>>>>>>>>>>Hi,
>>>>>>>>>>
>>>>>>>>>>I need to send someone a confidential document. Currently it is an Excel spreadsheet. I know it is impossible to make it 100% secure against all kinds of hackers. But 90% is good enough (or whatever it is). How can I encrypt this document? Should I convert it to a PDF and encrypt PDF? Or encrypting Excel is ok? I don't want to download and install any 3P tools, just whatever I have on my Windows 7. With the intent that the recipient will open it on a Mac computer.
>>>>>>>>>
>>>>>>>>>I'd work with the delivery method, rather than the document itself. For example, deliver it via a shared DropBox.
>>>>>>>>
>>>>>>>>I thought about it. But is Dropbox secure? That is, I can put this document in my Dropbox and give the recipient access to this folder/file. But then a hacker can hack my dropbox, no? I would prefer to do it over Dropbox but I never thought that it was very secure (maybe I am mistaken).
>>>>>>>
>>>>>>>Dropbox or other webstorage is IMO safer than sending via email, even if most email is encrypted on the way to your provider now.
>>>>>>>HTTPS:// into WebStorage much safer and if you schedule DL right after UL and delete after right that, chances are quite good thatthe file is really unreconstructible soon afterwards, esp. if you fill your quota on Dropbox with latest flicks hoping to cause at least partail overwrite if your disk quota is sector-linked to your login-data- which I doubt, but if part of encrypted file is overwritten,rest of file should be even safer ;-)
>>>>>>>Winzip has an option to encrypt, but that is deemed quite unsafe/easy to crack, no idea what that will do on the Mac side (unless there is a Windows-subsystem, which often is the case).
>>>>>>>
>>>>>>>Snowden et al go by PGP or Truecrypt follow ups - you stated that you do not want to DL/install something, which rules out the ways those I consider more knowing about the stuff than me use ;-)
>>>>>>>.
>>>>>>
>>>>>>Thank you. I will see if I can encrypt this spreadsheet right in the MS Excel and then place/copy it in the dropbox.
>>>>>
>>>>>An encrypted Excel file can be hacked in 2 seconds - I wouldn't do that if I were you. As I said the only known way to get into a .zip file is by brute force - and if you make the password long and strong enough it would take someone a few million years to get into it. PGP is a great way to go - but if you don't want to install anything like that then you can't use it.
>>>>
>>>>What is "PGP", just curious? And how do you hack an encrypted Exel, especially in 2 seconds? :)
>>>
>>>PGP stands for Pretty Good Privacy. This should explain it pretty well: https://ssd.eff.org/en/module/introduction-public-key-cryptography-and-pgp
>>>
>>>As far as removing the password from excel - this is how I've done it:
>>>Change the extension of file from .xlsx to .zip, open the .zip file and extract .xml file (it will be in folder xl/worksheets/sheet1.xml -- could be more than one), open the xml file with a text editor and remove the sheetprotection tag, put the xml file(s) back in the zip file, save it - then rename the .zip file back to .xlsx and taadaa--no more password.
>>
>>Thank you. Begs the question: why wouldn't MS, knowing this, make encryption more secure.
>
>Good question. All of the MS Office stuff is easy to defeat - outlook .pst files, word docs..etc etc.

Too bad.