuilder.cs:line 264
	   at ICSharpCode.Decompiler.Ast.AstMethodBodyBuilder.CreateMethodBody(IEnumerable`1 parameters, MethodDebugInfoBuilder& builder) in C:\projects\dnspy\Extensions\ILSpy.Decompiler\ICSharpCode.Decompiler\ICSharpCode.Decompiler\Ast\AstMethodBodyBuilder.cs:line 105
	   at ICSharpCode.Decompiler.Ast.AstMethodBodyBuilder.CreateMethodBody(MethodDef methodDef, DecompilerContext context, IEnumerable`1 parameters, Boolean valueParameterIsKeyword, StringBuilder sb, MethodDebugInfoBuilder& stmtsBuilder) in C:\projects\dnspy\Extensions\ILSpy.Decompiler\ICSharpCode.Decompiler\ICSharpCode.Decompiler\Ast\AstMethodBodyBuilder.cs:line 83
	   --- End of inner exception stack trace ---
	   at ICSharpCode.Decompiler.Ast.AstMethodBodyBuilder.CreateMethodBody(MethodDef methodDef, DecompilerContext context, IEnumerable`1 parameters, Boolean valueParameterIsKeyword, StringBuilder sb, MethodDebugInfoBuilder& stmtsBuilder) in C:\projects\dnspy\Extensions\ILSpy.Decompiler\ICSharpCode.Decompiler\ICSharpCode.Decompiler\Ast\AstMethodBodyBuilder.cs:line 87
	   at ICSharpCode.Decompiler.Ast.AstBuilder.CreateMethodBody(MethodDef method, IEnumerable`1 parameters, Boolean valueParameterIsKeyword, MethodKind methodKind, MethodDebugInfoBuilder& builder) in C:\projects\dnspy\Extensions\ILSpy.Decompiler\ICSharpCode.Decompiler\ICSharpCode.Decompiler\Ast\AstBuilder.cs:line 1358
	
	*/;
}
```

{% endtab %}
{% endtabs %}