  This paper proposes an efficient secret key cryptosystem based on polar codes
over Binary Erasure Channel. We introduce a method, for the first time to our
knowledge, to hide the generator matrix of the polar codes from an attacker. In
fact, our main goal is to achieve secure and reliable communication using
finite-length polar codes. The proposed cryptosystem has a significant security
advantage against chosen plaintext attacks in comparison with the Rao-Nam
cryptosystem. Also, the key length is decreased after applying a new
compression algorithm. Moreover, this scheme benefits from high code rate and
proper error performance for reliable communication.
