Subscriber Jack Carmena wrote recently to ask about password-protecting files:
How do you password protect an existing file? I went to your website but couldn’t seem to locate that.
This is one of those "sometimes you can, sometimes you can’t" problems. In part, it depends on what type of file you are trying to protect.
Most programs do not allow you to password-protect a file. Some programs, like Word, Excel and PowerPoint, have built-in features that you can use to encrypt a file that you save.
Similarly, financial programs like Quicken, allow you to password-protect the data files they create.
The problem is that most programs don’t allow you to encrypt your data, nor handle decryption of data files, so you often have to work around the problem.
First, let’s look at Microsoft Excel and see what we can do there. Once you have created your spreadsheet, click on File > Save As from the menu bar, or click on the Save As button on the icon bar, if you’ve created one like I do. You’ll get the following dialog box.
The important spot is the Tools dropdown menu, at which you’d probably never look. When you click on Tools, pick the "General Options…", and you’ll get the chance to supply a password for opening the file.
You can also set a password for modifying the file, if you want to control that also. As usual, when you click the OK button, you’ll get another dialog box where you’ll retype your chosen password to make sure it’s the same.
But, what can you do if your chosen program doesn’t let you encrypt your data or otherwise prevent it from being read by someone else?
You can also encrypt any file in a round-about process, by taking advantage of the password-protection capabilities of a .zip compressed file. Windows XP has a built-in zip program — you can compress by right-clicking on a file, selecting Send To and then Compressed (zipped) File. Unfortunately, the zip program in Windows XP won’t let you apply a password.
Fortunately, though, the built-in unzip program in Windows XP will recognize when a password is necessary and will request the password when you try to unzip the file. With the unzipping part built into Windows, the question now is "how do we password-protect the file?"
Freeware to the rescue — the free compression program FilZip, which I use to handle a lot of different compression types, will zip and unzip. Even more important in this circumstance, it will allow you to password-protect the contents of the zip file.
When looking at the zip file with the Windows XP built-in unzip program, all looks normal — until you click on "Extract all files.&uquot; At that point, you get a dialog box that requires you to input the password that was used to encrypt the file.
Is there a way to have the encryption/decryption happen automatically in any program? I don’t know of any way to do that at this time.