Linear transformation for symmetric-key ciphers

In a symmetric-key encryption method of the linear transformation matrix a, including a binary [n,k,d] error-correcting codes, including k<n<2k, and d is the minimum distance of binary error-correcting codes. The code consists of a standard format G= (Ik| | B) generator matrix g ∈ Z2kxn. 2k-n expand the matrix b of the resulting matrix c is odd. C export linear transformation matrix from the matrix a. Optimally, error-correcting codes based on the XBCH code.