x963kdf.py 文件源码

def derive(self, key_material):
        if self._used:
            raise AlreadyFinalized
        self._used = True

        if not isinstance(key_material, bytes):
            raise TypeError("key_material must be bytes.")

        output = [b""]
        outlen = 0
        counter = 1

        while self._length > outlen:
            h = hashes.Hash(self._algorithm, self._backend)
            h.update(key_material)
            h.update(_int_to_u32be(counter))
            if self._sharedinfo is not None:
                h.update(self._sharedinfo)
            output.append(h.finalize())
            outlen += len(output[-1])
            counter += 1

        return b"".join(output)[:self._length]