Your app on Compute Engine needs Google service account credentials on the VM hosts. What is the most secure way to provide credentials to the VMs?

The most secure and recommended way to provide Google service account credentials to Compute Engine VMs is by using the VM instance's service account with Application Default Credentials (ADC). When a service account is attached to a VM instance, applications running on that VM can automatically obtain credentials for authorized Google Cloud services without needing to store or manage credential files manually. This method leverages Google Cloud's built-in identity and access management, minimizing the risk of credential exposure. Using signed HTTP URLs to deliver credentials is less secure as it involves transferring sensitive data. Generating a P12 key and copying it to the VM or committing credential JSON to a source repo are highly insecure practices. These methods involve storing static credential files, which are susceptible to theft if the VM or repository is compromised, and they make credential rotation difficult.