Anthropic-Cybersecurity-Skills/skills/implementing-disk-encryption-with-bitlocker/SKILL.md

---
name: implementing-disk-encryption-with-bitlocker
description: >
  Implements full disk encryption using Microsoft BitLocker on Windows endpoints to protect
  data at rest from unauthorized access in case of device loss or theft. Use when deploying
  encryption for compliance requirements, securing mobile workstations, or implementing data
  protection controls across the enterprise. Activates for requests involving BitLocker
  encryption, disk encryption, TPM configuration, or data-at-rest protection.
domain: cybersecurity
subdomain: endpoint-security
tags: [endpoint, encryption, BitLocker, TPM, data-protection, windows-security]
version: 1.0.0
author: mahipal
license: MIT
---
# Implementing Disk Encryption with BitLocker

## When to Use

Use this skill when:
- Encrypting Windows endpoints to protect data at rest for compliance (PCI DSS, HIPAA, GDPR)
- Deploying BitLocker across enterprise fleet via Intune, SCCM, or GPO
- Configuring TPM-based encryption with PIN or USB startup key for enhanced security
- Managing BitLocker recovery keys in Active Directory or Azure AD

**Do not use** this skill for Linux disk encryption (use LUKS/dm-crypt) or macOS (use FileVault).

## Prerequisites

- Windows 10/11 Pro, Enterprise, or Education edition
- TPM 2.0 chip (recommended; TPM 1.2 supported with limitations)
- UEFI firmware with Secure Boot enabled (recommended)
- Separate system partition (200 MB minimum, created automatically by Windows installer)
- Active Directory or Azure AD for recovery key escrow

## Workflow

### Step 1: Verify TPM and System Requirements

```powershell
# Check TPM status
Get-Tpm
# ManufacturerId, ManufacturerVersion, TpmPresent, TpmReady, TpmEnabled

# Check TPM version (2.0 required for best compatibility)
(Get-WmiObject -Namespace "root\cimv2\security\microsofttpm" -Class Win32_Tpm).SpecVersion

# Check UEFI/Secure Boot
Confirm-SecureBootUEFI
# Returns True if Secure Boot is enabled

# Check BitLocker readiness
$vol = Get-BitLockerVolume -MountPoint "C:"
$vol.VolumeStatus  # Should be "FullyDecrypted"
$vol.ProtectionStatus  # Should be "Off"
```

### Step 2: Configure BitLocker GPO Settings

```
Computer Configuration → Administrative Templates → Windows Components → BitLocker Drive Encryption

Operating System Drives:
  - Require additional authentication at startup: Enabled
    - Allow BitLocker without compatible TPM: Disabled (enforce TPM)
    - Configure TPM startup: Allow TPM
    - Configure TPM startup PIN: Allow startup PIN with TPM
    - Configure TPM startup key: Allow startup key with TPM

  - Choose how BitLocker-protected OS drives can be recovered: Enabled
    - Allow data recovery agent: True
    - Configure storage of recovery information to AD DS: Enabled
    - Save recovery info to AD DS for OS drives: Store recovery passwords and key packages
    - Do not enable BitLocker until recovery information is stored: Enabled

  - Choose drive encryption method and cipher strength:
    - OS drives: XTS-AES 256-bit (Windows 10 1511+)
    - Fixed drives: XTS-AES 256-bit
    - Removable drives: AES-CBC 256-bit (for cross-platform compatibility)

Fixed Data Drives:
  - Choose how BitLocker-protected fixed drives can be recovered: Enabled
    - Store recovery passwords in AD DS: Enabled

Removable Data Drives:
  - Control use of BitLocker on removable drives: Enabled
  - Configure use of passwords for removable drives: Require complexity
```

### Step 3: Enable BitLocker - Command Line

```powershell
# Enable BitLocker with TPM-only protector (transparent to user)
Enable-BitLocker -MountPoint "C:" -EncryptionMethod XtsAes256 `
  -TpmProtector -SkipHardwareTest

# Enable BitLocker with TPM + PIN (recommended for laptops)
$pin = ConvertTo-SecureString "123456" -AsPlainText -Force
Enable-BitLocker -MountPoint "C:" -EncryptionMethod XtsAes256 `
  -TpmAndPinProtector -Pin $pin

# Add recovery password protector
Add-BitLockerKeyProtector -MountPoint "C:" -RecoveryPasswordProtector

# Backup recovery key to Active Directory
Backup-BitLockerKeyProtector -MountPoint "C:" `
  -KeyProtectorId (Get-BitLockerVolume -MountPoint "C:").KeyProtector[1].KeyProtectorId

# Encrypt fixed data drives
Enable-BitLocker -MountPoint "D:" -EncryptionMethod XtsAes256 `
  -RecoveryPasswordProtector -AutoUnlockEnabled
```

