How To Get Google Cloud Storage S3 Interoperability Keys

Go to Cloud Storage Settings page in the Google Cloud Platform Console

Under Settings, select Interoperability

If you have not set up interoperability before, click Enable interoperability access.

Set the default project for interoperable access if it is not set (see this doc for more details)

Click Create a key under the access keys for your user account

Note: For production setups, Google recommends HMAC keys for a service account instead of a user account. Use "Create a key for a service account" on the same Interoperability tab.

Reference

• Google Cloud Platform: Migrating from Amazon S3 to Google Cloud Storage
• Set Up ObjectiveFS With Google Cloud Storage