You may choose SSE-S3 if you prefer to have AWS manage your keys, as opposed to client-side encryption. Other server-side encryption methods offered by S3 are SSE-KMS, where the master key is managed by the customer, and SSE-C where the encryption is done with customer-provided keys where you manage the encryption keys and Amazon S3 manages the encryption, as it writes to disks, and decryption, when you access your objects.
