vSAN encrypts all user data at rest in VMware Cloud on AWS.
Encryption is enabled by default on each cluster deployed in your SDDC, and can't be turned off.
When you deploy a cluster, vSAN uses the AWS Key Management Service (AWS KMS) to generate a Customer Master Key (CMK), which is stored by AWS KMS. vSAN then generates a Key Encryption Key (KEK) and encrypts it using the CMK. The KEK is in turn used to encrypt Disk Encryption Keys (DEKs) generated for each vSAN disk.
You can change KEKs by using either the vSAN API or the vSphere Client UI. This process is known as performing a shallow rekey. Changing the CMK or DEKs is not supported. If you must change the CMK or DEKs, create a new cluster and migrate your VMs and data to it.