Concrete examples, recommended workflow, and short code snippets showing how the Vigorous control-flow algorithm in Skater .NET Obfuscator is typically applied. Where appropriate, this guide cites official Skater documentation and release notes.

The Vigorous algorithm is a control-flow obfuscation mode that performs deep rewriting of method bodies and control-flow graphs: reorders branches and basic blocks, splits/merges blocks, inserts dummy branches and state machines, and generally transforms clean IL into semantically equivalent but hard-to-follow code. This is intended to significantly raise the effort required for decompilation and human analysis.

Open your assembly in Skater → go to the Control Flow tab → choose the Vigorous algorithm for selected methods or modules. Save settings to an XML profile if you want repeatable runs.

Skater supports command-line options; common switches include flags to enable control flow for all methods or to provide an XML settings file exported from GUI.

REM Example: run Skater with settings file
Skater.exe -s:"C:\SkaterProfiles\MyVigorousProfile.xml" -in:"bin\Release\MyApp.dll" -out:"bin\Release\Obf\" -writeLog

(You can export the XML profile from the GUI, then reuse it in automated builds).

Instead of “all methods”, pick a handful of sensitive methods (license checks, cryptographic routines, business logic entry points). This reduces risk of breaking reflection/interop and keeps runtime overhead manageable.

Vigorous operates at the IL level; the decompiled C# output after Vigorous will usually be messy. The examples below show typical patterns you will see after Vigorous transformation (conceptual — actual output depends on many factors).

public int MultiplyIfPositive(int x, int y)
{
    if (x > 0)
        return x * y;
    return 0;
}

public int MultiplyIfPositive(int x, int y)
{
    int result = 0;
    int state = 1;
    while (true)
    {
        switch (state)
        {
            case 1:
                if (x <= 0) { state = 10; continue; }
                state = 2; continue;
            case 2:
                result = x * y ^ 0x0;   // dummy arithmetic inserted
                state = 99; continue;
            case 10:
                result = 0; state = 99; continue;
            case 99:
                return result;
        }
    }
}

Notes: dummy locals/ops, explicit state machine, unnatural branching and jumps are common artifacts. Real Vigorous output is often more complex (split blocks, extra exception handlers, flattened loops).

/* before */
public bool IsAdult(int age)
{
    return age >= 18;
}

/* conceptual Vigorous-style after */
public bool IsAdult(int a)
{
bool r = false;
int pc = 0;
for (;;)
{
switch (pc)
{
case 0:
if (a < 18) { pc = 5; continue; }
r = true; pc = 9; continue;
case 5:
r = false; pc = 9; continue;
case 9:
return r;
}
}
} 

1. Start small: apply Vigorous to one assembly and to a very limited set of methods (license check, algorithm core). Run tests.
2. Full test cycle: unit tests, integration tests, reflection/serialization checks, P/Invoke / interop scenarios, exception-path tests and performance benchmarks. Vigorous rewrites exception handling and IL shapes—so tests often find issues.
3. Keep clean fallback builds: keep un-obfuscated or lightly-obfuscated artifacts for debugging and rollback.
4. Document settings: save the Skater XML profile and record Skater version & profile used for each release (helps reproduce/diagnose). Release notes mention Vigorous improvements in recent updates — keep Skater updated.
5. Combine protections carefully: string encryption, renaming and control flow can be layered — but layering increases risk; validate after each added protection.

You can export a profile from the GUI. The snippet below shows the important ideas: selecting Vigorous control flow and listing methods you want to protect. (Actual tag names depend on the exact Skater XML schema — export from GUI to produce correct XML.)

<SkaterProject>
  <InputFile>bin\Release\MyApp.dll</InputFile>
  <OutputDirectory>bin\Release\Obf</OutputDirectory>

  <ControlFlow algorithm="Vigorous">
    <Enable>true</Enable>
    <Methods>
      <Method name="MyApp.Security.LicenseChecker.VerifyLicense"/> 
      <Method name="MyApp.Algo.CryptoEngine.Encrypt"/> 
    </Methods>
  </ControlFlow>

  <StringEncryption>true</StringEncryption>
  <RenameSymbols>true</RenameSymbols>
</SkaterProject>

• All unit tests passed on the obfuscated assembly
• Integration tests (including reflection & serialization) passed
• Manual smoke tests for UI, plugins and native interop
• Performance benchmarks acceptable (Vigorous can add runtime overhead)
• Logging/telemetry still useful for debugging field issues