Is this protection possible?

[DamonK]

We all know that sheets protected with passwords are never totally secure as there are a number of available password *******s for excel.

I had the thought that maybe it would be possible to have a worksheet that is not protected when saved but when it is opened there would be a sub-routine under Sub_Workbook Open that would step through each sheet and assign a random password. And when the workbook is saved it is saved without passwords again.

In this way there would be nothing for a password ******* to pick at. The only flaw I see would be that the password to open the VBA module would need to be static and this would open up the programming to change and remove. But wouldn't this be effective against most users who would only know about the utilities to open the passwords and not the programming behind excel?

Anyway that was my thought does anyone think this would be feasible and or useful?

 

[RoryA]

What would be needed for me to create a workbook and be reasonably comfortable that even if I post it online, that it won't be cracked

A strange definition of "reasonably comfortable".

To view one workbook does not require cracking the password, it requires breaking the encryption and there are online services that will gurarantee that. They won't retrieve the password though so you have to do the same decryption process for every workbook.

 

[MagiCat]

Reasonably comfortable in that it's likely that my password of "aSikec,e8*3e" will hold up.

I know that Excel uses an extremly weak encryption by default (which has worked to our advantage when we lost a password)

But also under Options/Security, I see many encryption types, RC4, Microsoft Strong Cryptographic Provider, RC4, Microsoft Enhanced RSA and AES Cryptographic Provider (Prototype) and many others. I'm guessing that using those would make it incompatible with Excel 2000 or 97, but would it make them unbreakable by the hacking programs in that it would take them years, not days?