// For all SSE-S3 single-part objects we have to
		// fetch their decryption keys. We do this using
		// a Bulk-Decryption API call, if available.
		keys, err := crypto.S3.UnsealObjectKeys(ctx, k, metadata, buckets, names)
		if err != nil {
			return err
		}

		// Now, we have to decrypt the ETags of SSE-S3 single-part
		// objects and adjust the size and ETags of all encrypted
		// objects.