如何将熟知格式的二进制文件更改为自定义和不可发现的内容？

I have for example a zip-file. I need to change that file (I am thinking of file header or something, some bit or byte inside) to some custom format which then can't be unzipped. On the other side I would later be able to restore the original file using inverted algorithm. May anybody help me with that ?I have for example a zip-file. I need to change