### Step 4: Deploy via Intune (Enterprise)

```
Intune → Endpoint Security → Disk encryption → Create Profile

Platform: Windows 10 and later
Profile: BitLocker

Settings:
  BitLocker base settings:
    - Encryption for operating system drives: Require
    - Encryption for fixed data drives: Require
    - Encryption for removable data drives: Require

  Operating system drive settings:
    - Additional authentication at startup: Require
    - TPM startup: Allowed
    - TPM startup PIN: Required (for high-security endpoints)
    - Encryption method: XTS-AES 256-bit
    - Recovery: Escrow to Azure AD

  Fixed drive settings:
    - Encryption method: XTS-AES 256-bit
    - Recovery: Escrow to Azure AD

  Assign to: All managed Windows devices (or specific groups)
```

### Step 5: Manage Recovery Keys

```powershell
# View recovery key on local system
(Get-BitLockerVolume -MountPoint "C:").KeyProtector |
  Where-Object {$_.KeyProtectorType -eq "RecoveryPassword"} |
  Select-Object KeyProtectorId, RecoveryPassword

# Retrieve recovery key from Active Directory (requires RSAT)
Get-ADObject -Filter {objectClass -eq "msFVE-RecoveryInformation"} `
  -SearchBase "CN=COMPUTER01,OU=Workstations,DC=corp,DC=example,DC=com" `
  -Properties msFVE-RecoveryPassword |
  Select-Object -ExpandProperty msFVE-RecoveryPassword

# Retrieve recovery key from Azure AD
# Azure Portal → Azure AD → Devices → [device] → BitLocker keys
# Or via Microsoft Graph API:
# GET /devices/{id}/bitlockerRecoveryKeys
```

### Step 6: Monitor Encryption Status

```powershell
# Check encryption status across fleet
manage-bde -status C:

# Expected output for encrypted drive:
#   Conversion Status: Fully Encrypted
#   Percentage Encrypted: 100.0%
#   Encryption Method: XTS-AES 256
#   Protection Status: Protection On
#   Key Protectors: TPM, Numerical Password

# PowerShell compliance check
$vol = Get-BitLockerVolume -MountPoint "C:"
if ($vol.ProtectionStatus -eq "On" -and $vol.VolumeStatus -eq "FullyEncrypted") {
    Write-Host "COMPLIANT: BitLocker enabled and fully encrypted"
} else {
    Write-Host "NON-COMPLIANT: BitLocker status - Protection: $($vol.ProtectionStatus), Volume: $($vol.VolumeStatus)"
}
```

## Key Concepts

| Term | Definition |
|------|-----------|
| **TPM (Trusted Platform Module)** | Hardware security chip that stores BitLocker encryption keys and provides measured boot integrity |
| **XTS-AES 256** | Encryption cipher used by BitLocker; XTS mode provides better protection for disk encryption than CBC |
| **Recovery Key** | 48-digit numerical password used to unlock BitLocker-encrypted drive when TPM authentication fails |
| **Key Protector** | Method used to unlock BitLocker (TPM, TPM+PIN, recovery password, startup key, smart card) |
| **Used Space Only Encryption** | Encrypts only sectors containing data; faster initial encryption but may leave remnant data in free space |
| **Full Disk Encryption** | Encrypts entire volume including free space; slower but more secure for drives that previously contained data |

## Tools & Systems

- **BitLocker (built-in)**: Windows full disk encryption feature
- **manage-bde.exe**: Command-line BitLocker management tool
- **BitLocker Recovery Password Viewer**: RSAT tool for viewing recovery keys in Active Directory
- **MBAM (Microsoft BitLocker Administration and Monitoring)**: Enterprise BitLocker management (legacy, replaced by Intune)
- **Microsoft Intune**: Cloud-based BitLocker policy deployment and recovery key management

## Common Pitfalls

- **Not escrowing recovery keys before encryption**: If recovery keys are not saved to AD/Azure AD before encryption, they may be permanently lost if the TPM fails.
- **Using TPM-only without PIN**: TPM-only mode is transparent but vulnerable to cold boot attacks and evil maid attacks. Add a startup PIN for laptops leaving the office.
- **Encrypting used space only on repurposed drives**: If a drive previously contained sensitive data, "used space only" encryption leaves deleted data unencrypted in free space. Use full disk encryption for repurposed drives.
- **Forgetting removable drives**: USB drives and external disks are common data loss vectors. Enforce BitLocker To Go for removable media.
- **No pre-provisioning for SCCM deployments**: Pre-provision BitLocker during OSD task sequence to encrypt before OS deployment, avoiding the lengthy post-deployment encryption process.