In Windows would it be possible to protect data within a single program? I have been looking into CryptProtectData but whis is by user basis I would like something simular but on program basis. My program will have multiple users that require access to the same data, but the data is sentitive and I dont want any user to read it.
First of all, if your user has administrator privileges, there is no definite way to keep them out.
Second, even if they didn't, you'd have to implement part of your software at ring 0, so it would have a higher privilege than the user, which would make it harder for them to get access to the process' memory or executables. You could then encrypt your data and decrypt it when you serve it to the user.
If all of the above is not possible, you can employ the same obfuscation techniques that software developers use against cracking.
That usually comes down to preventing debugging or preventing patching. Some advice here: http://www.woodmann.com/crackz/Tutorials/Protect.htm