DC/OS Minio supports S3 server-side-encryption (SSE). You can encrypt your data using SSE-C keys. In accordance with the S3 specification, the minio server will reject any SSE-C request made over an insecure (non-TLS) connection. This means that SSE-C requires TLS/HTTPS. You can start the Minio server with TLS using Security Section.
For more information on encrypting objects using SSE-C keys, please refer to How to use Minio server side encryption with AWS CLI.