// z [i] = DES dec (rk(K cus , i), z [i−1] )
rk(key64, i, temp_output);
//y [i] = DES enc (rk(K cus , i), y [i−1] )
desdecrypt_iclass(temp_output,z[i-1], z[i]);
desencrypt_iclass(temp_output,y[i-1], y[i]);
// z [i] = DES dec (rk(K cus , i), z [i−1] )
rk(key64, i, temp_output);
//y [i] = DES enc (rk(K cus , i), y [i−1] )
desdecrypt_iclass(temp_output,z[i-1], z[i]);
desencrypt_iclass(temp_output,y[i-1], y[i]);