Copies of Amazon Elastic Block Store (Amazon EBS) Snapshots encrypted under a custom Customer Managed Key (CMK) are now incremental. This means that when you make a new copy of an EBS Snapshot, only the modified chunks compared to the previous copy of the same EBS Snapshot are saved in the new copy. This minimizes the time required to copy the EBS Snapshot and saves on storage costs by not duplicating data for such EBS Snapshots encrypted with custom CMK. This is similar to what we already support for copies of unencrypted EBS Snapshots and copies of EBS Snapshots encrypted under your default CMK.
