storage.py 文件源码

def decode_block(self, block_id, block_data):
        assert (isinstance(block_id, bytes)
                and len(block_id) == self.block_id_len)
        assert isinstance(block_data, bytes)
        assert len(block_data) > (len(self.magic) + self.iv_len + self.tag_len)

        dec = Decoder(block_data)

        # check magic
        assert dec.decode_bytes(len(self.magic)) == self.magic

        # get iv
        iv = dec.decode_bytes(self.iv_len)

        # get tag
        tag = dec.decode_bytes(self.tag_len)

        c = Cipher(algorithms.AES(self.key), modes.GCM(iv, tag),
                   backend=self.backend)
        d = c.decryptor()
        d.authenticate_additional_data(block_id)

        s = d.update(dec.decode_bytes_rest()) + d.finalize()
        return s