In the context of server-side encryption handled by cloud providers, the data is encrypted after transmission to the cloud using either provider-managed keys or customer-managed keys. The cloud provider takes responsibility for encrypting the data when it is stored in the cloud, ensuring that the data at rest is protected.

Server-side encryption typically uses symmetric encryption for performance reasons, but this attribute is not what defines the encryption process. Also, server-side encryption focuses on protecting data once it's in the cloud, not before transmission. Encryption in transit is typically handled separately from server-side encryption and applies to data as it moves between the client and the cloud.