PURPOSE: To prevent an enciphered algorithm from being easily decoded, by performing the encipherment, or decoding by a code in which a non-linear processing is applied on a linear code.

CONSTITUTION: The titled device is provided with a linear code generator, for example, an M series code generator 3, and a nonlinear processing circuit, for example, a code conversion circuit 6, and the linear code from the linear code generator 3 is supplied to the non-linear processing circuit 6, and the encipherment, or the decoding of transfer data is performed by the output of the non-linear processing circuit. The code on which the non-linear processing is applied, is different from the linear code, and it is not easily decoded even when the transfer data, and an enciphered or decoded date are recognized. In this way, it is possible to prevent the enciphered algorithm from being easily decoded.