Support for customer-supplied encryption keys was added in storage and we should support it as well. How to use such keys is documented [here](https://cloud.google.com/storage/docs/encryption#customer-supplied). Fields added to a blob are documented [here](https://cloud.google.com/storage/docs/json_api/v1/objects#customerEncryption).