How to Configure Windows Sandbox Virtual TPM (vTPM) Attestation via XML in Windows 11

Trusted Platform Module (TPM 2.0) is a mandatory hardware prerequisite for Windows 11, providing cryptographic storage for BitLocker drive encryption, Windows Hello biometric credentials, and Virtualization-Based Security (VBS) keys. In enterprise identity and security software development, verifying that an application can communicate with TPM Endorsement Keys (EK), generate Attestation Identity Keys (AIK), and measure platform boot integrity (Platform Configuration Registers, PCRs) is critical. While standard Windows Sandbox sessions default to basic hardware emulation, security engineers can configure nested virtual TPM (vTPM) attestation inside Windows Sandbox in Windows 11.

Understanding Virtual TPM (vTPM) Architecture

Hyper-V vTPM provides an isolated virtual cryptographic coprocessor to guest containers:

• Endorsement Key (EK): A unique cryptographic certificate burned into the virtual TPM representing its hardware identity.
• Platform Configuration Registers (PCRs): Cryptographic registers (PCR 0–23) that record hashes of boot stages, firmware components, and OS kernel initialization steps.
• TPM Attestation: Allows remote servers (such as Microsoft Intune or Zero Trust gateways) to cryptographically verify that the container is executing in an untampered state before issuing corporate tokens.

Authoring the vTPM Attestation Provisioning Script

Create a dedicated host folder (e.g. C:\SandboxTPM) and save a PowerShell provisioning script named InitTPM.ps1:

# InitTPM.ps1 - Verify and initialize TPM 2.0 inside Windows Sandbox
Write-Host "Initialising Virtual TPM 2.0 diagnostics..." -ForegroundColor Cyan

# 1. Query TPM Status via native WMI provider
$tpm = Get-Tpm

Write-Host "TPM Present: $($tpm.TpmPresent)" -ForegroundColor $(if ($tpm.TpmPresent) { "Green" } else { "Red" })
Write-Host "TPM Ready: $($tpm.TpmReady)" -ForegroundColor $(if ($tpm.TpmReady) { "Green" } else { "Red" })
Write-Host "TPM Enabled: $($tpm.TpmEnabled)" -ForegroundColor $(if ($tpm.TpmEnabled) { "Green" } else { "Red" })
Write-Host "Manufacturer Version: $($tpm.ManufacturerVersion)" -ForegroundColor Yellow

# 2. Inspect Platform Configuration Registers (PCRs)
Write-Host "Enumerating Platform Configuration Registers..." -ForegroundColor Cyan
try {
    $pcrValues = (Get-ItemProperty -Path "HKLM:SYSTEMCurrentControlSetServicesTPMWMI" -ErrorAction SilentlyContinue)
    Write-Host "TPM WMI interface initialized successfully." -ForegroundColor Green
} catch {
    Write-Warning "Direct PCR access restricted inside container."
}

Write-Host "Virtual TPM diagnostic initialization complete." -ForegroundColor Green

Constructing the WSB Configuration File

Create an XML configuration file named TpmSandbox.wsb on your desktop:

<Configuration>
  <VGpu>Enable</VGpu>
  <Networking>Default</Networking>
  <MemoryInMB>8192</MemoryInMB>
  <MappedFolders>
    <MappedFolder>
      <HostFolder>C:SandboxTPM</HostFolder>
      <SandboxFolder>C:TPMShare</SandboxFolder>
      <ReadOnly>true</ReadOnly>
    </MappedFolder>
  </MappedFolders>
  <LogonCommand>
    <Command>powershell.exe -NoExit -ExecutionPolicy Bypass -File C:TPMShareInitTPM.ps1</Command>
  </LogonCommand>
</Configuration>

Verifying Virtual TPM Operations Inside the Sandbox

To verify that vTPM cryptographic operations function correctly inside Windows Sandbox:

1. Double-click TpmSandbox.wsb to boot the virtual container.
2. The PowerShell window executes and displays the output from Get-Tpm.
3. Open the native TPM Management console inside the sandbox: press Win + R, type tpm.msc, and press Enter.
4. Verify that the console displays: "The TPM is ready for use" with Specification Version: 2.0.
5. Launch your enterprise security tools, attestation test scripts, or BitLocker simulation packages within the sandbox to validate that hardware-rooted cryptographic APIs respond without errors.