This document provides information about configuring our HSMs with HashiCorp Vault by using PKCS #11 libraries. For additional questions about your HSM, see the relevant administrator guide.
Application description
Vault Enterprise integrates with Hardware Security Module (HSM) platforms to provide the following functionality:
| Functionality | Description |
|---|
| Master Key Wrapping | Vault protects its master key by transiting it through the HSM for encryption rather than splitting it into key shares. |
| Automatic Unsealing | Vault stores its encrypted master key in storage, allowing for automatic unsealing. |
| Seal Wrapping | Seal wrapping to provide FIPS KeyStorage-conforming functionality for Critical Security Parameters. |
| Entropy Augmentation | Enables Vault to leverage the HSM for augmenting system entropy. |
Vault creates two AES-256 keys on the HSM: One for encrypting and decrypting and the other for generating and verifying MACs.
Master Key Wrapping and Automatic Unsealing
In some large organizations, designating key officers who must be available to unseal Vault installations can be complex because the most common pattern is to deploy Vault immutably. Thus, automating unseal by using an HSM provides a simplified yet secure way of unsealing Vault nodes as you deploy them.
Vault pulls its encrypted master key from storage and transits it through the HSM for decryption by using the PKCS #11 API. After it decrypts the master key, Vault uses the master key to decrypt the encryption key to resume Vault operations.
Seal Wrapping
Vault encrypts secrets by using 256-bit AES in GCM mode with a randomly generated nonce before writing them to its persistent storage. When you enable Seal Wrap, Vault wraps your secrets with an extra layer of encryption, leveraging the HSM encryption and decryption.
Benefits of the Seal Wrap
Seal Wrap has the following benefits:
- Conforms with FIPS 140-2 directives on Key Storage and Key Transport as certified by Leidos.
- Supports FIPS level of security equal to HSM.
- For example, if you use Level 3 hardware encryption on an HSM, Vault uses FIPS 140-2 Level 3 cryptography.
- Enables you to deploy Vault in high-security Governance, risk management, and compliance (GRC) environments (for example, PCI-DSS, HIPAA) where FIPS guidelines are important for external audits.
- Provides a pathway for using Vault in managing Department of Defense’s (DOD) or North Atlantic Treaty Organization (NATO) military secrets.
Entropy Augmentation
Entropy Augmentation enables Vault to leverage the HSM for augmenting system entropy.
With Entropy Augmentation enabled, the following keys and tokens leverage the configured external entropy source.
| Operation | Description |
|---|
| Master Key | The AES key encrypted by the seal mechanism. This key encrypts the key ring. |
| Key Ring Encryption Keys | The keys that encrypt all of the Vault storage are embedded in the Vault keyring. |
| Recovery Key | With auto-unseal, use the recovery keys to regenerate the root token, key rotation, and so on. |
| TLS Private Keys | For HA leader, Raft and Enterprise Replications. |
| MFA TOTP Keys | The keys used for TOTP in Vault Enterprise MFA |
| JWT Signing Keys | The keys used to sign wrapping token JWTs. |
| Root Tokens | Superuser tokens grants access to all operations in Vault. |
| DR Operation Tokens | Token that allows certain actions to be performed on a DR secondary. |
The transit secrets engine manages several different key types and leverages the keysutil package (godoc.org/github.com/hashicorp/vault/sdk/helper/keysutil) to generate keys. It uses the external entropy source for key generation.
Guardian integration
The Guardian Series 3 introduces mission-critical viability to core cryptographic infrastructure, including:
- Centralization of device management
- Elimination of points of failure
- Distribution of transaction loads
- Group-specific function blocking
- User-defined grouping systems
See the applicable guide in the Futurex Portal for configuring HSMs with the Guardian Series 3, including PKCS #11 and CNG configuration. 
