Google Cloud External Key Manager Resources
Google Cloud External Key Manager (EKM) is a cloud native service that provides access to an external key encryption key (KEK) for use as a wrapping key in Google Cloud Platform (GCP) Projects. CCKM integration with Google Cloud EKM enables you to:
Manage endpoints for KEKs for keys added to the key ring through GCP EKM
The AES256 wrap/unwrap KEK allows users, developers, and organizations to maintain separation between encrypted data at rest and encryption keys.
The benefits of using CCKM Google Cloud EKM Endpoints include:
Secure generation, storage and protection of your KEK.
Privately maintained key provenance, managed access control, and centralized key management.
Full life cycle management of your encryption key.
Visibility for compliance.
GCP allows users to use Cloud External Key Management (EKM) in the Google Cloud Key Management Service (KMS) for Google Projects. CCKM protects your data in the GCP while your encryption keys are stored in CipherTrust Manager outside of GCP. Users create a Key Encryption Key (KEK) in CCKM, create a Cloud EKM key in Google Cloud, using the KEK's URI to identify the externally-managed key in Google Cloud KMS, and use the keys to protect data in a Customer-Managed Encryption Key (CMEK) integration service, to encrypt data using a symmetric key, or to sign with an asymmetric key. In this scenario, Google Cloud KMS does not store the external key material.
The following diagram shows how the Cloud KMS and CCKM fit into the key management model, using BigQuery and Compute Engine as example services.
Note
If you are deploying a new CipherTrust Manager instance exclusively or primarily to use the Google Cloud EKM service, we recommend deploying the instance geographically close to one of the Google Cloud KMS regions where you intend to set up the Google Cloud KMS Key Ring.
We have tested the following Google Customer-Managed Encryption Key (CMEK) integration services for Google Cloud EKM:
BigQuery
Compute Engine
All other Google CMEK integration services for Google Cloud EKM are not validated by Thales, but are expected to work and are supported. Consult Google EKM documentation for the full list of Google CMEK services for EKM. Only CMEK services integrated with Google Cloud EKM are supported with CCKM EKM endpoints.
These are "Hold Your Own Key" (HYOK) integrations, where you manage and control the base KEK inside of CCKM. Google Cloud has additional CMEK services that do not follow the HYOK model and do not integrate with EKM.
Ubiquitous Data Encryption
CCKM provides another integration with EKM, called Google Cloud External Key Manager Ubiquitous Data Encryption (EKM UDE). While standard EKM protects data in use for CMEK services in Google Cloud, EKM UDE protects data as it moves between two environments, called workloads, mediated by Google Cloud KMS. The two workloads can be two Google Cloud Confidential VMs, two non-confidential environments (on-premises or cloud), or one Confidential VM and one non-confidential environment.
CCKM provides options in the EKM UI menus to manage endpoints, configure and manage policy sets, and configure confidential computing requirements for access to KEKs.
The UDE version of EKM provides additional security, access control and auditability guarantees, namely:
the end-to-end encryption of Data Encryption Keys (DEKs) between workloads and the external key manager
the leveraging of Confidential VMs to provide strong guarantees of the runtime privacy of customer data (data-in-use security)
the use of independently-verifiable attestations of the runtime environment, allowing the EKM to strongly differentiate between protected and unprotected environments
An example architecture is shown below, showing a potential interaction between CCKM, Google Cloud Storage, and a Confidential VM. For any type of workload, CCKM holds the KEK needed to wrap and unwrap DEKs. Communications between CCKM and a Confidential VM require an Attestation of Confidentiality sequence for an additional guarantee that only the intended workload can access the KEK.
These CipherTrust Cloud Key Manager keys can be used in four main use cases within GCP:
A DEK is generated within a GCP confidential VM, then is wrapped by the CCKM KEK. The KEK is configured such that unwrapping of the wrapped key is only possible by an attested, verified confidential VM. You can place additional restrictions on instance ID, project ID, and zones, which limit KEK use to specific confidential VMs.
A DEK is generated on-premise, in a regular (non-confidential computing) environment, then is wrapped by the CCKM KEK. The data is uploaded to Google Cloud Storage (GCS) and the KEK is configured such that unwrapping of the wrapped key (and hence the protected data) is only possible by an attested, verified confidential VM. You can place additional restrictions on instance ID, project ID, and zones, which limit KEK use to specific confidential VMs.
A DEK is generated within a GCP confidential VM, then is wrapped by the CCKM KEK. The KEK is configured such that wrapping of the wrapped key is only possible in an attested, verified confidential VM, but that unwrapping is possible in a regular (non-confidential computing) environment. You can place additional restrictions on instance ID, project ID, and zones, which limit KEK use to specific confidential VMs.
A DEK is generated on-premise in a regular environment, then is wrapped by CipherTrust-managed KEK. The data is moved to another regular environment (on cloud or on-premise). The KEK is configured such that unwrapping of the wrapped data is possible in a second regular environment.
These four cases, respectively, give the following guarantees:
In case 1, the guarantee that the protected DEK/data is only accessible by a confidential VM.
In case 2, the guarantee that data encrypted on-premise and migrated to the cloud will only be accessible by a confidential VM.
In case 3, the guarantee that data retrieved from the cloud and decrypted, was originated in a confidential VM.
In case 4, the guarantee is that the data is only decryptable when the KEK is accessible.
