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SQL*XL: Database to Excel bridge litLIB: Excel power functions pack ExcelLock: Locking and securing your valuable Excel spreadsheets encOffice: Protect your Excel file easy and safe encOffice: Protect your Excel file easy and safe
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Secure spreadsheet and hide formulas (Read 2989 times)
Gerrit-Jan Linker
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Posts: 75
Secure spreadsheet and hide formulas
11.08.09 at 22:28:56
Secure spreadsheet and hide formulas
I plan to sell excel spreadsheets that I wrote for calculating scientific data as part of my book. I understand how to use your software (encOffice) to protect them, but once the user opens the spreadsheet, can't they share the spreadsheet with someone else? I also don't want the formulas to be accessable. I know how to hide formulas but worry that they are not very secure.

I understand your worry. It is difficult to protect against illegal copying and to hide your valuable research. There are a couple of things to consider. I can help with these if required.  
Prevent illegal distribution
This is difficult to do but not impossible. You can force the spreadsheet only to be opened from a CD for example or you can create personalised registration keys that make visible to whom the spreadsheet is registered.  
Prevent viewing certain sheets.  
You could place formulas on a separate sheet that you hide. When you protect the workbook with a password (that you could generate with encOffice for example) the sheets cannot be made visible again.  
Prevent viewing sheets (2)
Using code you can hide sheets so they can only be unhidden also usig code. So the normal unhide does not work.  
Prevent viewing certain cells.  
You can hide cells so formulas are not visible. A simple reference will enable you to display the outcome though. E.g. =D12 when you have hidden the formula in D12. Worksheet protection prevents the user undoing this. A password can again be created with encOffice.  
Convert formulas into a dll.
This is a very secure way in which you replace the formulas with a function call. The function will call a dll that computes the value. A dll cannot be reverse engineered.  
There are also some options to temporarily remove all Excel's toolbars and menus so the user cannot do anything else but view your file.  
You can also create a small viewer application so all access to the file is controlled.  
I have given quite some options above. Bottom line is that you cannot do it 100% save but you can apply a reasonable security. Please let me know what you like to discuss further.  
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Gerrit-Jan Linker
Linker IT Software
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