McEliece cryptosystem represents a smart open key system based on the hardness of the decoding of an arbitrary linear code, which is believed to be able to resist the advent of quantum computers. But the original McEliece cryptosystem, based on Goppa codes, has just very limited interest in practice, partly because it requires a very large public key. In this paper we propose a new general way to reduce the public key size. Unlike most papers on reducing key length of the cryptosystem, where original Goppa codes are substituted by some other codes, we suggest a new method of key size reduction which is code-independent.