Amazon RDS supports encryption at rest for all database engines, using keys you manage using AWS Key Management service. On a database instance running with Amazon RDS encryption, data stored at rest in the underlying storage is encrypted, as are its automated backups, read replicas, and snapshots. Encryption and decryption are handled transparently.
You can also add encryption to a previously unencrypted DB instance or DB cluster by creating a DB snapshot and then creating a copy of that snapshot and specifying a KMS encryption key. You can then restore an encrypted DB instance or DB cluster from the encrypted snapshot.