Password Protecting a workbook

[Maryann]

There are two ways to put a password on an Excel workbook - one is through
Prepare Encrypt and the other through the Tools menu in the Save As dialog
box. Why would I choose Prepare Encrypt rather than just put on a password
through the Save As command? What extra protection do I get, if any? If
someone gets my password - they can open the file with either method.

 

[Jim Thomlinson]

The protection through SaveAs can be hacked for a small fee.

 

[JLatham]

There's a lot that could be said in answering your question. But to try to
put it into a nutshell:
Yes - one password to protect/encrypt/decrypt/unprotect. But consider the
level of difficulty in cracking the password if you choose to use 128-Bit
encryption. Much more difficult than the 40-bit process used just to
password protect (without encryption). So keep your password in a secure
place - but you definitely want a record of it just in case you go for a long
period without using the workbook and suddenly encounter a bad case of CRS
when you need that password again.

While you can typically, and with free tools, protect workbook (unencrypted)
password in minutes, not so easy with encrypted workbook and a long, strong
password: lets say at least 8 characters, contains both upper and lower case
characters, at least one numeric digit and some non alpha-numeric
character(s).

Microsof also claims even stronger protection if you password protect with
encryption and save in the open-xml format.