Which encryption types can be used to protect objects at rest in Amazon S3?

 Server-side encryption with Amazon S3 managed encryption keys (SSE-S3) and server-side encryption with AWS KMS managed keys (SSE-KMS) are the encryption types that can be used to protect objects at rest in Amazon S3. Server-side encryption means that Amazon S3 encrypts the objects before saving them on disks and decrypts them when they are downloaded. SSE-S3 uses one master key per bucket that is managed by Amazon S3. SSE-KMS uses a customer master key (CMK) that is stored in AWS Key Management Service (AWS KMS) and provides additional benefits, such as audit trails and key rotation. For more information, see Protecting Data Using Server-Side Encryption and Protecting Data Using Encryption.