Which method provides a secure way to authenticate service accounts to GCP products via Compute Engine VM credentials?

Using the instance's service account Application Default Credentials is a secure method for authenticating service accounts to Google Cloud Platform (GCP) products via Compute Engine VM credentials. Each Google Cloud VM instance can be associated with a service account, which grants the instance the necessary permissions to access GCP resources. When applications running on the VM utilize the Application Default Credentials, they automatically authenticate against the Google Cloud API using the permissions assigned to the instance's service account.

This approach simplifies the authentication process, as it eliminates the need for developers to manage and securely store access keys or credentials within the application code or environment. By leveraging the instance's service account, the application can seamlessly and securely interact with other GCP services without any additional authentication steps, provided that the necessary IAM permissions are configured.

In contrast to the other options, which pose security risks or involve complex management tasks, using the instance's service account provides a more streamlined and secure way to authenticate. For instance, HTTP signed URLs may offer temporary access to specific resources but do not support broader resource access management. Generating a P12 file could introduce security vulnerabilities if not handled carefully, while committing JSON credential files to a source repository is highly discouraged due to the risk of exposing sensitive information. Thus, the use