Protect Workbook with strong encryption password.

[ballgnm]

So there are many tutorials saying you can crack excel password with hex editor or just notepad.
I cracked my coworkers' forgotten password with that method.

But there were one file that I couldn't do that which was encrypted.

So I want to know how to protect file with that level of protection?

 

[6StringJazzer]

When you save the file, in the Save As dialog where you provide the filename, go to the lower left corner. Click on "Tools" (to the left of the Save button). Select General Options, and you will get a dialog to enter a password. When the file is saved, it will be encrypted using that password as a key. My understanding is that saving as .xlsb offers additional security since it is not stored in zip format.

There are discussions about this online but it is important to distinguish between passwords for VBA projects, sheet protection, and workbook encryption. The first two are easy to defeat because you can write code to brute-force the password. I think the third method is as secure as any other password scheme. However, I don't think there is any penalty for entering wrong passwords so this could probably be brute-forced too but it would have to have done external to the file (the first two can be done with VBA).

Another method is to encrypt the file outside of Excel altogether using a product like 7Zip.

 

[RoryA]

My understanding is that saving as .xlsb offers additional security since it is not stored in zip format

It's still zip format, but the contents of the zip are largely binary files, not plain XML.

 

[6StringJazzer]

Thanks, I never deconstructed one.