I have users entering data onto a page, at the end of the page, the page is
password protected to prevent changes. The file needs to be with the user to
view data.

Being a real paranoid ! I want to be able to detect if someone has altered
the data by hacking the password for example.

What i want to do is at the bottom of the page print a certain value which
is directly dependent on the data on the page. E.g No of Characters, No of
vowles, No of bytes of data or something else (unknown to the user), So if
someone was to manipulate the data it can be detected by cross checking
against this value.

Hope i make sense.

Any Sherlock Holmes out there

Sunil