Comments by JoJo82 - CodeProject

JoJo82 21-Jul-13 4:12am View

That looks promising. Am still trying to understand tho.
What kind of permission is that? How do I set it programmatically?
Can you explain more, maybe some sample code if possible so that I can better understand it and know how to apply it.
Thanks.

JoJo82 21-Jul-13 3:48am View

I did thought of that. However, due to the sensitivity of the information contained in the memorystream, i prefer not to save it to file if possible.

JoJo82 16-Jul-13 10:55am View

Thanks.. at least i know now where to start. I guess my question is answered now.

JoJo82 15-Jul-13 20:06pm View

I'm now at the very begining. My immediate task is to take XLSX1.xlsx and encrypt it.

Would I be on the right track if I were to follow the article http://support.microsoft.com/kb/307010 and http://www.codeproject.com/Articles/26085/File-Encryption-and-Decryption-in-C ? Which one would you recommend?

After I encrypt the file, would I be able to decrypt the file without saving it to hard disk? This is so that I can display the decrypted XLSX1.xlsx filestream in C# later.

JoJo82 15-Jul-13 12:43pm View

Doing as what you suggest would be possible if we're in the initial stage. Currently we already have many XLSX1.xlsx type file which contains the formulas etc and it would take a very long time to convert it to C#. Besides, my colleague is the one that does the excel programming/formula. During the development and design stage, he use Microsoft Excel to design the XLSX1.xlsx. That is why he need to save in Excel format, because everything is done in Microsoft Excel. Now that he already has the formula, he needs it to be protected.

In the future, when he need to change the formula in XLSX1.xlsx, I will decrypt it back to normal Microsoft Excel type file so my colleague can do the necessary changes and then encrypt it back again before ship it to customer.

Hope you understand why I need to do it as what I've written in the above.. Because we're stuck.. And now I'm stuck with the job of figuring out how to program it in C#.

Hope somebody can advice me. Thanks.

JoJo82 15-Jul-13 11:32am View

I have an xlsx file with formulas, graphs, protected information which I do not want my customer to see because those are IP. Lets call it XLSX1.xlsx. Because of that, I want to prevent it from being opened in Microsoft Excel or being opened anywhere. Even if the user were to rename the extension, they still will not be able to open it. That is why I need to encrypt it in such a way that even Excel's password cracker will not be able to crack it.

I have another xlsx file for the customer to enter their information. Lets call it XLSX2.xlsx.
This file, the user can open it normally with Microsoft Excel.

After the user has filled in the information in XLSX2.xlsx, they open my program. My program will decrypt XLSX1.xlsx and load it into filestream, get the necessary formula, do some calculation and then display the result in DSO framer or something. The user will then be able to and save the result in XLSX3.xlsx if they want to.

I hope this paints a much clearer picture of what I plan to do and why.
Thanks.

Comments by JoJo82 (Top 6 by date)