Customer-Managed Encryption Keys (CMEK):

CMEK allows you to manage encryption keys using Cloud Key Management Service (KMS). This gives you control over the lifecycle of the keys, including rotation, destruction, and auditing.

Set up a Cloud KMS key ring and create encryption keys that will be used to protect your data in BigQuery, Cloud SQL, and Cloud Storage.

Configure the services to use CMEK for encrypting data at rest, ensuring compliance with your organization's security policies.

Cloud External Key Manager (EKM):

Cloud EKM allows you to use keys managed by an external key management provider to encrypt data in Google Cloud services.

Integrate your external key management system with Google Cloud using supported protocols and APIs.

Configure your data warehouse services to use the external keys for encryption, ensuring that key management is handled outside of the Google Cloud environment.

Key Access Justifications:

Enable Key Access Justifications to provide visibility into why encryption keys are being accessed. This helps in monitoring and auditing key usage to ensure compliance and security.

Set up policies and logging to capture and review key access requests, providing insights into how and why keys are used.

Access Transparency and Approval:

Implement Access Transparency to gain visibility into Google’s access to your data and encryption keys.

Configure Access Approval to require explicit approval for Google support or engineering access to your data, adding an additional layer of security and control.