var nonce [12]byte
		tmp := sha256.Sum256(fmt.Append(nil, uploadID, partID))
		copy(nonce[:], tmp[:12])

		partEncryptionKey := objectEncryptionKey.DerivePartKey(uint32(partID))
		encReader, err := sio.EncryptReader(reader, sio.Config{
			Key:   partEncryptionKey[:],
			Nonce: &nonce,
		})
		if err != nil {
			writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL)
			return
		}

	objectEncryptionKey, err := newEncryptMetadata(ctx, kind, keyID, key, bucket, object, metadata, cryptoCtx)
	if err != nil {
		return nil, crypto.ObjectKey{}, err
	}

	reader, err := sio.EncryptReader(content, sio.Config{Key: objectEncryptionKey[:], MinVersion: sio.Version20})
	if err != nil {
		return nil, crypto.ObjectKey{}, crypto.ErrInvalidCustomerKey
	}

	return reader, objectEncryptionKey, nil
}

}

// SealMD5CurrFn seals md5sum with object encryption key and returns sealed
// md5sum
type SealMD5CurrFn func([]byte) []byte

// PutObjReader is a type that wraps sio.EncryptReader and
// underlying hash.Reader in a struct
type PutObjReader struct {
	*hash.Reader              // actual data stream
	rawReader    *hash.Reader // original data stream
	sealMD5Fn    SealMD5CurrFn
}