}
	stream, err := metadata.Algorithm.Stream(key)
	if err != nil {
		return nil, err
	}
	if stream.NonceSize() != len(metadata.Nonce) {
		return nil, sio.NotAuthentic
	}
	return stream.DecryptReader(ciphertext, metadata.Nonce, nil), nil
}

type encryptedObject struct {
	KeyID  string `json:"keyid"`
	KMSKey []byte `json:"kmskey"`

	Algorithm sio.Algorithm `json:"algorithm"`

	return newDecryptReaderWithObjectKey(client, objectEncryptionKey, seqNumber)
}

func newDecryptReaderWithObjectKey(client io.Reader, objectEncryptionKey []byte, seqNumber uint32) (io.Reader, error) {
	reader, err := sio.DecryptReader(client, sio.Config{
		Key:            objectEncryptionKey,
		SequenceNumber: seqNumber,
	})
	if err != nil {
		return nil, crypto.ErrInvalidCustomerKey
	}
	return reader, nil
}