Excel to Calc - Protection

[burton_n]

I have created an Excel spreadsheet (with hidden tables and formulae) that has been password protected. That file was sent onto a customer who uses Openoffice. He was able to open the spreadsheet and view the hidden information in Openoffice, even though it was protected in Excel. I wondered whether anyone had encountered anything similar and whether there was any way around it?

Thank you

[Villeroy]

Excel's protection mechanisms don't provide any security at all as you can see. The encrypted password is saved within the document. I believe it is impossible to decrypt the password to compare it with the one given by the user. But it is possible indeed to simply ignore the password protection.
OOo is different. The password is used to encrypt the file's content. The encryption is done by means of some standard algorithm so other applications can use the same algorithm in order to provide the same functionality, which is what Microsoft intentionally tries to avoid for it's own obfuscated document formats.

[TerryE]

Broadly password protection schemes divide themselves into two categories: strong in which the application use proper cryptographic techniques to ensure that the document or material is protected by some encoding scheme that is not practically decodable without the key except by a brute-force guessing technique that becomes computationally infeasible for individuals within lifetimes; and weak which use some form of obfuscation scheme to prevent the casual user accessing the data. The problem with weak schemes is that the determined hacker with the right tools can easily access the data. In the case of Excel, these are trivially available over the Internet. (Google "+Excel +Protection (removal OR crack*)" for a list of such tools.)

OpenOffice therefore ignores such weak mechanisms. Sorry but that's a design decision. The point here is that the programme has to be able to use the contents of the protect sheets (and therefore access the content without the user typing in the content), so options will by definition be weak, and therefore trivially readable anyway.

If you want to share data with other parties then any data that you send to that party will be accessible unless protected by strong encryption. The safest way to protect such data in these circumstances would be not to send the data to the party in the first place. A good way of doing this is to use external sheet linking, e.g. divide your sheet into two parts: one containing the data you want to share, and the other spreadsheet the data, formulae and macros that you want to keep private, with cross spreadsheet linking to maintain the overall application functionality. Send the first to your customer; keep the second in-house. The customer can use and access the first but not the second. Why? because only you have that copy. If the common content is a standard set of "reference" data and macros, then the best method of maintaining this is in a template or add-on.

Sorry that I can't help you more, but this is really a free service by volunteers for OOo users. I am sure that if you work for a large enterprise then the $Ms that it spends on MS support will enable you to get more detailed support on Excel from Microsoft