Import HSM-protected keys to Managed HSM (BYOK)

Azure Key Vault Managed HSM supports importing keys generated in your on-premises hardware security module (HSM); the keys will never leave the HSM protection boundary. This scenario often is referred to as bring your own key (BYOK). Managed HSM uses the Marvell LiquidSecurity HSM adapters (FIPS 140-2 Level 3 validated) to protect your keys.

Use the information in this article to help you plan for, generate, and transfer your own HSM-protected keys to use with Managed HSM.

For more information, and for a tutorial to get started using Managed HSM, see What is Managed HSM?.

Overview

Here's an overview of the process. Specific steps to complete are described later in the article.

• In Managed HSM, generate a key (referred to as a Key Exchange Key (KEK)). The KEK must be an RSA-HSM key that has only the import key operation.
• Download the KEK public key as a .pem file.
• Transfer the KEK public key to an offline computer that is connected to an on-premises HSM.
• In the offline computer, use the BYOK tool provided by your HSM vendor to create a BYOK file.
• The target key is encrypted with a KEK, which stays encrypted until it's transferred to the Managed HSM. Only the encrypted version of your key leaves the on-premises HSM.
• A KEK that's generated inside a Managed HSM isn't exportable. HSMs enforce the rule that no clear version of a KEK exists outside a Managed HSM.
• The KEK must be in the same managed HSM where the target key will be imported.
• When the BYOK file is uploaded to Managed HSM, a Managed HSM uses the KEK private key to decrypt the target key material and import it as an HSM key. This operation happens entirely inside the HSM. The target key always remains in the HSM protection boundary.

Prerequisites

To use the Azure CLI commands in this article, you must have the following items:

• A subscription to Azure. If you don't have one, you can sign up for a trial subscription.
• The Azure CLI version 2.12.0 or later. Run az --version to find the version. If you need to install or upgrade, see Install the Azure CLI.
• A managed HSM the supported HSMs list in your subscription. See Quickstart: Provision and activate a managed HSM using Azure CLI to provision and activate a managed HSM.

To sign in to Azure using the CLI, type:

az cloud set -n AzureChinaCloud
az login
# az cloud set -n AzureCloud   //means return to Public Azure.

For more information on login options via the CLI, take a look at sign in with Azure CLI

Supported HSMs

Vendor name	Vendor Type	Supported HSM models	More information
Cryptomathic	ISV (Enterprise Key Management System)	Multiple HSM brands and models including nCipher Thales Utimaco See Cryptomathic site for details
Entrust	Manufacturer, HSM as a service	nShield family of HSMs nShield as a service	nCipher new BYOK tool and documentation
Fortanix	Manufacturer, HSM as a service	Self-Defending Key Management Service (SDKMS) Equinix SmartKey	Exporting SDKMS keys to Cloud Providers for BYOK - Azure Key Vault
IBM	Manufacturer	IBM 476x, CryptoExpress	IBM Enterprise Key Management Foundation
Marvell	Manufacturer	All LiquidSecurity HSMs with Firmware version 2.0.4 or later Firmware version 3.2 or newer	Marvell BYOK tool and documentation
Securosys SA	Manufacturer, HSM as a service	Primus HSM family, Securosys Clouds HSM	Primus BYOK tool and documentation
StorMagic	ISV (Enterprise Key Management System)	Multiple HSM brands and models including Utimaco Thales nCipher See StorMagic site for details	SvKMS and Azure Key Vault BYOK
Thales	Manufacturer	Luna HSM 7 family with firmware version 7.3 or newer	Luna BYOK tool and documentation
Utimaco	Manufacturer, HSM as a service	u.trust Anchor, CryptoServer	Utimaco BYOK tool and Integration guide

Supported key types

Key name	Key type	Key size/curve	Origin	Description
Key Exchange Key (KEK)	RSA-HSM	2,048-bit 3,072-bit 4,096-bit	Managed HSM	An HSM-backed RSA key pair generated in Managed HSM
Target key
	RSA-HSM	2,048-bit 3,072-bit 4,096-bit	Vendor HSM	The key to be transferred to the Managed HSM
	EC-HSM	P-256 P-384 P-521	Vendor HSM	The key to be transferred to the Managed HSM
	Symmetric key (oct-hsm)	128-bit 192-bit 256-bit	Vendor HSM	The key to be transferred to the Managed HSM

Generate and transfer your key to the Managed HSM

Step 1: Generate a KEK

A KEK is an RSA key that's generated in a Managed HSM. The KEK is used to encrypt the key you want to import (the target key).

The KEK must be:

• An RSA-HSM key (2,048-bit; 3,072-bit; or 4,096-bit)
• Generated in the same managed HSM where you intend to import the target key
• Created with allowed key operations set to import

Use the az keyvault key create command to create a KEK that has key operations set to import. Record the key identifier (kid) that's returned from the following command. (You'll use the kid value in Step 3.)

az keyvault key create --kty RSA-HSM --size 4096 --name KEKforBYOK --ops import --hsm-name ContosoKeyVaultHSM

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Step 2: Download the KEK public key

Use az keyvault key download to download the KEK public key to a .pem file. The target key you import is encrypted by using the KEK public key.

az keyvault key download --name KEKforBYOK --hsm-name ContosoKeyVaultHSM --file KEKforBYOK.publickey.pem

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Transfer the KEKforBYOK.publickey.pem file to your offline computer. You'll need this file in the next step.

Step 3: Generate and prepare your key for transfer

Refer to your HSM vendor's documentation to download and install the BYOK tool. Follow instructions from your HSM vendor to generate a target key, and then create a key transfer package (a BYOK file). The BYOK tool will use the kid from Step 1 and the KEKforBYOK.publickey.pem file you downloaded in Step 2 to generate an encrypted target key in a BYOK file.

Transfer the BYOK file to your connected computer.

Step 4: Transfer your key to Managed HSM

To complete the key import, transfer the key transfer package (a BYOK file) from your disconnected computer to the internet-connected computer. Use the az keyvault key import command to upload the BYOK file to the Managed HSM.

az keyvault key import --hsm-name ContosoKeyVaultHSM --name ContosoFirstHSMkey --byok-file KeyTransferPackage-ContosoFirstHSMkey.byok

If the upload is successful, Azure CLI displays the properties of the imported key.

Next steps

You can now use this HSM-protected key in your Managed HSM. For more information, see this price and feature comparison.