How can we ensure that the iXBRL file remains unaltered?

When an iXBRL file is created, each  iXBRL file as well as each folder within the file is equipped with a hashcode. If anything is changed within the file, the hashcode changes too. That way you can compare different versions of the same file and see not only if something has been changed, but also in which section it was changed.

When you open your file in the ParsePort XBRL Inspector, you can find the hashcode in the Validation pane under "General Information". Also, if you scroll down to the "zip content" section you can find the hash codes for the different folders within the zip package.